JP7521430B2 - Substrate for light emitting element and method for producing same - Google Patents

Description

The present invention relates to a substrate for a light-emitting element and a method for manufacturing the same.

Light-emitting elements such as light-emitting diodes (LEDs) and semiconductor laser diodes (LDs) are widely used in automotive lighting, displays, street lighting, etc. The light-emitting elements are mounted on a light-emitting element substrate equipped with various wiring and used as light-emitting devices.

In recent years, there has been a demand for higher brightness for light-emitting devices, and this has led to a tendency for the amount of heat generated by the light-emitting elements to increase. Therefore, in order to suppress the temperature rise of the light-emitting elements due to the increased amount of heat generated, a heat sink is installed on the substrate for the light-emitting elements.

JP 2015-86090 A JP 2014-154547 A JP 2004-199941 A

Typically, silver is used as a heat sink provided on a substrate for a light-emitting element. However, silver is easily sulfurized, and once sulfurized, there is a problem that the properties of the heat sink deteriorate. In particular, in the case of light-emitting devices for automobiles, where sulfur components can be contained in exhaust gases, such sulfurization problems can become a problem that cannot be ignored.

Therefore, it is possible to consider using copper as an alternative material to silver.

However, copper does not have good adhesion to the base that constitutes the substrate for the light-emitting element. For this reason, when using copper as a heat sink, it becomes necessary to further add glass frit to improve adhesion to the base.

However, when glass frit is added to a heat sink, there is a problem that the resistivity of the heat sink increases and the thermal conductivity of the heat sink decreases.

The present invention has been made in view of the above background, and aims to provide a substrate for a light-emitting element that is resistant to deterioration due to sulfurization, has good adhesion to the base, and is provided with a heat sink with significantly reduced resistivity. Another aim of the present invention is to provide a method for manufacturing such a substrate for a light-emitting element.

In the present invention, there is provided a substrate for a light-emitting element,
a base having a first main surface and a second main surface opposed to each other, a first hole having an opening in the first main surface and a second hole having an opening in the second main surface, the first main surface being a side on which a light emitting element is provided;
a heat sink disposed in the first and second holes of the substrate, the heat sink being electrically connected from the first hole to the second hole;
having
the substrate includes a mixed material of glass and ceramics, and 90% by volume or more of the glass is amorphous;
The heat sink is formed of copper at 99% by mass or more, thereby providing a substrate for a light emitting element.

The present invention also provides a method for producing a substrate for a light-emitting element, comprising the steps of:
(I) preparing a first green sheet having a through hole,
the first green sheet comprises a mixed material of glass and ceramics;
(II) filling the through holes of the first green sheet with a heat sink paste,
the paste for heat sink contains copper particles and is substantially free of glass frit;
(III) combining the first green sheet filled with the heat sink paste with another green sheet containing the mixed material to form an assembly;
(IV) firing the assembly to form a substrate for a light-emitting device,
A substrate containing glass and ceramics is formed from the first green sheet and the other green sheets, and the glass contained in the substrate is amorphous in an amount of 90 volume % or more;
forming a heat sink containing 99% by mass or more of copper from the heat sink paste;
A method of manufacturing is provided, comprising:

The present invention can provide a substrate for a light-emitting element that is resistant to deterioration due to sulfurization, has good adhesion to the base, and is equipped with a heat sink with significantly reduced resistivity. The present invention can also provide a method for manufacturing such a substrate for a light-emitting element.

1 is a schematic top view of a substrate for a light emitting device according to an embodiment of the present invention; 2 is a schematic cross-sectional view taken along line AA of the light-emitting element substrate according to one embodiment of the present invention shown in FIG. 1. FIG. 2 is a schematic cross-sectional view of a substrate for a light-emitting device according to another embodiment of the present invention. 1A to 1C are diagrams illustrating an example of a flow of a method for manufacturing a substrate for a light-emitting element according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a process for producing a substrate for a light-emitting element by a method for producing a substrate for a light-emitting element according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a process for producing a substrate for a light-emitting element by a method for producing a substrate for a light-emitting element according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a process for producing a substrate for a light-emitting element by a method for producing a substrate for a light-emitting element according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a process for producing a substrate for a light-emitting element by a method for producing a substrate for a light-emitting element according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a process for producing a substrate for a light-emitting element by a method for producing a substrate for a light-emitting element according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a process for producing a substrate for a light-emitting element by a method for producing a substrate for a light-emitting element according to an embodiment of the present invention.

Below, one embodiment of the present invention is described with reference to the drawings.

As mentioned above, when copper is used as a heat sink material to replace silver, which has a sulfuration problem, in a substrate for a light-emitting element, the adhesion between the base and the heat sink may decrease. Therefore, in order to improve the adhesion between the base and the heat sink, it becomes necessary to further add glass frit to the heat sink.

However, when glass frit is added to a heat sink, the resistivity of the heat sink increases, resulting in a problem of reduced thermal conductivity of the heat sink.

In contrast, in one embodiment of the present invention,
A substrate for a light-emitting element,
a base having a first main surface and a second main surface opposed to each other, a first hole having an opening in the first main surface and a second hole having an opening in the second main surface, the first main surface being a side on which a light emitting element is provided;
a heat sink disposed in the first and second holes of the substrate, the heat sink being electrically connected from the first hole to the second hole;
having
the substrate includes a mixed material of glass and ceramics, and 90% by volume or more of the glass is amorphous;
The heat sink is formed of copper at 99% by mass or more, thereby providing a substrate for a light emitting element.

In the substrate for light-emitting elements according to one embodiment of the present invention, the heat sink is made of 99% or more by mass of copper. Therefore, one embodiment of the present invention has the characteristic that the heat sink is less susceptible to deterioration due to sulfurization compared to conventional heat sinks made of silver.

In addition, in the substrate for a light-emitting element according to one embodiment of the present invention, the heat sink is substantially free of glass frit. Here, the term "substantially free" means that the target component is contained in an amount of less than 1% by mass, preferably 0.5% by mass or less.

Therefore, in a substrate for a light-emitting element according to one embodiment of the present invention, the increase in resistivity of the heat sink due to the addition of glass frit can be significantly suppressed.

In addition, in a substrate for a light-emitting element according to one embodiment of the present invention, the base comprises a mixed material of glass and ceramics, and 90% or more by volume of the glass is amorphous.

If the majority of the glass constituting the substrate, i.e., 90% or more by volume, is amorphous, the adhesion between the copper heat sink and the substrate can be significantly improved.

Therefore, when such a base is used, it is possible to properly adhere the base and the heat sink to each other even if the heat sink is made of copper and contains substantially no glass frit.

Due to the above effects, in one embodiment of the present invention, a substrate for a light-emitting element can be provided that is less susceptible to deterioration due to sulfurization, has good adhesion to the base, and is equipped with a heat sink with significantly reduced resistivity.

(Substrate for light-emitting element according to one embodiment of the present invention)
Hereinafter, a substrate for a light emitting device according to an embodiment of the present invention will be described in detail with reference to the drawings.

Figure 1 shows a schematic top view of a substrate for a light-emitting element according to one embodiment of the present invention. Figure 2 shows a schematic cross section along line A-A of the substrate for a light-emitting element shown in Figure 1.

As shown in Figures 1 and 2, a substrate for a light-emitting element according to one embodiment of the present invention (hereinafter referred to as a "first substrate for a light-emitting element") 100 has a base 110 and a heat sink 140.

The base 110 has a roughly box-like shape with the top surface removed, and can accommodate a light-emitting element (not shown) inside the box to support the light-emitting element.

As shown in FIG. 1, the base 110 is generally rectangular when viewed from above and has four sides, namely a first side 112a to a fourth side 112d.

Also, as shown in FIG. 2, the base 110 has a side portion 115 and a bottom portion 120 located below the side portion 115.

Side portion 115 has a "frame" shape with the central portion removed, and has four portions corresponding to first side 112a to fourth side 112d, i.e., first portion 115a to fourth portion 115d.

The bottom 120 has a first main surface 122 and a second main surface 124 facing each other, and the side 115 is disposed on the first main surface 122 of the bottom 120. A light-emitting element (not shown) is disposed on the first main surface 122 of the bottom 120 in a space portion surrounded by the side 115.

The bottom 120 also has a first hole 125a having an opening on the first main surface 122 and a second hole 125b having an opening on the second main surface 124.

In the example shown in Figure 2, the first hole 125a and the second hole 125b are connected to each other, thereby forming a through portion 126 that connects from the first main surface 122 to the second main surface 124 of the bottom 120.

1 and 2, the cross section of the through-hole 126 perpendicular to the extension direction is substantially rectangular. However, this is merely an example, and the shape of the cross section perpendicular to the extension direction of the through-hole 126 is not particularly limited.

In this application, "approximately rectangular" means, for example, that the four corners of the rectangle are rounded, as shown in the through-hole 126 and heat sink 140 in Figure 1.

The heat sink 140 is filled into the through-hole 126 of the base 110. The heat sink 140 has thermal conductivity and can dissipate heat generated by the light-emitting element to the outside of the first light-emitting element substrate 100. For example, in the example shown in Figures 1 and 2, the lower surface of the first light-emitting element substrate 100, i.e., the side of the second main surface 124 of the bottom 120 of the base 110, becomes the heat dissipation surface.

In the example shown in Figure 2, the through-hole 126 of the base 110 has a cross-section perpendicular to the extension direction that has a constant size and shape. That is, the first hole 125a and the second hole 125b have the same cross-sectional shape.

However, this is just one example, and the shape of the through portion 126 is not particularly limited.

For example, the through-hole 126 of the base 110 may have two different dimensions in a cross-section perpendicular to the extension direction, with the second hole 125b having a larger cross-section than the first hole 125a.

Alternatively, the through portion 126 may have three or more different dimensions in a cross section perpendicular to the extension direction, and each cross section may increase in area from the first main surface 122 side to the second main surface 124 side.

In particular, the through portion 126 may have an inverse tapered shape in which the cross section perpendicular to the extension direction gradually increases from the first main surface 122 to the second main surface 124. Hereinafter, the shape of the through portion 126 in which the cross-sectional area increases stepwise or continuously from the first main surface 122 side to the second main surface 124 side is collectively referred to as a "flared" shape.

When the through-hole 126 has a "flared" shape, the heat dissipation characteristics of the heat sink 140 can be further improved by filling the through-hole 126 with the heat sink 140.

Here, in the first light-emitting element substrate 100, the base 110 is mainly composed of a mixed material of glass and ceramics.

On the other hand, the heat sink 140 does not substantially contain glass frit and is composed of 99% or more by mass of copper. Therefore, the heat sink 140 is not easily deteriorated by sulfurization, has low resistivity, and has good thermal conductivity.

In addition, 90% or more by volume of the glass contained in the base 110 is amorphous. Therefore, in the first light-emitting element substrate 100, the heat sink 140 is properly adhered to the base 110 even if the heat sink 140 does not contain glass frit.

As a result of the above effects, the first light-emitting element substrate 100 is less susceptible to deterioration due to sulfurization, has good adhesion to the base 110, and can provide a heat sink 140 with significantly reduced resistivity.

(Substrate for light-emitting element according to another embodiment of the present invention)
Next, a substrate for a light emitting device according to another embodiment of the present invention will be described with reference to FIG.

Figure 3 shows a schematic cross-sectional view of a substrate for a light-emitting element according to another embodiment of the present invention.

As shown in FIG. 3, a substrate for a light-emitting element according to another embodiment of the present invention (hereinafter referred to as a "second substrate for a light-emitting element") 200 has a base 210 and a heat sink 240.

The base 210 is generally rectangular in top view and has four sides, namely, the first side 212a to the fourth side 212d. Figure 3 shows the first side 212a and the third side 212c.

Also, as shown in FIG. 3, the base 210 has a side portion 215 and a bottom portion 220 located below the side portion 215.

The side portion 215 has a frame-like shape and has four portions corresponding to the first side 212a to the fourth side 212d, i.e., the first portion 215a to the fourth portion 115d. Figure 3 shows the first portion 215a and the third portion 215c.

The bottom 220 has a first main surface 222 and a second main surface 224 facing each other, and the side 215 is disposed on the first main surface 222 of the bottom 220. A light-emitting element (not shown) is disposed in a space portion surrounded by the side 215 on the first main surface 222 of the bottom 220.

The bottom 220 also has a first hole 225a having an opening on the first main surface 222 and a second hole 225b having an opening on the second main surface 224.

The heat sink 240 is filled into the first hole 225a and the second hole 225b.

In the example shown in Figure 3, the first hole 225a and the second hole 225b have different dimensions in the cross section perpendicular to the extension direction. That is, the cross section of the second hole 225b on the second main surface 224 side is larger than the cross section of the first hole 225a on the first main surface 222 side.

However, this is just one example, and the shapes of the first hole 225a and the second hole 225b and the relationship between the two are not particularly limited.

For example, the first hole 225a and the second hole 225b may have substantially equal dimensions and shapes in a cross section perpendicular to the extension direction.

However, as mentioned above, by making the size relationship between the first hole 225a and the second hole 225b into a "flared" shape as shown in Figure 3, the heat dissipation characteristics of the heat sink 140 filled in each hole 225a, 225b can be further improved.

Also, as shown in FIG. 3, the second light-emitting element substrate 200 has a first electrode 260, a second electrode 265, and a third electrode 270, which are installed at different height positions.

The first electrode 260 is disposed on the heat sink 240 on the first main surface 222 side of the bottom 220 of the base 210 so as to cover at least the heat sink 240. The second electrode 265 is disposed on the heat sink 240 on the second main surface 224 side of the bottom 220 of the base 210 so as to cover at least the heat sink 240. Furthermore, the third electrode 270 is disposed at a height position between the first electrode 260 and the second electrode 265.

The third electrode 270 separates the heat sink 240 into a first heat transfer portion 242 closer to the first main surface 222 and a second heat transfer portion 244 closer to the second main surface 224. In this case, the first heat transfer portion 242 and the second heat transfer portion 244 are electrically connected to each other via the third electrode 270.

However, the third electrode 270 may be omitted.

The first electrode 260 to the third electrode 270 are installed so as to form a desired wiring pattern between them and a light-emitting element (not shown) that will be installed later. Therefore, the form of the first electrode 260 to the third electrode 270 is not particularly limited, and the form shown in Figure 3 is merely one example.

In addition, the first electrode 260 and the second electrode 265 may be omitted during the distribution process of the second light-emitting element substrate 200. In other words, the first electrode 260 and the second electrode 265 may be installed at any time from when the light-emitting element is installed on the second light-emitting element substrate 200 until the light-emitting device is completed.

In contrast, the third electrode may be omitted in the final light-emitting device.

Here, in the second light-emitting element substrate 200, the base 210 is mainly composed of a mixed material of glass and ceramics.

On the other hand, the heat sink 240 does not substantially contain glass frit and is composed of 99% or more by mass of copper. Therefore, the heat sink 240 is not easily deteriorated by sulfurization, has low resistivity, and has good thermal conductivity.

In addition, 90% or more by volume of the glass contained in the base 210 is amorphous. Therefore, in the second light-emitting element substrate 200, the heat sink 240 is properly adhered to the base 210 even if the heat sink 240 does not contain glass frit.

As a result of the above effects, the second light-emitting element substrate 200 is less susceptible to deterioration due to sulfurization, has good adhesion to the base 210, and can provide a heat sink 240 with significantly reduced resistivity.

(Constituent members of the substrate for light-emitting element according to one embodiment of the present invention)
Next, each member included in the substrate for light emitting device according to one embodiment of the present invention will be described in more detail. Note that, here, the constituent members of the second substrate for light emitting device 200 will be described as an example.

(Base 210)
As described above, the base 210 is made of a mixed material of ceramics and glass.

Examples of ceramics that may be used include, but are not limited to, alumina, zirconia, or a mixture of both.

The glass is composed of 90% or more by volume of amorphous material. The amount of amorphous material is preferably 95% or more by volume, and more preferably 98% or more by volume, of the total glass. Most preferably, the glass is substantially entirely amorphous.

The greater the amount of amorphous material, the better adhesion can be obtained between the base 210 and the heat sink 240.

The glass preferably has a glass transition temperature Tg in the range of 550°C to 700°C. By setting the glass transition temperature Tg to 550°C or higher, the degreasing process can be properly performed during the manufacturing process of the second light-emitting element substrate 200. Furthermore, by setting the glass transition temperature Tg to 700°C or lower, the shrinkage start temperature of the base 210 is lowered, and the dimensional accuracy of the second light-emitting element substrate 200 can be improved.

The composition of the glass is not particularly limited, but is preferably, for example, a composition containing SiO ₂ , B ₂ O ₃ , CaO, and Al ₂ O _3. The glass may further contain at least one of K ₂ O and N ₂ O.

By using such a composition, the adhesion between the base 210 and the heat sink 240 is improved.

Of these, _SiO2 is a substance that serves as a network former for glass. It is preferable that _SiO2 is contained in the glass in the range of 57 mol % to 65 mol %.

If the content of SiO ₂ is less than 57 mol%, it is difficult to obtain a stable glass, and the chemical durability may be reduced. On the other hand, if the content of SiO ₂ exceeds 65 mol%, the glass melting temperature and the glass transition temperature Tg may be excessively high. The content of SiO ₂ is preferably 58 mol% or more, more preferably 59 mol% or more, and particularly preferably 60 mol% or more. In addition, the content of SiO ₂ is preferably 64 mol% or less, more preferably 63 mol% or less.

B ₂ O ₃ is a substance that serves as a network former for glass. It is preferable that B ₂ O ₃ is contained in the glass in an amount of 13 mol % to 18 mol %.

If the content of _B2O3 is less than 13 mol%, the glass melting temperature and _{the glass transition temperature Tg may be excessively high. On the other hand, if the content of B2O3 is} more than 18 _mol %, it may be difficult to obtain a stable glass and _the chemical durability may be reduced. The content of _B2O3 is preferably 14 mol% or more, more preferably 15 mol% or more. Also, the content _{of B2O3} is preferably 17 mol% or less, more preferably 16 mol% or less.

CaO is added to increase the stability and crystal precipitation of glass, as well as to lower the glass melting temperature and glass transition temperature Tg. It is preferable that CaO is contained in the glass in the range of 9 mol% to 23 mol%.

If the CaO content is less than 9 mol%, the glass melting temperature may become excessively high. On the other hand, if the CaO content exceeds 23 mol%, the glass may become unstable. The CaO content is preferably 12 mol% or more, more preferably 13 mol% or more, and particularly preferably 14 mol% or more. The CaO content is preferably 22 mol% or less, more preferably 21 mol% or less, and particularly preferably 20 mol% or less.

Al ₂ O _{3 is} added to enhance the stability, chemical durability, and strength of the glass, _and is preferably contained in the glass in an amount of 3 mol % to 8 mol %.

If the content of _Al2O3 is less than 3 mol%, _{the glass may become unstable. On the other hand, if the content of Al2O3 is} more than 8 mol%, the glass melting temperature and _the glass transition temperature _{Tg may become excessively high. The content of Al2O3 is preferably 4 mol% or more, more preferably 5 mol% or more. Also, the content of Al2O3 is preferably 7} mol% or less, more preferably 6 mol% or less.

K ₂ O and Na ₂ O lower the glass transition temperature Tg. K ₂ O and Na ₂ O are preferably contained in the glass in a total amount within the range of 0.5 mol % to 6 mol %.

If the total content of _K2O and _Na2O is less than 0.5 mol%, the glass melting temperature and the glass transition temperature Tg may be excessively high. On the other hand, if the total content of _K2O and _Na2O is more than 6 mol%, the chemical durability, especially the acid resistance, may be reduced, and the electrical insulation may also be reduced. The total content of _K2O and _Na2O is preferably 0.8 mol% or more and 5 mol% or less.

The glass composition is not limited to those consisting of only the above components, and can contain other components within a range that satisfies various characteristics such as the glass transition temperature Tg. If other components are contained, the total content is preferably 10 mol% or less.

The amount of glass contained in the base 210 is, for example, in the range of 35% by mass to 75% by mass with respect to the entire base 210. It is preferable that the amount of glass is in the range of 40% by mass to 70% by mass with respect to the entire base 210.

(Heat sink 240)
As described above, the heat sink 240 does not substantially contain glass frit, and is composed of 99% by mass or more of a sintered body of copper particles.

The particle size of the copper particles is not particularly limited, but it is preferable that the copper particles have a combination of coarse particles and fine particles. In this application, "coarse particles" means particles with a particle size of more than 1 μm, and "fine particles" means particles with a particle size of 1 μm or less.

By combining such coarse and fine particles, a dense heat sink 240 with low resistivity can be formed.

For example, the copper particles may include coarse particles having an average particle size in the range of 2 μm to 7 μm and fine particles having an average particle size in the range of 0.02 μm to 1 μm. In particular, the copper particles may include coarse particles having an average particle size in the range of 3 μm to 6 μm and fine particles having an average particle size in the range of 0.05 μm to 0.2 μm.

In addition, the volume ratio of coarse to fine copper particles (coarse:fine) may be in the range of 50:50 to 95:5, preferably in the range of 60:40 to 92:18, and more preferably in the range of 65:35 to 90:10.

The average particle size of the copper particles in the heat sink 240 can be measured by image analysis of a scanning electron microscope (SEM) image of the heat sink 240 as follows.

That is, first, the copper particles in the image are classified into coarse particles with a particle size exceeding 1 μm and fine particles with a particle size of 1 μm or less. Next, the average particle size of the coarse particles is calculated from the particle size of each classified coarse particle. Similarly, the average particle size of the fine particles is calculated from the particle size of each classified fine particle. In this way, the average particle size of the coarse and fine copper particles in the heat sink 240 is determined.

The resistivity of the heat sink 240 is preferably less than 2.8 μΩ·cm, and more preferably 2.0 μΩ·cm or less.

In addition, in the second light-emitting element substrate 200, the resistivity of the heat sink 240 can be determined by measuring the resistance between the first electrode 260 and the second electrode 265 using a four-terminal method.

Alternatively, the resistivity of the heat sink 240 may be measured using a separately prepared sample having a wiring pattern, as described below.

(First electrode 260, second electrode 265, and third electrode 270, etc.)
The first electrode 260 is made of a conductive material such as copper. For example, the first electrode 260 may be the same material as the heat sink 240.

The first electrode 260 may further have a metal plating film on the base made of a conductive material. Gold, nickel, etc. can be used as the metal plating film.

The same applies to the second electrode 265 and the third electrode 270.

(Second Light Emitting Element Substrate 200)
There is no particular limitation on the light-emitting element provided on the second light-emitting element substrate 200. The light-emitting element may be, for example, an LED or an LD.

The dimensions of the second light-emitting element substrate 200 are appropriately selected depending on the light-emitting element to be installed. The second light-emitting element substrate 200 may have, for example, a total length L shown in FIG. 1 in the range of 2 mm to 6 mm. Also, the width W shown in FIG. 1 may be in the range of 2 mm to 6 mm. Furthermore, the height H shown in FIG. 3 may be in the range of 0.5 mm to 3 mm.

(Method for manufacturing a substrate for a light-emitting element according to one embodiment of the present invention)
Next, a method for manufacturing a substrate for a light emitting device according to an embodiment of the present invention will be described with reference to FIGS.

Figure 4 shows a schematic diagram of an example of the flow of a method for manufacturing a substrate for a light-emitting element according to one embodiment of the present invention (hereinafter referred to as the "first manufacturing method"). Figures 5 to 10 also show schematic diagrams of a process for manufacturing a substrate for a light-emitting element by the first manufacturing method.

As shown in FIG. 4, the first manufacturing method includes the following steps:
(I) a step of preparing a green sheet having a through hole (step S110);
(II) filling the through holes of the green sheet with a heat sink paste (step S120);
(III) applying a conductive paste to the green sheet (step S130);
(IV) combining the green sheet with other green sheets to form an assembly (step S140);
(V) firing the assembly to form a substrate for a light-emitting device (step S150);
has.

However, step S130 is a step that is performed when necessary and may be omitted.

Each step will be described below. Note that, as an example, the manufacturing method will be described using the second light-emitting element substrate 200 shown in FIG. 3. Therefore, when referring to each component, the reference symbols shown in FIG. 3 will be used.

(Step S110)
First, a green sheet is prepared by the following method: The green sheet contains glass powder, ceramic powder, and an organic binder.

(Preparation of Glass Powder)
The glass powder can be prepared by grinding a glass having a given composition.

The glass may have, for example, the composition described above, i.e., the glass may contain _SiO2 , _B2O3 , CaO, and _Al2O3 . _The glass may further contain at least one _{of K2O} and _N2O .

The glass preferably contains, for example, 57 mol% to 65 mol% of _{SiO2 ,} 13 mol% to 18 mol% of _B2O3 , 9 mol% to 23 mol% of CaO, ₃ mol% to 8 mol% of _Al2O3 , and 0.5 mol% to 6 mol% in total of at least one selected from _K2O and _Na2O . When such glass is used as glass powder, the adhesive strength between the manufactured base 210 and the heat sink 240 can be improved.

The glass is not necessarily limited to those consisting of the above components, and can contain other components within a range that satisfies various properties such as the glass transition temperature Tg. If other components are contained, the total content is preferably 10 mol% or less.

By using glass powder of the above composition, glass with an amorphous portion of 90% or more can be obtained after the subsequent step S150.

Either dry or wet grinding methods can be used to grind glass.

In the wet grinding method, glass is ground in a solvent. Water is preferably used as the solvent. Grinding can be performed using a grinding machine such as a roll mill, ball mill, or jet mill.

The 50% average particle size (D ₅₀ ) of the glass powder obtained after the pulverization treatment is preferably 0.5 μm or more and 2 μm or less.

In the present application, the 50% average particle size (D ₅₀ ) refers to a value obtained by a particle size measuring device using a laser diffraction scattering method.

When the _D50 of the glass powder is 0.5 μm or more, the glass powder is less likely to aggregate, is easy to handle, and can be uniformly dispersed. On the other hand, when the _D50 of the glass powder is 2 μm or less, an increase in the glass softening temperature and insufficient sintering are suppressed. The particle size is adjusted by classification or the like.

(Preparation of ceramic powder)
As the ceramic powder, any ceramic powder that is commonly used in the manufacture of glass ceramics can be used, and for example, alumina powder, zirconia powder, or a mixture of alumina powder and zirconia powder can be suitably used.

The _D50 of the ceramic powder is preferably, for example, 0.5 μm or more and 4 μm or less.

(Preparation of green sheets)
Next, the above-mentioned glass powder, ceramic powder, and organic binder are mixed in a predetermined ratio to prepare a slurry for the green sheet.

Organic binders that can be used include polyvinyl butyral and/or acrylic resin.

The green sheet slurry may further contain a plasticizer, a dispersant, and/or a solvent. As the plasticizer, dibutyl phthalate, dioctyl phthalate, and/or butyl benzyl phthalate can be used. As the solvent, an organic solvent such as toluene, xylene, 2-propanol, and/or 2-butanol can be used.

In the prepared green sheet slurry, the mass ratio of glass powder to ceramic powder (glass:ceramic) is preferably in the range of 35:65 to 75:25.

The resulting green sheet slurry is formed into a sheet using a doctor blade method or similar.

The green sheet slurry is then dried to form the green sheet.

Figure 5 shows a schematic diagram of an example of a prepared green sheet (hereinafter referred to as "first green sheet 350a"). First green sheet 350a has a first main surface 352a and a second main surface 354a.

The first green sheet 350a may be constructed by stacking multiple green sheets.

Then, through holes are formed in the first green sheet 350a.

Figure 6 shows a schematic diagram of a through hole 356a formed in approximately the center of the first green sheet 350a, penetrating from the first main surface 352a to the second main surface 354a.

By repeating the above steps, multiple green sheets with through holes are produced. The dimensions of the through holes in each green sheet do not necessarily have to be the same, and the dimensions of the through holes in each green sheet may be different. The green sheets produced may also include a frame-shaped green sheet (hereinafter referred to as the "third green sheet") that constitutes the side portion 215 described above after step S150.

(Step S120)
Next, the through holes 356a of the first green sheet 350a are filled with a paste for a heat sink.

The heat sink paste is prepared by mixing copper particles and a vehicle.

Preferably, the copper particles have a combination of coarse and fine particles. For example, the copper particles may be composed of coarse particles having a _D50 in the range of 2 μm to 7 μm and fine particles having _{a D50} in the range of 0.02 μm to 1 μm. In particular, the copper particles may include coarse particles having a _D50 in the range of 3 μm to 6 μm and fine particles having _{a D50} in the range of 0.05 μm to 0.2 μm.

In addition, the volume ratio of coarse to fine copper particles (coarse:fine) may be in the range of 50:50 to 95:5, preferably in the range of 60:40 to 92:18, and more preferably in the range of 65:35 to 90:10.

The vehicle includes a resin such as acrylic and/or ethyl cellulose, and an organic solvent. The organic solvent may be, for example, alpha-terpineol.

In addition, the paste for the heat sink does not substantially contain glass frit, and therefore the heat sink formed from the paste for the heat sink after step S150 also does not substantially contain glass frit.

Next, the prepared heat sink paste is filled into the through holes 356a of the first green sheet 350a. The heat sink paste may be filled into the through holes 356a by, for example, a screen printing method.

As an example, Figure 7 shows a schematic diagram of a first green sheet 350a in which through holes 356a are filled with heat sink paste 358a.

Similarly, in the other green sheets, the through holes are filled with heat sink paste 358a.

(Step S130)
A conductive paste is then applied to first major surface 352a and/or second major surface 354a of first green sheet 350a, if desired.

The conductive paste is applied to areas of the first major surface 352a and/or the second major surface 354a where electrodes and/or wiring are required, to become electrodes and/or wiring after step S150.

For example, when forming the first electrode 260 of the second light-emitting element substrate 200, the conductive paste is placed on the first main surface 352a so as to cover the heat sink paste 358a. When forming the third electrode 270 of the second light-emitting element substrate 200, the conductive paste is placed on the second main surface 354a so as to cover the heat sink paste 358a.

The conductive paste includes conductive particles, such as metal particles, and a vehicle. The metal particles may include copper particles. In particular, the conductive paste may be the same as the heat sink paste described above.

The method of applying the conductive paste to the first green sheet 350a is not particularly limited. The conductive paste may be applied to the first main surface 352a and/or the second main surface 354a of the first green sheet 350a by, for example, a screen printing method.

Figure 8 shows, as an example, conductive pastes 359a and 361a placed at predetermined locations on the first green sheet 350a.

The conductive paste 359a is disposed on the first main surface 352a of the first green sheet 350a so as to cover the heat sink paste 358a. The conductive paste 361a is disposed on the second main surface 354a of the first green sheet 350a so as to cover the heat sink paste 358a.

Conductive paste 359a becomes the first electrode 260 after step S150, and conductive paste 361a becomes the third electrode 270 after step S150.

As mentioned above, step S130 is not a required step and may be omitted. Alternatively, step S130 may be performed at a predetermined timing after the substrate for the light-emitting element is manufactured.

However, some of the electrodes and/or conductive pastes for wiring need to be applied at this stage. For example, if a third electrode 270 is required, the conductive paste 361a that will later become the third electrode 270 needs to be placed in this process. This is because after the light-emitting element substrate is completed, the conductive paste 361a cannot be placed in the desired position.

(Step S140)
Next, the first green sheet 350a on which the heat sink paste 358a etc. is applied is combined with one or more other green sheets to form an assembly.

Figure 9 shows a schematic of two green sheets stacked together as an example.

As shown in FIG. 9, in this example, a second green sheet 350b is laminated on the underside of a first green sheet 350a.

The second green sheet 350b is prepared through the aforementioned steps S110 to S130, similar to the first green sheet 350a.

Therefore, the second green sheet 350b has a first main surface 352b and a second main surface 354b facing each other, and a through hole 356b, which is filled with heat sink paste 358b.

In addition, a third conductive paste 359b is provided on the first main surface 352b of the second green sheet 350b so as to cover the heat sink paste 358b. In addition, a fourth conductive paste 361b is provided on the second main surface 354b so as to cover the heat sink paste 358b.

The third conductive paste 359b may be omitted.

The first green sheet 350a is laminated on the second green sheet 350b such that the second main surface 354a faces or contacts the first main surface 352b of the second green sheet 350b.

Next, a third green sheet 350c is placed on top of the first green sheet 350a.

Figure 10 shows a schematic of three green sheets 350a to 350c stacked together to form an assembly.

As shown in FIG. 10, the third green sheet 350c has a first main surface 352c and a second main surface 354c facing each other, and has an approximately frame-like shape.

The third green sheet 350c is prepared through the aforementioned step S110, similar to the first green sheet 350a. However, the third green sheet 350c does not have the heat sink paste or the conductor paste applied thereto.

The third green sheet 350c is laminated on the first green sheet 350a so that the second main surface 354c faces or contacts the first main surface 352a of the first green sheet 350a and surrounds the conductive paste 359a.

This results in assembly 369.

Then, a pressure bonding process is performed on the assembly 369. This integrates the first green sheet 350a to the third green sheet 350c, and a compact is obtained.

The method of the pressure bonding process is not particularly limited. For example, the assembly 369 may be subjected to cold or hot isostatic pressing to form a molded body.

Then, in step S150, the resulting molded body is sintered. However, a degreasing step may be carried out on the molded body prior to sintering.

The degreasing process may be carried out, for example, in an inert gas atmosphere or an atmosphere containing up to 1 vol% oxygen at a temperature of 500°C or less for 1 to 10 hours.

However, the degreasing process may also be performed automatically in the next step S150, during the heating of the molded body to the sintering temperature.

(Step S150)
Next, the compact is sintered, whereby the glass powder and the ceramic powder are bonded to each other throughout the first to third green sheets 350a to 350c, thereby forming the base 210.

In addition, in the through-holes 356a of the first green sheet 350a, the copper particles in the heat sink paste 358a are bonded to each other to form the first heat transfer portion 242. In addition, in the through-holes 356b of the second green sheet 350b, the copper particles in the heat sink paste 358b are bonded to each other to form the second heat transfer portion 244.

Furthermore, electrodes and/or wiring are formed from each conductive paste. For example, the first electrode 260 is formed from the conductive paste 359a, the third electrode 270 is formed from the conductive paste 361a and the third conductive paste 359b, and the second electrode 265 is formed from the fourth conductive paste 361b.

In order to prevent oxidation of the copper particles, it is preferable that the sintering atmosphere has an oxygen concentration of 10 ppm or less. For example, it is preferable that the sintering atmosphere is an inert gas atmosphere such as a nitrogen atmosphere, or a reducing atmosphere.

If the degreasing process is carried out in an oxygen-containing atmosphere, it is preferable to carry out the firing process in a hydrogen-containing atmosphere. This allows the copper oxidized in the degreasing process to be reduced.

Considering densification and productivity, the processing temperature is preferably 850°C or higher and 950°C or lower, and more preferably 900°C or higher and 930°C or lower. The processing time is preferably 20 minutes or higher and 60 minutes or lower. When the processing temperature is 900°C or higher, a dense base body 210 and heat sink 240 are obtained. When the processing temperature is 950°C or lower, deformation of the substrate for the light-emitting element is suppressed and productivity is improved.

After the firing process, the first heat transfer portion 242 and the second heat transfer portion 244 are each bonded to the base 210.

The glass contained in the base 210 formed under the above-mentioned firing conditions is amorphous by 90% or more by volume. Therefore, the first heat transfer portion 242 and the second heat transfer portion 244 have good adhesion to the base 210 even though they do not contain glass.

Through the above steps, the second light-emitting element substrate 200 can be manufactured.

In this manner, a heat sink 240 with low resistivity can be obtained. In addition, good adhesion can be obtained between the heat sink 240 and the base 210.

Examples of the present invention will be described below. In the following description, Examples 1 to 10 are examples, and Examples 21 to 23 are comparative examples.

(Example 1)
A substrate for a light emitting element having the structure shown in FIG. 3 was manufactured by the above-mentioned first manufacturing method.

(Preparation of green sheets)
First, glass powder for a green sheet was produced by the following method.

60.4 mol % of SiO ₂ , 15.6 mol % of B ₂ O ₃ , 6 mol % of Al ₂ O ₃ , 15 mol % of CaO, 1 mol % of K ₂ O, and 2 mol % of Na ₂ O were mixed together to obtain a glass raw material.

Next, the glass raw material was placed in a platinum crucible and heated at 1600°C for 60 minutes to melt the glass raw material. The molten glass was then cooled to produce glass. The resulting glass was pulverized for 40 hours using an alumina ball mill to prepare glass powder. Ethyl alcohol was used as the solvent during pulverization.

Next, this glass powder (average particle size 1.8 μm) was mixed with alumina powder (average particle size 2.5 μm) in a mass ratio of 60:40 (glass:alumina) to produce a mixed powder of glass and alumina.

Next, 15 g of organic solvent (toluene, xylene, 2-propanol, and 2-butanol mixed in a mass ratio of 4:2:2:1), 2.5 g of plasticizer (di-2-ethylhexyl phthalate), 5 g of polyvinyl butyral, and a dispersant were added to 50 g of this mixed powder and mixed to prepare a slurry for the green sheet.

Next, this green sheet slurry was placed on a PET film using the doctor blade method. The green sheet slurry was then dried to produce a green sheet. The green sheet had a shape of approximately 3.5 mm long and 3.5 mm wide.

Next, a through hole measuring approximately 0.9 mm in length and 0.9 mm in width was formed in the green sheet, and the through hole was then filled with a heat sink paste containing copper particles.

The heat sink paste was prepared as follows:

As copper particles, a mixture of coarse particles having a _D50 of 3.8 μm and fine particles having a _D50 of 0.05 μm was prepared. The volume ratio of the coarse particles to the fine particles was 85:15.

The copper particles were mixed with ethyl cellulose in a mass ratio of 85:15, and the resulting mixture was dispersed in alpha-terpineol to a solid content of 85% by mass. The dispersion was then kneaded for 1 hour to prepare a paste for the heat sink.

The heat sink paste was filled into the through holes using screen printing.

Next, a conductive paste was applied to the green sheet at a designated location using a screen printing method. This resulted in a first green sheet. The conductive paste used was the same as the paste for the heat sink.

A second and a third green sheet were prepared in a similar manner. The three green sheets were then stacked together to form the assembly shown in Figure 10.

Next, the assembly was compressed to integrate the green sheets and form a compact. Cold isostatic pressing was used for the compression process.

Next, the obtained compact was subjected to a degreasing process. The degreasing conditions were a nitrogen atmosphere containing 1 vol% oxygen at 500°C for 5 hours. After that, the atmosphere was changed to a mixed atmosphere of 97 vol% nitrogen + 3 vol% hydrogen, and the compact was heated to 700°C for 1 hour.

After that, for the sintering process, the molded body was heated to 900°C in a nitrogen atmosphere with an oxygen content of 10 ppm or less and held there for 30 minutes.

This resulted in the production of a substrate for a light-emitting element having a base, a heat sink formed in the through hole of the base, and first to third electrodes.

By the above method, a substrate for a light-emitting element was obtained. The height of the substrate for a light-emitting element was about 1 mm.

(Examples 2 to 4)
In the same manner as in Example 1, a substrate for a light-emitting element was produced.

However, in Examples 2 to 4, the mass ratio of glass powder and alumina powder contained in the green sheet slurry was changed from that in Example 1. The other conditions were the same as in Example 1.

(Examples 5 to 10)
In the same manner as in Example 1, a substrate for a light-emitting element was produced.

However, in Examples 5 to 10, the diameters of the coarse and fine copper particles contained in the heat sink paste, as well as the mixing ratio of the two, were changed from those in Example 1. The other conditions were the same as in Example 1.

(Example 21)
In the same manner as in Example 1, a substrate for a light-emitting element was produced.

However, in this Example 21, the mass ratio of glass powder to alumina powder contained in the slurry for the green sheet was 40:60. In addition, 3 mass% of glass frit was further added to the paste for the heat sink. The other conditions were the same as in Example 1.

(Example 22)
In the same manner as in Example 21, a substrate for a light-emitting element was produced.

However, in this Example 22, the amount of glass frit added to the paste for the heat sink was 4 mass %. Also, the mixture ratio of the coarse particles and the fine particles of the copper particles contained in the paste for the heat sink was 65:35 by volume. The other conditions were the same as in Example 21.

(Example 23)
In the same manner as in Example 1, a substrate for a light-emitting element was produced.

However, in this Example 23, silver particles having a _D50 of 3.5 μm were used instead of the copper particles contained in the heat sink paste. The other conditions were the same as in Example 1.

Table 1 below summarizes the composition ratio of glass and ceramic contained in the green sheet slurry for each example, as well as the specifications of the copper particles contained in the heat sink paste.

（評価）
各例において製造された発光素子用基板などを用いて、以下の評価を実施した。

(evaluation)
The following evaluations were carried out using the light-emitting element substrates and the like produced in each example.

(Adhesion Evaluation)
The adhesion of the heat sink was evaluated as follows.

The second electrode of the light-emitting element substrate was removed to expose the heat sink on the second main surface (bottom surface).

Next, a copper wire with a diameter of 0.6 mm was soldered to the center of the heat sink. The solder area on the heat sink was about 1 mm in diameter.

In this state, the copper wire was pulled in a direction perpendicular to the second main surface of the light-emitting element substrate, and the tensile strength was measured.

As described below, different values of tensile strength were obtained for each light-emitting element substrate. From this, it is believed that the measurement method used properly evaluates the adhesion between the base and the heat sink, rather than the adhesive strength of the solder or the strength of the wire.

(Resistivity evaluation)
The resistivity was measured using a measurement sample, which was prepared as follows.

A green sheet was produced using the green sheet slurry in each of the above-mentioned Examples 1 to 10 and Examples 21 to 23. A heat sink paste was printed on the green sheet.

The printing conditions for the heat sink paste were adjusted so that the heat sink paste on the green sheet would form a wiring with a total length of 200 mm, width of 1 mm and thickness of 10 μm after firing.

After printing, the green sheet was fired at 500°C for 5 hours in a nitrogen atmosphere containing 1 vol% oxygen. The atmosphere was then changed to a mixed atmosphere of 97 vol% nitrogen + 3 vol% hydrogen, and the object to be heat-treated was heated to 700°C over 1 hour. The object to be heat-treated was then heated to 900°C in a nitrogen atmosphere with less than 10 ppm oxygen, and held there for 30 minutes before being fired.

This resulted in the creation of a measurement sample with wiring.

Using a digital multimeter, terminals were placed on both ends of the longitudinal direction of the wiring in the measurement sample, and the resistance was measured. The resistivity of the wiring was calculated from the obtained resistance value.

(Sulfuration test)
A sulfuration test was carried out using the insulating substrate with wiring used in the resistivity evaluation described above.

The sulfurization test was carried out by exposing the insulating substrate to an atmospheric environment containing 15 ppm hydrogen sulfide gas for 336 hours. The test temperature was 40°C and the relative humidity was 0%.

After the sulfurization test, the resistivity of the wiring was measured. From the results, the change (rate of change) in the resistivity of the wiring before and after the sulfurization test was evaluated.

Table 2 below summarizes the evaluation results obtained for each light-emitting device substrate or each test specimen simulating a light-emitting device substrate.

放熱体の密着性評価の結果から、例２１および例２２における発光素子用基板では、基体と放熱体との間で高い密着強度が得られることがわかった。これは、例２１および例２２において使用した放熱体には、ガラスフリットが含まれているためであると考えられる。

From the results of the adhesion evaluation of the heat sink, it was found that high adhesion strength was obtained between the base and the heat sink in the light-emitting element substrates in Examples 21 and 22. This is believed to be because the heat sinks used in Examples 21 and 22 contained glass frit.

On the other hand, the substrates for light-emitting elements used in Examples 1 to 10 also provided adhesion strength equivalent to that in Examples 21 and 22.

From this, it was found that the substrates for light-emitting elements used in Examples 1 to 10 provided good adhesion between the heat sink and the base.

Furthermore, resistivity measurements showed that the heat sinks containing the glass frit used in Examples 21 and 22 exhibited a relatively high resistivity exceeding 3.0 mΩ·cm. In contrast, the heat sinks used in Examples 1 to 10 all had a resistivity of less than 3.0 mΩ·cm, indicating that they exhibited low resistivity.

Furthermore, the rate of change in resistivity before and after the sulfurization test revealed that the heat sink used in Example 23 was prone to sulfurization. In contrast, the heat sinks used in Examples 1 to 10 showed a rate of change of less than 1%, indicating that they had good resistance to sulfurization.

This application claims priority to Japanese Patent Application No. 2019-024502, filed on February 14, 2019, the entire contents of which are incorporated herein by reference.

100 First substrate for light emitting element 110 Base 112a to 112d First side to fourth side 115 Side 115a to 115d First portion to fourth portion of side 120 Bottom 122 First main surface 124 Second main surface 125a First hole 125b Second hole 126 Through portion 140 Heat sink 200 Second substrate for light emitting element 210 Base 212a to 212d First side to fourth side 215 Side 215a to 215d First portion to fourth portion of side 220 Bottom 222 First main surface 224 Second main surface 225a First hole 225b Second hole 240 Heat sink 242 First heat transfer portion 244 Second heat transfer portion 260 First electrode 265 Second electrode 270 Third electrode 350a First green sheet 350b Second green sheet 350c Third green sheet 352a, 352b, 352c First main surface 354a, 354b, 354c Second main surface 356a, 356b Through hole 358a Heat sink paste 358b Heat sink paste 359a, 361a Conductive paste 359b Third conductive paste 361b Fourth conductive paste 369 Assembly

Claims (14)

A substrate for a light-emitting element,
a base having a first main surface and a second main surface opposed to each other, a first hole having an opening in the first main surface and a second hole having an opening in the second main surface, the first main surface being a side on which a light emitting element is provided;
a heat sink disposed in the first and second holes of the substrate, the heat sink being electrically connected from the first hole to the second hole;
having
the substrate includes a mixed material of glass and ceramics, 90 volume % or more of the glass is amorphous, the ceramics includes alumina and does not include zirconia,
The heat sink is made of 99% by mass or more of copper (except when the heat sink contains a non-oxide substance having a higher melting point than the base), the substrate for a light emitting element. The substrate for a light-emitting element according to claim 1, wherein the heat sink does not contain glass or contains up to less than 1% by mass of glass. The heat sink includes copper coarse particles and copper fine particles,
The fine particles have an average particle size in the range of 0.02 μm to 1 μm,
3. The substrate for a light-emitting element according to claim 1, wherein the coarse particles have an average particle size in the range of 2 μm to 7 μm. moreover,
a first electrode disposed on the first main surface side of the base so as to cover the heat sink;
a second electrode disposed on the second main surface side of the base so as to cover the heat sink;
The substrate for a light-emitting element according to claim 1 , comprising: The substrate for a light-emitting element according to claim 4 , wherein the first electrode is made of the same material as the heat sink, and/or the second electrode is made of the same material as the heat sink. The substrate for a light-emitting element according to claim 4 or 5, wherein the resistivity of the heat sink measured between the first electrode and the second electrode is less than 2.8 μΩ·cm. the first hole and the second hole are in communication with each other to form a through-portion,
The substrate for light emitting element according to claim 1 , wherein the heat sink is filled in the through portion. The light-emitting element substrate according to any one of claims 1 to 6, further comprising a third electrode disposed between the heat sink disposed in the first hole and the heat sink disposed in the second hole. The substrate for a light-emitting element according to any one of claims 1 to 8, wherein the base contains the glass in a range of 35% by mass to 75% by mass. The substrate is
a bottom having the first major surface and the second major surface;
a frame-shaped side portion disposed on the first main surface of the bottom portion;
The substrate for a light-emitting element according to claim 1 , comprising: A method for producing a substrate for a light-emitting element, comprising the steps of:
(I) preparing a first green sheet having a through hole,
the first green sheet includes a mixed material of glass and ceramic, the ceramic including alumina and not including zirconia;
(II) filling the through holes of the first green sheet with a heat sink paste,
the paste for heat sink contains copper particles and is substantially free of glass frit;
(III) combining the first green sheet filled with the heat sink paste with another green sheet containing the mixed material to form an assembly;
(IV) firing the assembly to form a substrate for a light-emitting device,
A substrate containing glass and ceramics is formed from the first green sheet and the other green sheets, and the glass contained in the substrate is amorphous in an amount of 90 volume % or more;
A heat sink containing 99% by mass or more of copper is formed from the heat sink paste (excluding the case where the heat sink contains a non-oxide-based substance having a higher melting point than the base) ;
The manufacturing method of the present invention. Furthermore, between the step (II) and the step (III),
The manufacturing method according to claim 11, further comprising the step of applying a conductive paste for electrodes and/or wiring to the first green sheet. The copper particles contained in the paste for heat dissipation include coarse particles and fine particles,
The granules have a _D50 in the range of 0.01 μm to 1 μm;
The method according to claim 11 or 12, wherein the coarse particles have a _D50 in the range of 2 μm to 7 μm. The manufacturing method according to any one of claims 11 to 13, wherein the mass ratio of glass to the total of glass and ceramics in the first green sheet is in the range of 35 mass% to 75 mass%.

Images