JP2001044327A - Wiring board and its mounting structure - Google Patents

Abstract

(57) [Summary] [Problem] To reduce the stress generated when a wiring board having a plurality of connection electrode layers and connection terminals arranged on the back surface of an insulating substrate is mounted on an external circuit board, and to reduce the stress generated. Maintain a stable connection for a long time. An insulating substrate, a wiring circuit layer disposed on the surface and / or inside the insulating substrate, a plurality of connection electrode layers disposed on a back surface of the insulating substrate, and In the wiring board A having the plurality of connection terminals 7 attached to the connection electrode layer 3 with the conductive adhesive 8, at least four corners z of the connection terminals 7 are made of conductive resin. Or made of a resin-containing conductor material having a Young's modulus of 30 GPa or less and lower than the Young's modulus of the connection electrode layer 3, made of a mixture of an insulating resin and a metal powder, and formed of an external circuit board such as a printed board. Mount on B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an insulating substrate made of, for example, ceramic, glass ceramic or synthetic (organic) resin, and a wiring substrate such as a semiconductor device housing package having a wiring circuit layer and connection terminals. The present invention relates to the improvement of a mounting structure in which the mounting structure is mounted on an external circuit board such as a motherboard.

[0002]

2. Description of the Related Art Conventionally, a wiring board has a structure in which a wiring circuit layer is disposed on the surface and / or inside of an insulating substrate, and as a typical example, a semiconductor element, particularly a semiconductor element such as an LSI is accommodated. A package for housing a semiconductor element is exemplified.

[0003] In the package for housing a semiconductor element, a ceramic typified by alumina, a glass ceramic, an organic resin or the like is used as an insulating layer. Especially for semiconductor element storage packages using alumina,
A wiring circuit layer of W, Mo or the like is provided on the surface and inside, and an electrode layer for connection to an external circuit board is provided on the bottom surface. Furthermore, in the center of the upper surface of the insulating substrate,
An electrode layer for connection with the semiconductor element is formed, the semiconductor element is mounted thereon, and is electrically connected to the wiring circuit layer by wire bonding or the like, and then sealed with a resin or the like. Alternatively, a cavity for mounting and housing the semiconductor element is formed at the center of the upper surface of the insulating substrate, and after mounting the semiconductor element, the cavity is hermetically sealed by brazing a lid. You.

In general, as the degree of integration of semiconductor devices increases,
Although the number of electrodes formed thereon also increases, the number of connection terminal electrodes for connecting to an external circuit board in a semiconductor storage package for storing the same also increases. However, an increase in the number of electrodes leads to an increase in the size of the package. Therefore, it is necessary to increase the formation density of the connection terminal electrodes of the package, in conjunction with the demand for downsizing the package.

[0005] In response to such market demands, a pin grid array (PGA) in which metal pins such as Kovar are connected to the lower surface of the package has been commercialized, but recently, gull wings are provided on wiring circuit layers led out on four sides of the package. -Type (L-shaped) quad flat package (QFP) with metal pins connected, electrode pads on four sides of the package, leadless chip carrier (LCC) without lead pins, flip chip mounting of Si chip And a ball grid array (BGA) in which a large number of spherical terminals made of solder are arranged on the lower surface of the insulating substrate. Of these, the BGA can achieve the highest density.

According to the ball grid array (BGA), a spherical connection terminal made of a brazing material such as solder is brazed to the connection electrode layer, and the spherical connection terminal is connected to the connection electrode layer of the external circuit board. Then, the terminal is heated and melted at about 250 to 400 ° C., or the connection terminal is connected to the connection electrode layer with a low melting point brazing material. Is mounted on an external circuit board.

[0007]

As an insulating substrate in a wiring board or a package for accommodating a semiconductor element, a ceramic or glass-ceramic wiring board has a high usefulness, a hermetic sealing property, or a multilayer technology such as a wiring circuit layer. For example, higher reliability is obtained as compared with the case where an organic resin is used.

Further, when a wiring board containing a semiconductor element is mounted on a wiring board such as a package for housing a semiconductor element on the surface of an external circuit board such as a printed board, heat generated during operation of the semiconductor element is generated between the insulating board and the printed board. The thermal expansion coefficient of the ceramic or glass ceramic insulating substrate is generally about 4 to 7 ppm.
/ ° C, whereas printed circuit boards (glass-
(Cu wiring layer formed on epoxy insulating layer) has a very large thermal expansion coefficient of 11 to 18 ppm / ° C., so that a large thermal expansion coefficient causes a large thermal stress to be generated, resulting in a wiring board or package. Cannot be stably electrically connected to a printed circuit board for a long period of time.

Particularly, in the case of a package having more than 300 terminals or a large package, the influence of the thermal stress increases. Therefore, the operation of the semiconductor element is repeatedly started and stopped, so that the outer periphery of the connection electrode layer on the lower surface of the wiring board is reduced. In particular, a large thermal stress acts on the bonding interface between the connection electrode layer on the wiring board side and the connection terminal, and as a result, the connection electrode layer is peeled off from the insulating substrate, or the connection terminal is disconnected from the connection electrode on the wiring board side. There has been a problem that the wiring board cannot be stably electrically connected to the printed board for a long period of time, such as peeling from the layer.

Further, mechanical stress, bending, deformation, etc., generated when mounting an external circuit board on which a wiring board or a semiconductor package is mounted to various electronic device bodies using screws, pins, etc. Mechanical stress,
Such as the stress caused by the impact applied when the electronic device falls, etc.
Various stresses act on the outer peripheral portion of the connection electrode layer on the lower surface of the wiring board and the bonding interface between the connection electrode layer on the wiring board and the connection terminal, and as a result, the connection electrode layer peels off from the insulating substrate, There has been a problem that the connection terminal is separated from the connection electrode layer, and the wiring board cannot be stably and electrically connected to the printed board for a long time.

Therefore, the present invention reduces the stress generated when a wiring board having a plurality of connection electrode layers and connection terminals arranged on the back surface of an insulating substrate is mounted on an external circuit board, and provides a strong and robust structure. It is an object of the present invention to provide a highly reliable wiring board capable of maintaining a stable connection state for a long time and a mounting structure thereof.

[0012]

Means for Solving the Problems The present inventors have conducted various studies in order to reduce the thermal stress generated when a wiring board such as a package for housing a semiconductor element is mounted on an external circuit board or used. As a result, by forming the connection terminals located at least at the four corners with the resin-containing conductor material, the resin-containing conductor material can absorb stress, maintain a stable connection state for a long time, and obtain high reliability. I found it.

That is, the wiring board of the present invention comprises: an insulating substrate;
A wiring circuit layer provided on the surface and / or inside of the insulating substrate, a plurality of connecting electrode layers provided on the back surface of the insulating substrate, and attached to the connecting electrode layer by a conductive adhesive; In a wiring board having a plurality of connection terminals,
At least four connection terminals among the connection terminals are formed of a resin-containing conductor material.

Further, the mounting structure of the wiring board according to the present invention comprises an insulating substrate, a wiring circuit layer disposed on the surface and / or inside the insulating substrate, and a plurality of wiring circuits disposed on the back surface of the insulating substrate. A first connection electrode layer, a wiring board including a plurality of connection terminals attached to the first connection electrode layer, an insulator, and a plurality of first electrodes disposed on the insulator surface. An external circuit board comprising: a first connection electrode layer; and a second connection electrode layer, wherein the first connection electrode layer and the second connection electrode layer are mounted on the surface of the external circuit board. In a mounting structure of a wiring board in which electrode layers are electrically connected to each other via the connection terminals, connection terminals located at at least four corners of the connection terminals are formed of a resin-containing conductor material. Is what you do.

In this configuration, the resin-containing conductor material contains a conductive resin, or is made of a mixture of an insulating resin and metal powder, has a Young's modulus of 30 GPa or less, and has a connection electrode. It is desirable that the Young's modulus of the layer is lower than that of the conductive adhesive, and that the thermal decomposition temperature of the resin in the resin-containing conductor material is higher than the melting point of the conductive adhesive.

It is preferable that the connection terminal is a ball grid array (BGA) type package made of a spherical body or a columnar body.

[0017]

FIG. 1 is a schematic cross-sectional view of a package A for storing a BGA type semiconductor device as an example of a wiring board according to the present invention, and FIG. FIG. 3 is a schematic cross-sectional view for explaining a mounting structure on a printed circuit board B using the package A of FIG. 1 as an external circuit board.

Referring to FIG. 1A, a package A for storing semiconductor elements has a wiring circuit layer 2 formed on the surface and the inside of an insulating substrate 1, and on the back surface of the insulating substrate 1, as shown in FIG. A plurality of connection terminals 7 are arranged and adhered. At the center of the upper surface of the insulating substrate 1, a semiconductor element 4 is adhered and fixed to the insulating substrate 1 via an adhesive such as glass or resin, and the semiconductor element 4 is electrically connected to the wiring circuit layer 2 by wire bonding 5, Furthermore, it is sealed by covering it with a sealing resin 6 from above. The semiconductor element 4 and the plurality of connection electrode layers 3 formed on the lower surface of the insulating substrate 1 are provided so as to be electrically connected via the wiring circuit layer 2.

As a method for mounting and sealing a semiconductor element, flip-chip mounting in which a semiconductor chip is directly mounted at the center of the upper surface of a wiring substrate using a solder bump or the like, or forming a cavity in the upper surface of the wiring substrate and forming a cavity in the cavity There is a method of airtight sealing by mounting and brazing a lid from above.

Further, according to the semiconductor element housing package A, the connection terminals 7 made of a spherical body or a columnar body are attached to the surface of the connection electrode layer 3 by the conductive adhesive 8 such as solder. .

According to the present invention, in the BGA type semiconductor element housing package A, the arrangement of the plurality of connection terminals 7 formed on the back surface of the insulating substrate 1 is shown in at least the plan view of the back surface of the package A shown in FIG. At least 4
A major feature is that the connection terminals 7 located at the corners are formed of a resin-containing conductor material.

Connection terminal 7 made of this resin-containing conductor material
Means connection terminals 7a located at four corners in FIG. 2 among a plurality of connection terminals 7 arranged as shown in FIG. 1B.
This is because, when the package A is mounted on the external circuit board B, the portions where the stress is greatest are the connection terminals 7a located at the four corners. It is desirable that the connection terminals 7b adjacent to the terminals 7a be formed of a resin-containing conductor material, and it is most desirable that all of the connection terminals 7 formed on the back surface of the insulating substrate 1 be formed of a resin-containing conductor material.

The resin-containing conductor material only needs to contain at least a resin component, and has a volume resistivity of 10%.
Desirably, it is 0 μΩ · cm or less. In particular,
1) When a conductive resin is contained as a conductive component, 2) It is composed of a mixture of a metal powder and the above-mentioned conductive resin or insulating resin.

As the resin having conductivity, a well-known resin is used, and examples thereof include a polyacetylene resin, a polyphenylene resin, and an ionic resin.

As the metal powder, Au, Ag, C
u, Al, Ni, Fe, Pd, Pt, W, Mo, Mn,
At least one or more selected from Pb, Sn, Bi, Sb and In, preferably Au, Ag, Cu, Al, N
i, at least one or more selected from Pt and Pd;
Most preferably, at least one or more metal powders or two or more alloy powders selected from Au, Ag and Cu are suitably used.

When the above-mentioned conductive resin is contained as a conductive component or when a metal powder is contained, the resin component is at least a thermosetting resin or a thermosetting resin in terms of shape retention and stability in a use environment. UV curing resin is desirable,
Examples of such a resin component include at least one selected from the group consisting of an epoxy resin, a urethane resin, an acrylic resin, a polyimide resin, a polyester resin, and a polyphenol resin.

When the resin-containing conductor material comprises the metal powder and the resin component, the content of the metal powder is 80%.
It is desirable that the content be not less than% by weight.

According to the present invention, by forming the connection terminal 7 containing such a resin component, the connection terminal 7 has a low Young's modulus characteristic due to the resin, and is generated by various factors when the external circuit board B described later is mounted. Stress can be reduced by the resin-containing conductor material.

Therefore, it is effective that the resin-containing conductor material has a Young's modulus lower than that of the connection electrode layer 3, especially a Young's modulus of 30 GPa or less and 20 GPa or less.
a, preferably 15 GPa or less, and the desired Young's modulus is obtained by appropriately selecting the metal powder and appropriately changing the mixing ratio and the curing conditions depending on the properties of the resin component used.

Further, the thermal decomposition temperature of the resin in the resin-containing conductor material is desirably higher than the melting point of the conductive adhesive used for attaching the connection terminal 7. This is because if the thermal decomposition temperature is lower than the melting point of the conductive adhesive, the resin component is decomposed and volatilized when the connection terminal 7 is attached to the connection electrode layer 3.

The connection terminal 7 is formed by forming a conductive adhesive 8 on the connection electrode layer 3, positioning the connection terminal 7 on the conductive adhesive 8, and placing the conductive adhesive 8. Is melted and heated in a reflow oven, infrared oven, VPS, or the like at a temperature at which the resin in the resin-containing conductor material does not thermally decompose, thereby melting the conductive adhesive 8 on the connection electrode layer 3 or containing the resin. The connection terminal 7 made of a conductive material can be attached.

Next, the structure when the package A having the above structure is mounted on the external circuit board B will be described. According to the mounting structure of the package A of FIG. 3 on an external circuit board B (hereinafter, referred to as a printed board B), the printed board B is attached to the surface of the insulator 10 and to the back surface of the insulating substrate 1 in the package A. A plurality of connection electrode layers 9 are formed so as to correspond to the plurality of connection terminals 7 formed, and the connection terminals on the connection electrode layer 3 formed on the back surface of the insulating substrate 1 of the package A. 7 and the connection electrode layer 9 on the surface of the printed circuit board B are connected by a conductive adhesive 11 such as solder.

In such a mounting structure, according to the present invention, the connection terminals 7 located at at least four corners are made of a resin containing via the connection terminals 7 between the connection electrode layer 3 of the package A and the connection electrode layer 9 of the printed board B. It is formed of a conductive material.

The connection portions located at least at the four corners are, as described with reference to FIG. 2, the connection terminals 7 located at the four corners.
means a. This is because package A is connected to external circuit board B
This is because, when mounted on the connection terminal, the portion where the stress becomes the largest is the connection terminal 7a located at the four corners.
It is preferable that the connection terminals 7a located at the four corners and the connection terminals 7b adjacent to the plurality of connection terminals 7a be formed of a resin-containing conductor material. Further, all the connection terminals 7a formed on the back surface of the insulating substrate 1 are formed. Is most desirably formed of a resin-containing conductor material.

In order to mount the package A for housing semiconductor elements on the printed circuit board B, the connection terminals 7 of the package A are positioned so as to contact the conductive adhesive 11 on the surface of the connection electrode layer 9 of the printed circuit board B. The conductive adhesive 11 is heated and melted by a reflow oven, an infrared oven, a VPS, or the like, and is heated and melted. The package A is mounted on the printed circuit board B by being fixed on the connection electrode layer 9.

The conductive adhesive for connecting the connection terminal 7 and the connection electrode layer 9 is made of Pb-Sn as described above.
In addition to a solder such as a system, it may be formed of the same conductive material as the resin-containing conductive material forming the connection terminals 7 at the four corners.

Thus, according to the mounting structure having the above-described structure, the thermal expansion between the insulating substrate 1 of the package A and the printed board B is caused by the rise and fall of the temperature generated when the power of the semiconductor element is turned on and off. When a thermal stress occurs due to the difference, the stress is concentrated, and the connection terminal 7 of the resin-containing conductor material having a low Young's modulus exists in a portion where cracks are easily generated. Since the connection terminals 7 alleviate the cracks, generation of cracks can be suppressed, breakage can be prevented, and the life of the connection portion can be significantly extended. As a result, long-term reliability of the mounting structure can be improved.

[0038]

Next, embodiments of the present invention will be described in detail as follows.
A hole is formed in a ceramic green sheet containing alumina as a main component, a paste containing tungsten as a main component is filled, and a connection electrode layer 3 connected to a via hole and a wiring circuit layer 2 containing a via hole are formed on the lower surface thereof. Is formed by screen printing, and the thickness of the fired substrate is 2 m.
The green sheets were pressure-laminated so as to obtain m, and a laminate was obtained. This laminate is simultaneously fired together with the wiring circuit layer 2 and the connection electrode layer 3 to produce a 35 mm square wiring board (semiconductor element storage package A), and the surface of the connection electrode layer 3 is plated with Ni-Au. gave.

The number of connection electrode layers 3 is 729,
The pitch was 1.27 mm, which was arranged in a matrix on the back surface of the wiring board A.

After that, a solder paste of 37% by weight of Pb-63% by weight of Sn is printed on the connection electrode layer 3, and the connection terminals 7 of this wiring board are coated on the surface of the electrode layer 3 at four corners, peripheral portions, and the entire surface. As shown in Table 1, the resin component contained a thermosetting epoxy resin, Ag as a metal powder, and a resin-containing conductive material whose Young's modulus was appropriately changed.
An 8 mm spherical connection terminal was placed, and heated to 230 ° C. in a reflow furnace to melt the solder and fix the spherical connection terminal.

The connection electrode layer 9 on the printed circuit board B
Similarly, a solder paste of 37% by weight of Pb and 63% by weight of Sn was printed. Thereafter, the wiring substrate A was positioned and mounted on the printed circuit board B, and then processed at 230 ° C. in a reflow furnace, and the connection terminals 7 were bonded and mounted.

The thermal expansion coefficient of the wiring board made of alumina used in this embodiment is 7 ppm / ° C., and the thermal expansion coefficient of the printed circuit board is 14 ppm / ° C.

Next, these mounting structures were alternately arranged in a constant temperature bath controlled at -40 ° C. and 125 ° C. in the air atmosphere, and both were held for 15 minutes.
A temperature cycle test was performed up to 1000 cycles. Then, the electrical resistance between the connection electrode layer 9 of the printed board B and the connection electrode layer 3 of the wiring board A was measured every 50 cycles, and the number of cycles until a change in the electrical resistance appeared is shown in Table 1.

As a comparative example, all the connection terminals 7 were made of eutectic solder of Pb 37% -Sn 63% or Pb 90%.
A printed circuit board was mounted on the surface of the printed circuit board in the same manner as described above using a spherical terminal formed with high-temperature solder of -Sn10% and subjected to the same evaluation.

[0045]

[Table 1]

As is clear from Table 1, in Sample Nos. 1 and 2 in which no resin-containing conductor material is used for the connection terminals, 250
While the resistance change occurred in the cycle or less, the durability was improved by forming the connection terminals made of the resin-containing conductor material in at least four corners according to the present invention.
In particular, by forming connection terminals made of a resin-containing conductor material at four corners and setting the resin-containing conductor material to a Young's modulus of 30 GPa or less, no resistance change is observed even when a temperature cycle test is performed up to 500 cycles. The durability can be further improved by forming the connection terminals made of the resin-containing conductor material at the four corners and the surrounding ten terminals, and further, by forming all the connection terminals with the resin-containing conductor material.

From these results, according to the configuration of the present invention,
A highly reliable wiring board mounting structure that can be accurately and firmly electrically connected to the external circuit board of the wiring board for a long period of time and that can sufficiently cope with the increase in the number of terminals due to the enlargement of semiconductor circuit elements on the wiring board. I realized it.

[0048]

As described above in detail, according to the wiring board and the mounting structure of the present invention, the connection terminal located at least at the four corners is formed of the resin-containing conductor material, so that the semiconductor element containing the semiconductor element is accommodated. It is possible to maintain a stable and stable connection state for a long period of time between a wiring board such as an element storage package and an external circuit board using glass-epoxy resin or the like as an insulator.

[Brief description of the drawings]

FIG. 1A is a schematic sectional view of a package A for housing a BGA type semiconductor element as an example of a wiring board of the present invention, and FIG.

FIG. 2 is a plan view of the back surface of the package A of FIG.

FIG. 3 is a schematic cross-sectional view for explaining a mounting structure on a printed circuit board B using the package A of FIG. 1 as an external circuit board.

[Explanation of symbols]

 A: Wiring board (package for storing semiconductor elements) B: External circuit board (printed board) 1: Insulating board 2: Wiring circuit layer 3, 9, ... Electrode layer for connection 4 ...・ Semiconductor element 7 ・ ・ ・ Connection terminal 8, 11 ・ ・ ・ Conductive adhesive

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E319 AA03 AC11 AC16 BB11 CC22 CD26 GG11 5E336 AA04 BB16 BB18 CC32 CC36 CC58 EE03 EE08 GG01 5E344 AA01 BB06 BB08 BB10 CC23 DD03 DD06 EE01

Claims (10)

[Claims] 1. An insulating substrate, a wiring circuit layer disposed on the surface and / or inside the insulating substrate, a plurality of connection electrode layers disposed on a back surface of the insulating substrate, and the connection electrode In a wiring board having a plurality of connection terminals attached to a layer by a conductive adhesive, at least four connection terminals among the connection terminals are formed of a resin-containing conductor material. . 2. The wiring board according to claim 1, wherein the resin-containing conductor material contains a conductive resin or is made of a mixture of an insulating resin and a metal powder. 3. The resin-containing conductor material has a Young's modulus of 30 G.
2. The wiring board according to claim 1, wherein the wiring board is equal to or less than Pa and lower than the Young's modulus of the connection electrode layer. 4. The wiring board according to claim 1, wherein a thermal decomposition temperature of the resin in the resin-containing conductor material is higher than a melting point of the conductive adhesive. 5. The wiring board according to claim 1, wherein said connection terminal is formed of a spherical body or a columnar body. 6. An insulating substrate, a wiring circuit layer disposed on a surface and / or inside the insulating substrate, a plurality of first connection electrode layers disposed on a back surface of the insulating substrate, A wiring board having a plurality of connection terminals attached to the first connection electrode layer, an insulator, and a plurality of second connection electrode layers provided on the insulator surface. An external circuit board, and the wiring board is placed on the surface of the external circuit board, and the first connection electrode layer and the second connection electrode layer are connected via the connection terminal. In a mounting structure of a wiring board electrically connected to each other, at least four connection terminals among the connection terminals are formed of a resin-containing conductor material. 7. The mounting structure for a wiring board according to claim 6, wherein the resin-containing conductor material contains a conductive resin or is made of a mixture of an insulating resin and a metal powder. 8. The resin-containing conductor material has a Young's modulus of 30.
7. The mounting structure of a wiring board according to claim 6, wherein GPa is equal to or less than GPa and lower than the Young's modulus of the connection electrode layer. 9. The mounting structure according to claim 6, wherein a thermal decomposition temperature of the resin in the resin-containing conductor material is higher than a melting point of the conductive adhesive. 10. The mounting structure for a wiring board according to claim 6, wherein said connection terminal is formed of a spherical body or a columnar body.