JPH07254781A - Mounting of electronic component - Google Patents

Abstract

PURPOSE:To provide a method of mounting an electronic component, which can solder firmly the electrodes of the electronic component to lands on a board. CONSTITUTION:Tabular solder parts 15 are respectively formed on the lower surfaces of electrodes 14 of an electronic component 11. A thermosetting bond 18 is applied in the vicinities of lands 17 on a board 16. The parts 15 are made to land on the lands 17, the lower surface of the component 11 is made to land on the bond 18 to mount the component 11 on the board 16 and the board 16 is heated. Whereupon, the bond 18 is first thermoset and a gap G between the component 11 and the board 16 is kept constant. When the board 16 is further heated and the parts 15 are made to melt, the sinking of the component 11 is stopped by the hardened bond 18. As a result, the molten parts 15 do never swell into a spherical form and are formed into solder parts 15' of a generally Japanese hand drum shaped and good form and the electrodes 14 are respectively soldered firmly to the lands 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of mounting an electronic component by soldering an electrode of the electronic component to a land of a board.

[0002]

2. Description of the Related Art As an electronic component, a bump (protruding electrode) provided on an electrode is known as a flip chip. Since such a bumped electronic component can be miniaturized, the demand for it is gradually increasing in recent years.

FIG. 6 is a front view of an electronic component with bumps mounted on a conventional substrate, and FIG. 7 is a partially enlarged sectional view of an electronic component soldered on a conventional substrate. As shown in FIG.
In the electronic component with bumps 1, the bumps 4 protruding from the electrodes 3 on the lower surface of the main body 2 are landed on the lands 6 of the substrate 5, and then the bumps 4 are heated in a heating furnace or the like to melt and then cooled. It is mounted on the substrate 5 by being solidified. When the bumps 4 are melted by heating, the electronic component 1 with bumps sinks due to its own weight and the surface tension of the solder, so that the bumps 4 bulge laterally and have a substantially spherical shape, as shown in FIG.

[0004]

Although the substrate 5 is incorporated into an electronic device, the bumped electronic component 1 self-heats when driven and naturally cools when the driving is stopped. The cooling load is repeatedly applied, and as a result, there is a problem that cracks 7 are likely to occur on the bumps 4 as shown in FIG. On the other hand, it is known that the formation of the crack 7 can be eliminated by forming the bump 4 in the shape of a thin body.

Further, as shown in FIG. 6, the bump 4 has a substantially spherical shape.
It is technically difficult to form a large number on the underside of
There is a problem that the cost tends to increase because a special bump forming device is required. Bump 4 again
Since it is difficult to control the shape and volume (quantity) of the metal, and the shape and volume, especially the height, are likely to vary, when the bumps 4 are heated and melted in a heating furnace, solder bridges occur or adhesion failure with the lands 6 occurs. There was a problem that it was easy to occur.

Therefore, the present invention solves the above-mentioned problems of the prior art and provides a mounting method of an electronic component capable of making the cross-sectional shape of a solder portion after melting and solidification into a stub shape in which cracks are less likely to occur. The first purpose. A second object is to provide a method for mounting electronic components at low cost, which is less likely to cause poor adhesion to a solder bridge or a land of a substrate.
The purpose of.

[0007]

To this end, the present invention provides a thermosetting resin in which a plate-shaped solder portion is preliminarily formed on the lower surface of an electrode of an electronic component and which is heat-cured at a temperature lower than the melting temperature of the solder portion. A bond consisting of the above is applied to the vicinity of the land at a height higher than the total thickness of the electrode, the solder and the land, the solder is aligned with the land, and the bottom surface of the electronic component is landed on the bond. By mounting the components on the board and then heating the board in a heating furnace, the bond is first thermoset, and the board is further heated to melt the solder part, and then the melted solder part is solidified to produce an electronic component. Is soldered to the substrate.
Further, a plate-shaped solder portion is formed in advance only on the lower surface of the electrode of the electronic component and the upper surface of the land of the substrate, or only the upper surface of the land of the substrate.

[0008]

According to the above construction, when the electronic component is mounted on the substrate, the bond is uncured, so that the flat surface of the plate-shaped solder portion is temporarily fixed in contact with the upper surface of the land of the substrate. Next, when the bond is heated in a heating furnace, the bond is thermally cured first, so that the electronic component is prevented from sinking due to its own weight by the cured bond, and the gap between the electronic component and the substrate is fixed at a predetermined interval. Therefore, the molten solder portion is solidified into a substantially staggered shape, and the electrode is firmly soldered to the land.

Further, the plate-shaped solder portion can be formed by plating means much more easily than the conventional spherical bump, and the thickness and volume (quantity) thereof can be easily and accurately controlled. It is possible to eliminate the occurrence of adhesion failure with the land.

[0010]

Embodiments of the present invention will now be described with reference to the drawings. 1 (a), 1 (b), 1 (c), and 1 (d) are electronic component mounting process diagrams of the first embodiment of the present invention, and FIG.
It is an enlarged view of the A section of (d). First, as shown in FIG.
A method of soldering an electronic component to a substrate will be described with reference to (b), (c) and (d). In FIG. 1A, 11 is an electronic component, which is configured by mounting a main body 12 on a sub-board 13. A large number of electrodes 14 are formed in a matrix on the lower surface of the sub-board 13.
A solder portion 15 is formed on the lower surface of the. The solder portion 15 is formed in a plate shape with a uniform thickness by plating means. Note that the electronic component 11 may not have the sub-board 13 in which the electrode 14 is directly formed on the lower surface of the main body 12.

Reference numeral 16 is a substrate, and a large number of lands (electrodes) 17 are formed in a matrix on the upper surface thereof.
The bond 18 is applied in the shape of a mountain in the vicinity of the land 17. The bond 18 is a thermosetting resin, and is thermoset at a temperature (eg, about 150 ° C.) lower than the melting temperature of the solder part 15 (generally about 183 ° C.). The bond 18 is applied by dropping it with a dispenser. Although not shown, the land 17 is coated with flux.

The electronic component 11 is mounted on the substrate 16 by an automatic mounting machine (not shown) with the electrodes 14 aligned with the lands 17 as shown in FIG. 1B. In this case, the electronic component 11 is mounted on the substrate 16 while the top of the bond 18 is crushed by the sub-board 13 so that the solder part 15 lands on the land 17 or approaches the land 17 with a slight gap.
To be installed on.

As shown in FIG. 1B, when the electronic component 11 is mounted on the substrate 16, the sub-substrate 13 is bonded to the bond 1.
The height H of the bond 18 is set to be higher than the total thickness of the electrode 14, the solder portion 15 and the land 17 so that the land 18 can be reliably landed on the top portion. If the electronic component 11 is mounted on the substrate 16 in this manner, the electronic component 11
The gap G between the substrate 16 and the substrate 16 is determined by the total thickness of the electrode 14, the solder portion 15 and the land 17. Therefore, if the thickness of the solder portion 15 is constant, all the electronic components 11
The gap G can be made equal. By adjusting the thickness and area of the solder portion 15, the gap G is sized so that the cross-sectional shape of the solder portion 15 which is heated and melted in the heating furnace becomes a substantially zigzag shape. It is possible to generate the solder part 15 ′ having a good cross-sectional shape that is substantially stepped. Here, the solder portion 15 has a simple plate shape, and can be easily formed to have a constant thickness by strictly controlling the thickness by a plating means or the like. Further, by bonding the electronic component 11 to the bond 18, the substrate 16 is conveyed by a conveyor while the substrate 16 is conveyed by a mounting process such as a heating furnace.
Even if the backlash 6 occurs, the electronic component 11 can be prevented from being displaced and the solder portion 15 from falling off the land 17.

Next, the substrate 16 is sent to a heating furnace (not shown) and heated. In the heating furnace, the substrate 16 is heated from room temperature to the melting temperature of the solder portion 15 (as described above, generally 183
The temperature is gradually heated to about 223 ° C, which is higher than the temperature (about ° C). The curing temperature of the bond 18 is about 150 ° C., which is lower than the melting temperature of the solder portion 15, and therefore the solder portion 1
The bond 18 is thermoset before the 5 melts. Figure 1
(C) shows a state in which the bond 18 is cured, and the bond 18 is thermally cured, so that the electronic component 11 and the substrate 1 are
The gap G of 6 is fixed.

When the substrate 16 is further heated in the heating furnace, the solder portion 15 is melted. When the solder portion 15 melts, the electronic component 11 tries to sink due to its own weight, but this sinking is blocked by the already cured bond 18. Therefore, the melted solder portion 15 does not bulge laterally, and if the melted solder portion 15 is subsequently cooled and solidified, the cross-sectional shape is good as shown in FIG. The solder portion 15 'is obtained. In the solder portion 15 ′ having such a thin, rugged cross section, the crack 7 as shown in FIG. 7 is extremely unlikely to occur even when the heat generation load and the cooling load accompanying the driving of the electronic component 11 are repeatedly applied. It is a thing. As described above, according to this method,
While the gap G between the electronic component 11 and the substrate 16 is kept constant, the electronic component 1 is formed by the substantially staggered solder portion 15 '.
The one electrode 14 can be firmly soldered to the land 17 of the substrate 16.

3 (a) and 3 (b) show a mounting process diagram of an electronic component when the substrate of the first embodiment of the present invention has a warp. 3A is the same step as FIG. 1B, and FIG. 3B is the same step as FIG. 1D. Figure 3
In (a), the board 16 has a warp as shown in the figure, and therefore, a part of the solder part 15 of the electronic component 11 mounted on the board 16 (in particular, the solder part 15 at the center) is attached to the land 17 of the board 16. It cannot land, and there is a slight gap Ga between the solder part 15 and the land 17.

When the solder portion 15 is melted by heating the substrate 16 in a heating furnace, the melted solder portion 15 hangs down by its own weight and becomes spherical due to surface tension to increase the thickness.
It comes into contact with the lower land 17 and is attracted to the land 17 having a good wetting property. Next, the board 16 is cooled to cool the solder part 1.
When 5 is solidified, the electrodes 14 and the lands 17 are connected by a substantially staggered solder portion 15 'as shown in FIG. 3 (b). As described above, according to this method, even if the solder portion 15 cannot land on the land 17 due to the warp of the substrate 16, if the surface of the solder portion 15 is made flat, the gap G
By absorbing a, the electrode 14 of the electronic component 11 can be firmly soldered to the land 17 of the substrate 16.

Next, a second embodiment of the present invention will be described. Figure 4
(A), (b), (c), (d) is a mounting process drawing of the electronic component of the second embodiment of the present invention. In this second embodiment,
This is different from the first embodiment in that plate-shaped solder portions 15a and 15b are formed on the lower surface of the electrode 14 and the upper surface of the land 17. The sum of the thicknesses of the two solder portions 15a and 15b is equal to the thickness of the solder portion 15 shown in FIG. This mounting method is the same as in the first embodiment, the electronic component 11 is mounted on the substrate 16 (FIG. 4B), and then the substrate 1
6 is heated in a heating furnace to thermally cure the bond 18 (see FIG.
(C)), the substrate 16 is further heated to heat the solder parts 15a,
Solder by melting and solidifying 15b (FIG. 4 (d)).

5 (a), (b), (c) and (d) are mounting process diagrams of the electronic component of the third embodiment of the present invention. In the third embodiment, the plate-shaped solder portion 15 is formed only on the upper surface of the land 17 of the substrate 16. The mounting method is the same as in the first embodiment, the electronic component 11 is mounted on the substrate 16 (FIG. 5B), and then the substrate 16 is heated to bond 1
8 is heat-cured (FIG. 5C), and the substrate 16 is further heated to melt and solidify the solder portion 15 for soldering (FIG. 5D).

[0020]

As described above, according to the present invention, by forming a plate-shaped solder portion having a predetermined thickness on the lower surface of the electrode of the electronic component and the upper surface of the land of the substrate, the electronic component and the substrate can be formed. When the solder part is heated and melted, the gap between the parts is kept constant, and while the thermosetting bond prevents the electronic parts from sinking due to their own weight, The electrodes of the electronic components can be produced and firmly soldered to the lands of the substrate. Moreover, since the plate-shaped solder portions can be formed in large quantities at low cost while accurately controlling the thickness by a plating means or the like, the mounting cost can be significantly reduced.

[Brief description of drawings]

1A is a mounting process diagram of an electronic component according to a first embodiment of the present invention, FIG. 1B is a mounting process diagram of an electronic component according to a first embodiment of the present invention, and FIG. 1C is an electronic component according to a first embodiment of the present invention. Component mounting process diagram (d) Electronic component mounting process diagram of the first embodiment of the present invention

FIG. 2 is an enlarged view of portion A of FIG. 1 (d) of the first embodiment of the present invention.

3A is a mounting process diagram of an electronic component when the substrate of the first embodiment of the present invention has a warp. FIG. 3B is a mounting process diagram of electronic component when the substrate of the first embodiment of the present invention has a warp. Process chart

4A is a mounting process diagram of an electronic component according to a second embodiment of the present invention. FIG. 4B is a mounting process diagram of an electronic component according to a second embodiment of the present invention. Component mounting process diagram (d) Electronic component mounting process diagram of the second embodiment of the present invention

5A is a mounting process drawing of an electronic component of a third embodiment of the present invention. FIG. 5B is a mounting process drawing of an electronic component of a third embodiment of the present invention. FIG. 5C is an electronic device of a third embodiment of the present invention. Component mounting process diagram (d) Electronic component mounting process diagram of the third embodiment of the present invention

FIG. 6 is a front view of a conventional electronic component with bumps mounted on a substrate.

FIG. 7 is a partially enlarged sectional view of an electronic component soldered to a conventional board.

[Explanation of symbols]

 11 electronic parts 14 electrodes 15, 15 ', 15a, 15b solder part 16 substrate 17 land 18 bond

Claims (3)

[Claims] 1. A method of mounting an electronic component, wherein an electrode formed on a lower surface of an electronic component is soldered to a land formed on an upper surface of a substrate, and a plate-shaped solder portion is previously formed on a lower surface of the electrode. In addition, a bond made of a thermosetting resin that is thermoset at a temperature lower than the melting temperature of the solder portion is provided in the vicinity of the land at a height higher than the total thickness of the electrode, the solder portion, and the land. By applying and matching the solder portion to the land, the lower surface of the electronic component is landed on the bond to mount the electronic component on the substrate, and then by heating the substrate in a heating furnace,
First, the bond is thermoset, and the solder portion is melted by further heating the substrate, and then the melted solder portion is solidified, and the electronic component is soldered to the substrate. How to mount parts. 2. The method of mounting an electronic component according to claim 1, wherein a plate-shaped solder portion is also formed in advance on the upper surface of the land of the substrate. 3. A method of mounting an electronic component, wherein an electrode formed on the lower surface of the electronic component is soldered to a land formed on the upper surface of a substrate, and a plate-shaped solder portion is previously formed on the upper surface of the land. Along with, a bond composed of a thermosetting resin that is thermoset at a temperature lower than the melting temperature of the solder portion,
The vicinity of the land is applied at a height higher than the total thickness of the electrodes, the solder portion, and the land, and the solder portion is aligned with the land, and the lower surface of the electronic component is landed on the bond. By mounting the electronic component on the substrate, then heating the substrate in a heating furnace to thermally cure the bond first, and further heat the substrate to melt the solder portion, A method of mounting an electronic component, comprising: solidifying a solder portion and soldering the electronic component to the substrate.