JP2017212266A - Electronic circuit device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic circuit device capable of improving the reliability of solder joints while maintaining wiring density.SOLUTION: A BGA package 2 includes a plurality of electrodes 21a. A substrate 3 includes a plurality of electrode pads 32a facing the plurality of electrodes 21a. A plurality of solder joints 4 electrically connect between the plurality of electrodes 21a and the plurality of electrode pads 32a, respectively. At least one wiring 32 connects adjacent electrode pads 32a to each other. At least one connecting portion 41 is joined to the wiring 32 and connects the solder joints 4 to each other on an electrode pad 32a connected by the wiring 32.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an electronic circuit device.

Due to demands for energy conservation, CO ₂ emission reduction, safety systems, etc., higher functionality for automobiles is progressing. As a result, the number of electronic circuit devices mounted on automobiles is increasing, and there is a demand for miniaturization and high functionality.

  Also, with recent improvements in automatic driving technology, a microcomputer that performs a large amount of image recognition and image processing is required. Because of these requirements, it is desired to mount a BGA package on an electronic circuit device.

  The BGA package has several hundred electrodes at the bottom of the package, and is bonded to the substrate by solder bumps formed on the electrode portions. In addition, the semiconductor contained in the BGA package generally has a high calorific value.

  For BGA packages aimed at miniaturization and high density, the problem is the extension of the life of solder joints. Currently, an in-vehicle electronic circuit device is mounted in an engine room. In addition, the self-heating causes the package temperature to rise above 125 ° C. On the other hand, it is left in an environment of minus tens of degrees Celsius, such as Alaska in winter. Since the service life and mileage of automobiles are increasing year by year, it is necessary to extend the temperature cycle life of temperature rise and low temperature cooling. Furthermore, as semiconductors become more sophisticated, BGA packages are becoming increasingly multi-pin and narrow in pitch. The area of the electrode to be soldered is also reduced, and the life of the solder joint is shortened.

  The following techniques are known for the above problems (see, for example, Patent Documents 1 to 3). In Patent Document 1, by devising the structure of the electrode pad of the BGA package and the substrate, a means for solving the bonding failure between the electrode pad and the solder and the bonding failure between the printed circuit board and the solder, and improving the reliability of the bonding portion Is provided. Patent Document 2 provides means for improving the reliability of the solder joint by devising the structure of the electrode pad of the wiring board on which the semiconductor chip is mounted. Patent Document 3 similarly provides a means for preventing a positional shift of the substrate and suppressing a decrease in reliability of the solder joint portion by devising the structure of the electrode pad of the substrate.

JP 2004-288892 A JP 2013-258347 A JP-A-2015-153816

  Extending the life of solder joints in BGA packages is a major issue. Basically, it is necessary to bring the linear expansion coefficient of the sealing resin of the BGA package close to the linear expansion coefficient of the substrate so as to reduce the load applied to the solder joint. However, when changing the linear expansion coefficient of the sealing resin, the load applied to the wiring inside the BGA package increases. Therefore, the BGA package sealing resin must be selected with an appropriate linear expansion coefficient. On the other hand, there is a means for changing the linear expansion coefficient of the substrate. Although a substrate using a base material having a small linear expansion coefficient has been developed, there is a problem of high cost because it is not widely used at present. Further, the linear expansion coefficient of the substrate changes depending on the wiring structure of the inner layer of the substrate. Although it is conceivable to construct a wiring structure of the inner layer of the board in consideration of the life of the solder joint portion, it is difficult to establish such a structure in practice.

  On the other hand, according to the techniques disclosed in Patent Documents 1 to 3, the reliability of the solder joints can be ensured.

  However, since the density of the substrate wiring around the BGA package is high, it may be difficult to dispose electrode pads as disclosed in Patent Document 1 and Patent Document 2. Further, with the technique disclosed in Patent Document 3, there is a risk of creating an area where high-density board wiring cannot be routed.

  An object of the present invention is to provide an electronic circuit device capable of improving the reliability of solder joints while maintaining the wiring density.

  In order to achieve the above object, the present invention provides an electronic component having a plurality of electrodes, a substrate having a plurality of electrode pads opposed to the plurality of electrodes, and electrically connecting the plurality of electrodes and the plurality of electrode pads, respectively. A plurality of first joints that are connected together, at least one wiring that connects adjacent electrode pads, and the first joints on the electrode pads that are bonded to the wirings and connected by the wirings And at least one second joint.

  According to the present invention, it is an object of the present invention to provide an electronic circuit device capable of improving the reliability of solder joints while maintaining the wiring density. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

1 is a schematic cross-sectional view showing an example of an electronic circuit device according to a first embodiment of the present invention. It is the schematic diagram which showed the BGA package. It is the schematic diagram which showed the example of the thermal radiation structure to the base of a BGA package. 1 is a schematic diagram showing a basic structure of a solder joint of an electronic circuit device according to a first embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a first example of solder joint connection of the electronic circuit device according to the first embodiment of the present invention, in which the solder joints are connected in a line from the solder joint at the outermost peripheral corner part. is there. FIG. 5 is a second example of solder joint connection of the electronic circuit device according to the first embodiment of the present invention, and is a schematic diagram illustrating an example in which the solder joint at the outermost peripheral corner and two adjacent solder joints are connected. FIG. FIG. 9 is a third example of solder joint connection of the electronic circuit device according to the first embodiment of the present invention, and shows an example in which the solder joint at the outermost peripheral corner and three adjacent solder joints are connected. FIG. It is an example of the solder joint part connection of the electronic circuit device by the 2nd Embodiment of this invention, and connected in the form which integrated the solder joint part of the outermost periphery corner part, and its three adjacent solder joint parts. It is the schematic diagram which showed. It is the schematic diagram which showed the example of uneven | corrugated formation for improving the wettability of a solder in the wiring which connects between electrode pads. FIG. 9B is a cross-sectional view of the wiring shown in FIG. 9A. It is the schematic diagram which showed the example of notch formation for improving the wettability of a solder in the wiring which connects between electrode pads. In 1st Embodiment, it is the figure which put together the result of the crack growth rate from the cross-sectional observation result after an endurance test with respect to a sample, when not connecting a solder joint part. In the second embodiment, when the solder joints are connected, the results of the crack growth rate are summarized from the cross-sectional observation results after the durability test for the sample when not connected.

  Hereinafter, the configuration and operational effects of the electronic circuit device according to the first and second embodiments of the present invention will be described with reference to the drawings. In each figure, the same numerals indicate the same parts.

(First embodiment)
First, the overall configuration of the electronic circuit device 1 will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing an example of an electronic circuit device 1 according to the first embodiment of the present invention.

  The electronic circuit device 1 mainly includes a cover 6, a base 7, a connector 81, and a substrate 3. The cover 6 and the base 7 constitute a housing.

  In FIG. 1, the BGA package 2, the chip component 51, and the lead component 52 are electrically connected to the substrate 3 through the solder joints 4. The connector 81 has a connector pin 82 connected to the board 3 and is fitted with an external connector. Seals 91 are sealed between the cover 6 and the connector 81, between the cover 6 and the base 7, and between the connector 81 and the base 7.

  The base 7 has a boss 71 protruding toward the BGA package 2. A surface on the front end side of the boss 71 and a surface (back surface) opposite to the surface (one main surface) of the substrate on which the BGA package 2 is mounted are bonded by a heat radiation adhesive 92.

  FIG. 2 is a schematic diagram showing the BGA package 2 before being mounted on the substrate 3. As shown in FIG. The BGA package 2 includes a package substrate 21 (interposer) on which a semiconductor chip (not shown) is mounted, a package sealing resin 22 for sealing the semiconductor chip, and a solder joint 4 (solder bump).

  FIG. 3 is a schematic diagram showing an example of a heat dissipation structure to the base 7 of the BGA package 2. As shown in FIG. Heat generated in the BGA package 2 is released into the atmosphere through the substrate 3, the heat radiation adhesive 92, the boss 71, and the base 7. FIG. 3 is a schematic diagram for explaining the heat dissipation structure of the BGA package 2. Details of the solder joint 4 will be described later with reference to FIG.

(Basic structure of solder joint)
FIG. 4 is a schematic diagram showing the basic structure of the solder joint 4 of the electronic circuit device 1 according to the first embodiment of the present invention.

  As shown in FIG. 4, the electronic circuit device 1 includes a BGA package 2 (electronic component), a substrate 3, a solder joint 4 (first joint), a wiring 32 (wiring part), and a connection part 41 (second joint). Part). The BGA package 2 has a plurality of electrodes 21a. The substrate 3 has a plurality of electrode pads 32a facing the plurality of electrodes 21a. The plurality of solder joint portions 4 (first joint portions) electrically connect the plurality of electrodes 21a and the plurality of electrode pads 32a, respectively.

  At least one wiring 32 connects adjacent electrode pads 32a. In addition, at least one connecting portion 41 (second bonding portion) is bonded to the wiring 32 and connects the solder bonding portions 4 (first bonding portions) on the electrode pads 32a connected by the wiring 32.

  In the embodiment of the present invention, the electrode of the solder joint 4 to be connected is an electrode having the same potential, such as a power supply pin or a GND pin, and even if connected, the electrode needs to have little influence on the performance of the BGA package 2 semiconductor. is there. Similarly, the signal pins other than the power supply pins and the GND pins may be connected as long as the electrodes always have the same potential.

  Further, when these electrodes are arranged at the corners of the BGA package 2, the connection of the solder joints 4 is more effective as a means for improving reliability. The connection between adjacent solder joints 4 is not limited to two solder joints 4. When all the solder joints 4 to be connected are at the same potential, a plurality of connections of three or more are more desirable.

  Examples of connecting three or more solder joints 4 are shown in FIGS. As will be described in detail later, as shown in FIG. 5, they may be connected in a line, or as shown in FIGS. 6 to 7, three and four solder joints around the corner The parts 4 may be connected so as to be integrated. Also, even if the substrate wiring is always connected with the same potential, if a long life can be sufficiently obtained by connecting some of the solder joints 4, the solder joints 4 are connected to all the electrode pads 32a. It is not necessary to connect them.

(First example)
FIG. 5 is an example of the connection of the solder joints 4 of the electronic circuit device 1 according to the first embodiment of the present invention, in which the solder joints 4 are connected in a line from the solder joints 4 at the outermost peripheral corners. It is the shown schematic diagram.

  As shown in FIG. 5, the connecting portions 41 (second joint portions) are arranged in a line. Specifically, the connecting portions 41 are arranged in a line along the diagonal line of the BGA package 2 (electronic component). The solder joints 4 on the electrode pads 32a connected by the connecting parts 41 are reinforced by the connecting parts 41 arranged in a row, and the life of the solder joints 4 is extended.

  In particular, the connecting parts 41 arranged in a row reinforce the solder joints 4 arranged at the corners of the BGA package 2 (electronic component) with the shortest life, so the reliability of the solder joints 4 of the BGA package 2 is improved. To do.

  Further, since there is no need to change the electrode pad 32a or change the layout of the wiring drawn from the electrode pad 32a, the wiring density can be maintained.

(Second example)
FIG. 6 is a second example of connection of the solder joints 4 of the electronic circuit device 1 according to the first embodiment of the present invention, and the solder joints 4 at the outermost peripheral corner part and two adjacent solder joints 4 is a schematic diagram showing an example in which 4 are connected. FIG.

  As shown in FIG. 6, the connecting portion 41 (second joint portion) includes a solder joint portion 4 (first joint portion) disposed at a corner of the BGA package 2 (electronic component) and a solder joint portion 4 adjacent thereto. Link.

  In detail, the connecting portion 41 (second joint portion) includes an arrangement of the solder joint portion 4 (first joint portion) disposed in the corner of the BGA package 2 (electronic component) and the solder joint portion 4 adjacent thereto. The solder joints 4 arranged on the outermost periphery are connected.

  The connection part 41 connected in an L shape reinforces the solder joint part 4 arranged at the corner of the BGA package 2 (electronic component) with the shortest life, thus improving the reliability of the solder joint part 4 of the BGA package 2 To do.

(Third example)
FIG. 7 is a third example of the connection of the solder joints 4 of the electronic circuit device 1 according to the first embodiment of the present invention, and the solder joints 4 at the outermost peripheral corner part and three adjacent solder joints 4 is a schematic diagram showing an example in which 4 are connected. FIG.

  As shown in FIG. 7, the connecting portion 41 (second joint portion) includes the solder joint portion 4 (first joint portion) disposed at the corner of the BGA package 2 (electronic component) and the solder joint portion 4 adjacent thereto. The solder joints 4 arranged on the outermost periphery of the arrangement are connected.

  The connecting portion 41 (second joint portion) is disposed on the diagonal line of the BGA package 2 adjacent to the solder joint portion 4 (first joint portion) disposed at the corner of the BGA package 2 (electronic component). Connect the solder joints 4 to be connected.

  Since the connecting portion 41 reinforces the solder joint portion 4 disposed at the corner of the BGA package 2 (electronic component) having the shortest life from three directions, the reliability of the solder joint portion 4 of the BGA package 2 is improved.

(Wiring connecting electrode pads)
As shown in FIG. 4, the wiring 32 connecting the electrode pads 32a on the substrate side (on the substrate 3) is exposed without supplying the solder resist 31. This is more effective when the region for supplying the solder resist 31 is made larger than the wiring 32 and not only the upper surface of the wiring 32 but also the side surfaces of the wiring 32 are exposed. The width of the wiring 32 may be smaller than the diameter of the electrode pad 32a, but is preferably as large as possible. It is more preferable if it can be made larger than the electrode pad diameter.

  Further, the surface of the wiring 32 may be subjected to a process for promoting the wettability of solder. For example, it is desirable to roughen the wiring 32, form irregularities, or form notches. Examples of wiring structures that improve wettability are shown in FIG. 9 (FIGS. 9A and 9B) and FIG.

  FIG. 9 (FIG. 9A, FIG. 9B) is a schematic diagram showing an example of forming irregularities for improving the wettability of solder in the wiring 32 connecting the electrode pads. FIG. 10 is a schematic diagram showing an example of notch formation for improving solder wettability in the wiring 32 connecting the electrode pads.

  In the example of FIG. 9 (FIGS. 9A and 9B), a plurality of ridged shapes (unevenness) are formed on the surface of the wiring 32 along the wiring direction (longitudinal direction of the wiring 32). On the other hand, in the example of FIG. 10, the wiring 32 has a notch 33 (notch) formed at the center thereof.

  As for the method of connecting the solder joints 4, the solder joints 4 may be connected when the solder bumps of the BGA package 2 are formed. Further, before bonding the BGA package 2 onto the substrate 3, solder may be supplied in advance by plating or the like onto the electrode pads 32a of the substrate 3 and the wirings 32 connecting the electrode pads 32a. When solder paste is used when the BGA package 2 is joined to the substrate 3, it is desirable to supply not only the electrode pads 32a but also the wiring 32 that connects the electrode pads 32a. This is more preferable when the amount of solder paste supplied onto the wiring 32 connecting the electrode pads 32a is larger than that on the electrode pads 32a, such as locally changing the printing mask thickness.

  Regarding the solder material, general Sn-based solder is suitable. In order to improve wettability, Sn-Ag solder may be used. When using a solder paste, the same solder material as the solder bumps of the BGA package 2 may be used, or a different solder material may be used.

The connection condition may be selected from the range from just above the melting point of the solder to be used to about 260 ° C. In order to improve the wettability, a temperature on the high temperature side is preferable. The atmosphere during connection is preferably an N ₂ atmosphere rather than the atmosphere.

(Method for manufacturing solder joints)
A method for manufacturing the solder joint portion 4 and the connecting portion 41 according to the first embodiment of the present invention will be described below. The sample used was a 416-pin BGA package. The solder joints 4 were connected to the four solder joints 4 present at the four corners of the package as shown in FIG. For the connection of the solder joints 4, the pattern was determined so as to avoid the solder resist 31 with respect to the wiring 32 connecting the electrodes of the substrate 3, and the wiring 32 was exposed.

Solder paste was supplied not only to the electrode pad 32a but also to the exposed wiring 32 and soldered by reflow. After reflow, it was confirmed that three solder joints 4 at the four corners were connected using an X-ray apparatus. Sn3Ag0.5Cu solder was used for solder bumps and solder paste. The reflow was performed using an N ₂ reflow apparatus and using a temperature profile with a peak at 250 ° C.

(An endurance test)
An endurance test was conducted on 20 samples, which were confirmed to be connected to the three solder joints 4 at the four corners, using a temperature cycle test bath. For comparison, an endurance test was also performed on a normal sample in which the solder joints 4 were not connected. The temperature conditions were -40 ° C / 125 ° C and low and high temperature holding times of 30 minutes each. After 2000 cycles, the cross-section was observed to confirm the crack growth.

  Fig. 11 shows the results of confirming the crack growth status. When the solder joints 4 were connected, it was confirmed that the crack growth rate was remarkably smaller than that of a normal sample and the life was long.

  As described above, according to this embodiment, the reliability of the solder joint can be improved while maintaining the wiring density. Specifically, according to the structure of the embodiment of the present invention, solder is spread by wetting and spreading the solder between the wiring portions between the same power supply pins and GND pins to which the board wiring is connected, and connecting the adjacent solder joints. It is possible to extend the life of the part. Thereby, it is possible to improve the solder joint reliability of the BGA package and obtain a highly reliable electronic circuit device.

(Second embodiment)
Next, another example of the solder joint portion 4 and the connecting portion 41 will be described with reference to FIG. FIG. 8 is an example of the connection of the solder joints 4 of the electronic circuit device 1 according to the second embodiment of the present invention, and the solder joints 4 at the outermost peripheral corner part and the three solder joints 4 adjacent thereto are integrated. It is the schematic diagram which showed the example connected in the form which turns into.

  In the present embodiment, the wiring 32 is formed in a region on the substrate 3 surrounded by four solder joints 4 (first joints) arranged adjacent to the corners of the BGA package 2 (electronic component). Further, the connecting portion 41 (second bonding portion) is bonded to the wiring 32 formed in the region.

  Since the connecting portion 41 reinforces the solder joint portion 4 arranged at the corner of the BGA package 2 (electronic component) having the shortest life depending on the surface, the reliability of the solder joint portion 4 of the BGA package 2 is improved.

(Method for manufacturing solder joints)
The sample used was a 416-pin BGA package 2 as in the first embodiment. The solder joints 4 were connected to the four solder joints 4 present at the four corners of the BGA package 2 as shown in FIG. For the connection of the solder joints 4, the pattern was determined so as to avoid the solder resist 31 with respect to the wiring 32 connecting the electrodes of the substrate 3, and the wiring 32 was exposed.

Solder paste was supplied not only to the electrode pad 32a but also to the exposed wiring 32 and soldered by reflow. After reflow, it was confirmed that four solder joints 4 at the four corners were connected using an X-ray apparatus. Sn3Ag0.5Cu solder was used for solder bumps and solder paste. The reflow was performed using an N ₂ reflow apparatus and using a temperature profile with a peak at 250 ° C.

(An endurance test)
An endurance test was conducted on 20 samples, which were confirmed to be connected to the four solder joints 4 at the four corners, using a temperature cycle test bath. For comparison, an endurance test was also performed on a normal sample in which the solder joints 4 were not connected. The temperature conditions were -40 ° C / 125 ° C and low and high temperature holding times of 30 minutes each. After 2000 cycles, the cross-section was observed to confirm the crack growth.

  Fig. 12 shows the results of confirming the crack growth status. When the solder joints 4 were connected, it was confirmed that the crack growth rate was smaller than that of a normal sample and the life was long. Further, comparing FIG. 11 with FIG. 12, the reliability of the solder joint 4 is more in the structure of the second embodiment shown in FIG. 8 than in the structure of the first example of the first embodiment shown in FIG. It was confirmed that it contributed to improving

  As described above, according to this embodiment, the reliability of the solder joint can be improved while maintaining the wiring density.

  In addition, this invention is not limited to above-described embodiment, Various modifications are included. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to the one having all the configurations described. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  In addition, the following aspects may be sufficient as embodiment of this invention.

  (1) In an electronic circuit device having a substrate and a BGA package bonded to one main surface of the substrate by solder, adjacent to electrode pads on the substrate corresponding to the solder bonding portion of the BGA package And a plurality of electrode pads whose electrodes are connected by substrate wiring, and solder is bonded to the electrode pads and the substrate wiring connecting the electrode pads, and the electrodes on the substrate An electronic circuit device comprising solder joints joined to pads.

  (2) In the electronic circuit device of (1), some of the electrode pads and the electrode pads are connected among the plurality of electrode pads adjacent to each other and connected between the electrodes by the substrate wiring. An electronic circuit device, wherein solder is joined on a substrate wiring, and solder joints joined to the part of the electrode pads are connected to each other.

  (3) The electronic circuit device according to (1) and (2), wherein the connected solder joints are arranged in a line.

  In the BGA package, the power supply pins and GND pins are distributed to multiple electrode pads. These electrode pads are wired so as to connect the electrode pads on the substrate side in order to suppress problems such as noise and EMC. Even in this case, the electrode pads of the substrate are formed so as to correspond to the solder bumps formed on the electrode pads of the BGA. In the embodiment of the present invention, by exposing the wiring part connecting the electrodes, the solder bumps of the BGA package and the solder paste supplied at the time of soldering are wetted and spread, and the adjacent soldered parts are connected. Realizes longer life. Thereby, it is possible to dramatically extend the life of the solder joint.

In the automobile, energy saving, CO ₂ emission reduction, and higher functions such as safety systems are expected to continue. In-vehicle electronic circuit devices are indispensable for controlling these functions, and it is thought that the added value will continue to increase in the future. Against such a background, the present invention capable of improving the reliability of an electronic circuit device is very useful and is considered to be effective for all electronic circuit devices mounted with a BGA package.

1 ... Electronic circuit device
2 ... BGA package
21 ... Package substrate
22 ... Package sealing resin
23… BGA package corner
3 ... Board
31 ... Solder resist
32 ... Wiring that connects electrode pads and electrode pads
33 ... Notch
4… Solder joint
41. Solder joint and connecting part with adjacent solder joint
51… Chip parts
52… Lead parts
6 ... Cover
7… Base
71 ... Boss
81 ... Connector
82 ... Connector pin
91… Seal material
92 ... Heat dissipation adhesive

Claims (10)

An electronic component having a plurality of electrodes;
A substrate having a plurality of electrode pads facing the plurality of electrodes;
A plurality of first joints that electrically connect the plurality of electrodes and the plurality of electrode pads, respectively;
At least one wiring connecting adjacent electrode pads;
At least one second joint that joins to the wiring and connects the first joints on the electrode pads connected by the wiring;
An electronic circuit device comprising: The electronic circuit device according to claim 1,
The second joint is
An electronic circuit device characterized by being arranged in a line. The electronic circuit device according to claim 2,
The second joint is
The electronic circuit device is arranged in a line along a diagonal line of the electronic component. The electronic circuit device according to claim 1,
The second joint is
An electronic circuit device comprising: connecting the first joint disposed in a corner of the electronic component and the first joint adjacent thereto. The electronic circuit device according to claim 1,
The second joint is
The electronic circuit device, wherein the first joint disposed at a corner of the electronic component and the first joint disposed adjacent to the first joint and disposed at the outermost periphery of the arrangement of the first joint are connected. The electronic circuit device according to claim 5,
The second joint is
The electronic circuit device, wherein the first joint disposed at a corner of the electronic component is connected to the first joint disposed adjacent to the diagonal of the electronic component. The electronic circuit device according to claim 4,
The wiring is
Formed in a region on the substrate surrounded by the four first joints disposed adjacent to the corners of the electronic component;
The second joint is
An electronic circuit device, wherein the electronic circuit device is bonded to the wiring formed in the region. The electronic circuit device according to claim 1,
On the surface of the wiring,
An electronic circuit device characterized in that irregularities are formed. The electronic circuit device according to claim 1,
The wiring is
An electronic circuit device comprising a notch. The electronic circuit device according to claim 1,
The wiring is
An electronic circuit device characterized by being exposed.

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