JP6487315B2 - Electronic control unit - Google Patents

Description

  The present invention relates to an electronic control device.

  In recent years, the mounting structure of an electronic control device has been increased in density due to downsizing of a substrate and an increase in the number of electronic components due to higher functionality. Accordingly, since the space for wiring the conductor on the substrate is reduced, the wiring efficiency of the substrate has been conventionally improved by pattern wiring from the substrate surface layer to the inner layer by vias that electrically connect the layers of the substrate. Yes. The vias for connecting the layers may be arranged between pads directly under the electronic components when the interval between the electronic components is narrow and difficult to arrange between the electronic components.

  In particular, when an electronic component having a heat spreader on the bottom surface is joined to the pad with solder while the via is disposed between the pads directly under the electronic component, the solder may adhere to the via hole directly under the electronic component, causing an electrical short circuit. There is.

  In order to prevent solder from adhering to the via hole, for example, the following techniques are disclosed (for example, refer to Patent Documents 1 to 3). Patent Document 1 discloses a structure of a circuit board in which a conductive member or an insulating member is filled in a via hole in advance at the time of manufacturing the substrate to prevent a short circuit failure due to solder adhesion in the via hole.

  In addition, Patent Document 2 also fills the via holes with ink for printing manufacturing information that has been used in the process of mounting electronic components on a substrate, and adhesive for temporarily fixing components, Thereafter, a circuit board mounting method is disclosed in which an electronic component is mounted to prevent a short circuit defect due to solder adhesion in the via hole.

  Furthermore, in Patent Document 3, the via opening is surrounded by a resist, and the solder application area of the heat dissipating part (heat spreader) of the electronic component is made larger than the projection range on the substrate of the heat dissipating part. A mounting structure is disclosed in which the solder flows out from a large amount of solder to a small region, thereby facilitating the escape of the solder and preventing the solder from flowing into the via.

Japanese Patent Laid-Open No. 11-17299 JP 2010-10498 JP 2013-171963 A

  However, the structure shown in Patent Document 1 has the following problems. That is, after the via hole is formed in the substrate, filling the via hole with a conductive member or an insulating member increases the cost of the substrate because another manufacturing process is added to the normal substrate manufacturing process.

  Further, the mounting method disclosed in Patent Document 2 has the following problems. That is, when filling the via hole with ink or an adhesive in the mounting process of the electronic component, it is difficult to completely fill the small-diameter via hole. In such unfilled and void locations, high thermal stress is generated in an environment where thermal stress is applied, and in the worst case, there is a possibility that the via is disconnected.

  Further, the mounting structure shown in Patent Document 3 has the following problems. In other words, the present invention is directed to a via having the same potential as the heat dissipating part (heat spreader) immediately below the heat dissipating part, and conversely for a via disposed outside the heat dissipating part having a different potential from the heat dissipating part. , Solder tends to adhere.

  An object of the present invention is to provide an electronic control device capable of preventing a solder from adhering to a via having a different potential from that of a heat spreader and an electrical short circuit.

In order to achieve the above object, the present invention provides an electronic component having a heat spreader and a terminal, a first pad facing the heat spreader, a second pad facing the terminal, and the first pad and the second pad. A substrate having a first via different in potential from the heat spreader, a solder resist having an opening on the first pad, and a solder that joins the heat spreader and the first pad, opening is arranged inside the projection region indicating the region obtained by projecting the heat spreader to the first pad, the solder is made from the first pad to the flared shape toward the heat spreader electronic In the control device, an edge of the first pad connected to the heat spreader is located below the electronic component in the projection area. The first via located outside and connected to the terminal is located outside the first pad directly below the electronic component .

  According to the present invention, it is possible to prevent solder from adhering to a via having a potential different from that of the heat spreader and causing an electrical short. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

FIG. 3 is a partial cross-sectional view after mounting an electronic component as a comparative example, and is a cross-sectional view taken along line AA of FIG. It is a figure which shows a part of pad structure of the electronic control apparatus as a comparative example (no electronic component mounting). FIG. 5 is a partial cross-sectional view showing the mounting structure of the first embodiment of the electronic control device according to the present embodiment, and is a cross-sectional view taken along the line BB of FIG. FIG. 3 is a diagram showing a part of the pad structure of the substrate of the first embodiment of the electronic control device according to the present embodiment (no electronic component mounted). It is a fragmentary sectional view which shows an example of the shape of the solder connection part of the heat spreader of an electronic component. It is a partial cross section figure which shows another example of the shape of the solder connection part of the heat spreader of an electronic component. FIG. 10 is a diagram showing a part of the pad structure of the substrate of the second embodiment of the electronic control device according to the present embodiment (no electronic component mounted). FIG. 8 is a partial cross-sectional view showing the mounting structure of the second embodiment of the electronic control device according to the present embodiment, and is a cross-sectional view along the line CC in FIG. FIG. 8 is a partial cross-sectional view showing a heat dissipation structure of a second embodiment of the electronic control device according to the present embodiment, and is a cross-sectional view taken along the line CC of FIG.

  Hereinafter, the configuration and operational effects of the electronic control 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.

(Comparative example)
First, the configuration of an electronic control device as a comparative example will be described with reference to FIGS. FIG. 1 is a partial cross-sectional view after mounting an electronic component as a comparative example, and is a cross-sectional view taken along line AA in FIG. FIG. 2 is a diagram showing a part of a pad structure of an electronic control device as a comparative example.

  On the substrate 1, there are a heat dissipating pad 100 for mounting the heat spreader 2a of the electronic component 2 and a lead pad 101 for mounting the lead terminal 2b of the electronic component 2. Vias 5 are arranged between the heat dissipation pad 100 and the lead pads 101. The vias 5 are connected to the conductor pattern 6 wired from the lead pad 101, and the conductor pattern is connected to the inner layer.

  Since the via 5 is different from the potential of the heat spreader 2a, the via 5 is disposed at a position spaced apart by a certain distance so that the solder 3a does not adhere to the via 5 and is electrically short-circuited. Thus, by arranging the vias 5 between the pads, it is possible to perform wiring using the inner layer without causing a conductor pattern to appear outside the component outer region (see FIG. 2) on the surface layer. Therefore, such a method is used when the component density is high and the component interval is narrow.

  The solder 3a of the heat spreader 2a part has a larger amount of solder than the solder 3b of the lead terminal 2b part.Therefore, the solder 3 may adhere to the hole of the via 5 at the time of component reflow after solder printing. There is a risk of short circuit. Also, the solder may be pushed out due to component displacement during component mounting or load during component mounting, and may adhere to the via during solder reflow.

  As shown in FIG. 1, the solder resist 4 is applied on the via 5 pattern so that the solder 3 is not attached, but the solder resist 4 is not applied in the via 5 hole. This is because if the inside of the hole of the via 5 is blocked with the solder resist 4, the cleaning liquid at the time of manufacturing the substrate tends to remain as a residual in the hole of the via 5, which causes migration in the substrate.

(First embodiment)
Next, a mounting structure of the electronic control device according to the first embodiment will be described with reference to FIGS.

  The substrate 1 is a printed wiring board and is a copper-clad laminate composed of four layers. The electronic component 2 is an SOP (Small Outline Package) package with a heat spreader 2a, and has eight lead terminals 2b for electrical connection with the substrate 1.

  In other words, the substrate 1 is a multilayer substrate, and the electronic component 2 has a heat spreader 2a and lead terminals 2b (terminals).

  Since the electronic component 2 is mounted on the substrate 1, the heat dissipating pad 100 is located at a position corresponding to (facing) the heat spreader 2a, and the lead pad 101 is located corresponding to (facing) the lead terminal 2b. It is joined with. On the substrate 1, a solder resist 4 for preventing solder adhesion is applied.

  In other words, as shown in FIG. 3, the substrate 1 has a heat dissipating pad 100 (first pad) facing the heat spreader 2a and a lead pad 101 (second pad) facing the lead terminal 2b (terminal). In the present embodiment, the substrate 1 is further disposed between the heat dissipating pad 100 and the lead pad 101, and further includes a via 5 (first via) having a potential different from that of the heat spreader 2a. The via 5 is a via that connects the layers of the substrate 1.

  A solder resist 4 is applied to the heat dissipating pad 100 so as to be an over resist over the entire periphery of the heat dissipating pad 100. Therefore, the solder resist opening 7 to which the solder 3 on the heat dissipation pad 100 adheres is smaller than the outer shape of the heat spreader 2a of the electronic component 2. As a result, the solder fillet after solder reflow has a shape that spreads from the substrate 1 side to the electronic component 2 side. On the other hand, the solder fillet shape of the electronic component heat dissipating portion as a comparative example in FIG. 1 is a solder fillet shape that spreads from the electronic component 2 side to the substrate 1 side.

  If the solder fillet shape has a shape that spreads from the substrate 1 side to the electronic component 2 side, the solder applied to the substrate 1 melts and spreads to the heat spreader 2a on the electronic component 2 side during solder reflow. Therefore, it is possible to prevent the solder 3 from adhering to the via 5 on the substrate 1.

  Here, the distance d of the over resist portion applied to the heat dissipating pad 100 is such that the solder resist opening 7 comes out of the heat spreader 2a region of the electronic component 2 even if the component displacement of the electronic component 2 and the dimensional tolerance of the component are taken into consideration. It is good to set so that there is no. Note that the distance d of the over resist portion applied to the heat dissipation pad 100 is a distance from the edge of the heat dissipation pad 100 to the edge of the solder resist opening 7.

  In other words, the solder resist 4 has a solder resist opening 7 (opening) on the heat dissipation pad 100 (first pad) as shown in FIG. Specifically, as shown in FIG. 4, the solder resist opening 7 is located inside a projection area (area La surrounded by the outline L) that shows an area obtained by projecting the heat spreader 2a onto the heat dissipation pad 100. Be placed. The solder 3a joins the heat spreader 2a and the heat dissipation pad 100 together. Specifically, the solder 3a has a shape that spreads from the heat dissipation pad 100 toward the heat spreader 2a.

  Usually, the heat spreader 2a has a larger connection area than the lead terminal 2b and is located in the center of the component, and therefore, external stress generated is lower than that of the lead terminal 2b. Therefore, the solder connection reliability is not a problem. Therefore, the solder fillet shape of the heat spreader 2a does not need to be a hem-spread shape that spreads like a skirt from the electronic component 2 to the substrate 1 side like the solder fillet shape of the lead terminal 2b.

  However, since the function of the heat spreader 2a is heat dissipation, the connection area of the solder 3a is important. The area of the solder resist opening 7 of the heat dissipation pad 100 depends on the heat dissipation performance of the product, but is desirably set as large as possible with respect to the area of the heat spreader 2a.

  Here, the via 5 is a through-hole formed by drilling a through-hole in the substrate 1 and plating the hole wall surface. The used via has a drill diameter of φ0.35 to 0.5 mm, a finished hole diameter after plating of φ0.3 to 0.4 mm, and a land land diameter of φ0.6 to 0.8 mm. As the hole diameter of the via 5 is smaller, the solder is less likely to adhere to the hole wall surface, but it may be determined in consideration of the current value flowing through the via.

  In addition, it is desirable that the entire outer periphery of the heat dissipating pad 100 be formed larger than the outer contour line obtained by projecting the outer shape of the heat spreader 2a on the substrate 1. This will be described with reference to FIGS. 5 and 6 are partial cross-sectional views showing an example of the shape of the solder connection portion between the heat spreader 2a of the electronic component 2 and the heat dissipating pad 100. FIG.

  As shown in FIG. 6, even if the outer shape of the heat dissipating pad 100 is smaller than the shape of the heat spreader 2a, a solder fillet having a hem-opening shape from the substrate 1 side to the electronic component 2 side is formed. However, since the via 5 can be disposed immediately below the heat spreader 2a of the electronic component 2, there is a possibility that the solder 3 adheres to the via 5 when a component shift occurs.

  Therefore, the outer shape of the heat dissipating pad 100 is made larger than the outer contour line L obtained by projecting the outer shape of the heat spreader 2a onto the substrate as shown in FIG. In other words, as shown in FIG. 4, the edge of the heat dissipating pad 100 (first pad) is located outside the projection region (region La surrounded by the outer contour line L).

  Accordingly, as shown in FIG. 5, even if the via 5 is disposed in the vicinity of the heat dissipation pad 100, the distance between the heat spreader 2a and the via 5 can be separated by a certain distance. The electronic control device manufactured in this way does not cause a short circuit because the solder adheres to the inside of the via when soldering. That is, since the distance between the via 5 and the heat spreader 2a increases, even if the electronic component 2 is displaced during solder reflow, the solder 3a between the heat spreader 2a and the heat dissipation pad 100 can be prevented from adhering to the via 5. it can.

  As described above, according to the present embodiment, it is possible to prevent the solder 3a from adhering to the via 5 having a potential different from that of the heat spreader 2a to be electrically short-circuited. Specifically, since the solder 3a wets and spreads so that the solder 3a spreads toward the heat spreader 2a from the substrate 1 when heated, the solder 3a does not come out of the heat dissipation pad 100, and the heat spreader of the electronic component 2 2a and the heat radiation pad 100 can be joined.

(Second embodiment)
A second embodiment according to this embodiment will be described with reference to FIGS. FIG. 7 is a diagram showing a part of the pad structure of the substrate of the second embodiment of the electronic control device according to the present embodiment. FIG. 8 is a partial cross-sectional view showing the mounting structure of the second embodiment of the electronic control device according to this embodiment, and is a cross-sectional view taken along the line CC of FIG. FIG. 9 is a partial cross-sectional view showing the heat dissipation structure of the second embodiment of the electronic control device according to this embodiment, and is a cross-sectional view taken along the line CC of FIG.

  The difference from the first embodiment is that the heat dissipation via 50 is arranged in the heat dissipation pad 100 immediately below the heat spreader 2a of the electronic component 2. The heat dissipation via 50 has the same GND potential as that of the heat spreader 2a of the electronic component 2.

  As shown in FIG. 7, a plurality of heat dissipation vias 50 are arranged on the heat dissipation pad 100, and as shown in FIG. 8, solder resist 4 is applied to the land portions on the heat dissipation vias 50 (in the via holes). Is not applied). Therefore, as shown in FIG. 7, the heat dissipating pad 100 includes a plurality of solder resist openings 7.

  In other words, there are two or more solder resist openings 7 (openings). The substrate 1 further includes a heat dissipation via 50 (second via) between the adjacent solder resist openings 7 having the same potential as the heat spreader 2a.

  As shown in FIG. 9, the lower surface of the heat dissipating pad 100 is in thermal contact with the metal base 8 through the heat dissipating adhesive 9, thereby forming a heat dissipating path. With this heat dissipation structure, heat generated in the component is dissipated from the heat spreader 2a to the metal base 8 through the heat dissipation via 50.

  The electronic control device manufactured in this way is excellent in heat dissipation, and solder does not adhere to the inside of the via 5 and short-circuit during soldering.

  There is a possibility that the solder 3a of the heat dissipating pad 100 adheres to the hole of the heat dissipating via 50. However, if the GND potential is the same as that of the heat spreader 2a, there is no electrical short-circuit. On the other hand, the present invention is directed to the via 5 connected to another signal line having a different potential from the heat spreader 2a.

  As described above, according to the present embodiment, it is possible to ensure heat dissipation while preventing the solder 3a from adhering to the via 5 having a potential different from that of the heat spreader 2a and being electrically short-circuited.

  The electronic control device mounting structure of the present invention can be modified in various ways without departing from the scope of the invention. For example, electronic component 2 is not only SOP, but also QFP (Quad Flat Package), QFN (Quad Flat Non Lead Package), SON (Small Outline No Lead Package), etc., with heat spreader 2a on the lower surface of the component It doesn't matter.

  In the embodiment described above, the electronic component 2 has the gull-wing-like lead terminal 2b as an example, but the shape of the terminal is not limited to this. The terminal may be a leadless terminal.

  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. Moreover, it is possible to add / delete / replace other configurations for a part of the configurations of the embodiments.

  The following aspect may be sufficient as embodiment of this invention.

  (1) An electronic component having a heat radiating portion (heat spreader 2a) and a lead portion (lead terminal 2b) on the lower surface of the component, a heat radiating pad for connecting the heat radiating portion and the lead portion with solder, and a substrate having a lead pad An electronic control device in which a via having a potential different from the potential of the heat dissipating part is disposed between the heat dissipating pad and the lead pad, wherein a solder resist opening of the heat dissipating pad is an outer shape of the heat dissipating part. The solder that joins the heat radiating part and the heat radiating pad has a shape that spreads from the substrate side toward the heat radiating part side. An electronic control device mounting structure characterized by the above.

  (2) In the mounting structure of the electronic control device according to (1), the heat dissipation pad is formed to be a certain distance larger than an outer contour line projected from the outer shape of the heat dissipation portion on the substrate. Electronic controller mounting structure.

  (3) The electronic control device mounting structure according to (2), wherein the solder resist includes at least one heat radiation pad opening.

  (4) The electronic control device mounting structure according to (3), wherein the heat dissipation pad has at least one via having the same potential as the heat dissipation portion.

1 ... Board
2… Electronic components
2a… Heat spreader
2b… Lead terminal
100 ... Heat dissipation pad
101 ... Lead pad
3 ... Solder
4 ... Solder resist
5 ... via (different potential)
6 ... Conductor pattern
7 ... Solder resist opening
8… Metal base
9… Heat dissipation adhesive
50 ... Heat dissipation via (same potential)

Claims (5)

An electronic component having a heat spreader and terminals;
A first pad facing the heat spreader, a second pad facing the terminal, and a substrate disposed between the first pad and the second pad and having a first via having a potential different from that of the heat spreader;
A solder resist having an opening on the first pad;
A solder that joins the heat spreader and the first pad;
The opening is disposed inside a projection area indicating an area obtained by projecting the heat spreader onto the first pad,
The solder is an electronic control device having a shape that spreads toward the heat spreader from the first pad ,
The edge of the first pad connected to the heat spreader is located outside the projection area directly under the electronic component,
The electronic control device according to claim 1, wherein the first via connected to the terminal is located outside the first pad immediately below the electronic component . The electronic control device according to claim 1,
The distance from the edge of the first pad to the opening is
The electronic control device according to claim 1, wherein the opening is set so that the opening does not come out of the projection area with respect to a deviation and a dimensional tolerance of the electronic component . The electronic control device according to claim 1,
The opening is
An electronic control device characterized by having two or more. The electronic control device according to claim 3,
The electronic control device further comprising a second via having the same potential as that of the heat spreader between the adjacent openings. The electronic control device according to claim 4,
The substrate is a multilayer substrate;
The first via is
Vias connecting the layers,
The second via is
An electronic control device characterized by being a heat dissipation via.

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