JP2009147014A - Resin sealed type electronic control unit and sealing molding method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin sealed type electronic control unit which can have a long lifetime and obtain high reliability by enhancing durability against thermal stress while suppressing an increase in manufacturing cost as much as possible. <P>SOLUTION: The resin sealed type electronic control unit includes a wiring board 2 having at least two wiring layers 2a and many through-holes 3 penetrating the wiring layers 2a and 2a along their thicknesses to electrically connect them to each other and also each having an inner peripheral surface formed of a conductor pattern 3a, an electronic component 2 mounted on the wiring board 2, a metallic base mounted with the wiring board 2, and a connector fitted to the metallic base to electrically connect the wiring board 2 to the outside, wherein the entire surface of the wiring board 2 and a portion of the metallic base are sealed and molded in one body with a thermosetting resin 10 and the through-holes 3 are filled with the thermosetting resin 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a resin-sealed electronic control device in which the entire surface of a printed wiring board and a part of a metal base are integrally sealed with a thermosetting resin, and a sealing molding method thereof. The present invention relates to a resin-sealed electronic control device suitable for an in-vehicle engine control unit and the like used in a rough environment and a sealing molding method thereof.

  In-vehicle electronic control devices such as engine control units (hereinafter referred to as ECUs) are required not only to have higher functionality but also to lower costs. In addition, the mounting position of the ECU is required from the passenger compartment to the engine room and directly to the engine, and the environmental temperature becomes severe and high reliability is also required. In recent years, there is a new exhaust gas regulation in the field of general-purpose diesel engines, and in order to clear this regulation, the flow of mechanical control from mechanical type is progressing.

  ECUs for general-purpose diesel engines have a wide range of uses such as agricultural machinery, industrial machinery, ships, etc., and their mounting positions are not covered with bonnets like automobiles, but are placed in an environment exposed to the atmosphere. In some cases, it is often used in harsher environments than automotive ECUs. Therefore, the ECU for general-purpose diesel engines needs higher reliability than the ECU for automobiles.

  Conventionally, typical in-vehicle ECUs include low-priced ECUs that have a semiconductor package mounted on a printed wiring board, but they are inferior in reliability.

  On the other hand, there are high heat resistance and high reliability ECUs in which bare chips are mounted on a ceramic substrate typified by on-engine ECUs, but they are expensive.

  As one of the measures to increase the reliability of the electronic control unit based on the conventional low-priced ECU, for example, in Patent Document 1 below, the resin sealing technology established in the semiconductor field is applied to the ECU. Has been proposed.

  In addition, as can be seen in the following Patent Document 2 and the like, in the semiconductor industry, it is already common to use a thermosetting resin (composition) for a package of a semiconductor chip and perform sealing molding by a transfer mold method. Established as a technology.

  Further, in Patent Document 3 below, in a wiring board having a plurality of wiring layers, an inner peripheral surface penetrating in the thickness direction thereof is formed with a conductor pattern so as to electrically connect the wiring layers to each other. It is disclosed to provide a through hole.

JP 2006-190725 A JP 2005-56944 A JP 2006-140365 A

  A wiring board provided with a through hole for electrically connecting a plurality of wiring layers to each other (in addition, for heat dissipation) as described in Patent Document 3 seems to be repeatedly subjected to thermal fatigue. Under such an environment, a large thermal stress is applied to the inside of the through hole, and the conductor pattern covering the inner surface of the through hole may be disconnected. In particular, an FR4 printed wiring board having a large coefficient of linear expansion is likely to generate a large stress concentration, and is inexpensive but has low reliability.

  In order to reduce the stress concentration due to the difference in coefficient of linear expansion as much as possible, it is necessary to use a ceramic substrate with high heat resistance and low thermal expansion instead of an inexpensive resin printed wiring board, which is costly. was there.

  The present invention has been made to solve the above-mentioned problems, and its purpose is to increase the durability against thermal stress and extend the life while suppressing the increase in manufacturing cost as much as possible. It is another object of the present invention to provide a resin-sealed electronic control device and a sealing molding method thereof that can achieve high reliability.

  In order to achieve the above object, the resin-sealed electronic control device according to the present invention has at least two wiring layers and penetrates in the thickness direction so as to electrically connect the wiring layers to each other. A wiring board provided with a number of through-holes each having a conductive pattern on the peripheral surface, an electronic component mounted on the wiring board, a metal base on which the wiring board is mounted, and the wiring board attached to the metal base And a connector for electrically connecting the outside and the outside, and the entire surface of the wiring board and a part of the metal base are integrally sealed with a thermosetting resin, and the inside of the through hole The thermosetting resin is filled.

  By doing so, the durability of the through-hole (conductor pattern) against thermal stress is enhanced, so that the life of the device can be extended and high reliability can be obtained. This technology is useful for in-vehicle engine control units and the like that require high reliability despite being used in harsh environments.

Also, one of the sealing molding methods according to the present invention is a method used for sealing molding of the resin-sealed electronic control device, wherein a sub-module including the wiring board, the metal base, and the connector is made of gold. Set in a mold, and inject and fill the thermosetting resin into the mold, t <2P × d / 3 (where d is the hole diameter (mm) of the through hole, t is the plate of the wiring board) It is characterized by sealing molding with a molding pressure P (kgf / cm ² ) that satisfies the thickness (mm).

Here, the molding pressure P is a pressure applied to the entire resin during resin sealing molding, and is a pressure with respect to atmospheric pressure. The molding pressure P is in the range of 5 to 120 kgf / cm ² , but it is desirable that the molding pressure be as high as possible in order to eliminate voids. This is because, for example, the void volume can be reduced to 1/10 at a molding pressure of 10 kgf / cm ² .

FIG. 5 is a graph in which the above formula (1) is specifically plotted when the molding pressure is 10 kgf / cm ² . In the resin-sealed electronic control device according to the present invention, the relationship between the thickness t of the wiring board and the hole diameter d of the through hole is set so as to be within the range of the hatched portion X in FIG.

  Here, there may be a plurality of through holes having different hole diameters d within the range of t <2P × d / 3 (1) in the above formula. By adjusting the molding pressure P so as to satisfy the above formula (1) during sealing molding using the transfer mold (transfer molding) method or compression molding (compression molding) method, the molten resin is put into the through hole. In other words, the required hole filling and filling can be ensured, so that the durability of the through-hole (conductor pattern) against thermal stress is improved, and the life of the device is extended. It is possible to achieve high reliability.

  Further, another one of the sealing molding methods according to the present invention is a method used for sealing molding of the resin-sealed electronic control device, and includes a sub-module including the wiring board, the metal base, and the connector. Set in a mold, inject the thermosetting resin into the mold from one side of the wiring board, fill the one side, and then flow to the other side It is characterized by making it overflow from this other surface side.

  In this case, preferably, a dummy cavity is provided in the mold, and the gate portion of the mold and the dummy cavity are interposed through a gap formed between the metal base and one surface of the wiring board. In order to prevent communication, the metal base is provided with a partition projection that reaches one surface of the wiring board.

  By doing so, at the time of sealing molding by the transfer mold method or the compression mold method, the joining point of the molten resin that is injected into the mold and flows cannot be formed inside the molded product, and the weld void or the entrained void This makes it possible to improve the product yield and to prevent the molten resin from joining the inside of the through-hole. It is possible to achieve high reliability.

  Further, another one of the sealing molding methods according to the present invention is a method used for sealing molding of the resin-sealed electronic control device, and a submodule including the wiring board, the metal base, and the connector is provided. When performing sealing molding by setting in a mold and injecting and filling the thermosetting resin into the mold, the inside of the mold is depressurized below atmospheric pressure.

  By doing so, it is possible to suppress the occurrence of defects such as air entrainment and voids at the time of sealing molding by the transfer mold method or the compression mold method, and it becomes possible to improve the product yield. .

  Since the resin-sealed electronic control device according to the present invention is filled with a thermosetting resin for sealing in the through-hole, the durability of the through-hole (conductor pattern) against thermal stress is enhanced, The lifetime of the apparatus can be extended and high reliability can be obtained.

  Moreover, according to the sealing molding method of the resin-sealed electronic control device according to the present invention, the yield of the product can be improved and the durability of the through hole (the conductor pattern) against the thermal stress can be improved. Thus, the lifetime of the apparatus can be extended and high reliability can be obtained.

  Hereinafter, embodiments of the resin-sealed electronic control device of the present invention will be described with reference to the drawings.

  FIG. 1 is a bird's-eye view showing an appearance of an embodiment of a resin-sealed electronic control device according to the present invention, FIG. 2 is a partially cut-away bird's-eye view of the resin-sealed electronic control device shown in FIG. It is a longitudinal cross-sectional view of the resin-sealed electronic control device shown in FIG.

  The resin-sealed electronic control device 1 of this embodiment is used as, for example, an in-vehicle engine control unit (ECU), and has an FR4 having four wiring layers 2a, 2a,... As shown in FIG. Printed wiring board 2 (size is 103 × 90 × 1.6 mm), electronic components 6a, 6b (microcomputers) and 6c mounted on this wiring board 2, metal base 4 on which wiring board 2 is mounted, A connector 5 is provided that is attached to the metal base 4 and electrically connects the wiring board 2 and the outside. The entire surface of the wiring board 2 and a part (inner surface) of the metal base 4 are thermosetting resin 10. Are integrally formed by sealing.

  The wiring board 2 is mounted and held in a state of being slightly lifted from the bottom surface of the metal base 4. Further, the wiring board 2 has through-holes 3 (see FIG. 4) whose inner peripheral surface is formed of a conductor pattern 3a that penetrates the wiring layers 2a, 2a,. ) Are provided, and the sealing thermosetting resin 10 is filled in the through-holes 3. The through-hole 3 is a through-hole having a hole diameter d of 1 mm or less (as described later, 0.4 mm and 0.6 mm are prepared as examples), and are indicated by dots in FIG. ), The electronic components 6a, 6b, 6c,... That generate a large amount of heat are arranged at close intervals (densely) (for heat dissipation).

  The wiring board 2 has a linear expansion coefficient in the thickness direction of 20 to 70 ppm / ° C., an elastic modulus of 20 to 35 Gpa, a glass transition temperature of 120 to 175 ° C., and the material is an epoxy resin, polyimide resin, or bismaleimide. Either a resin printed board in which glass fiber or inorganic filler is blended with a triazine resin, or a flexible board made of polyimide or a liquid crystal polymer can be used. On the surface layer of the wiring board 2, electronic components 6a and 6c such as FET, IC, diode, crystal, ceramic capacitor, chip resistor, microcomputer 6b, etc. are Sn / Pb eutectic solder, Sn / Ag / Cu lead It is mounted using free solder.

  The metal base 4 on which the printed wiring board 2 is mounted serves as a heat sink, an electromagnetic shield, a bracket attached to a vehicle or the like, which becomes a heat radiation path for heat generated by the electronic components 6a, 6b, 6c and the like. The adhesion strength between the wiring board 2 and the thermosetting resin (composition) 10 is not so high, and the surface of the wiring board 2 is contaminated by the flux during soldering. As described above, the metal base 4 It is desirable that a support portion 4b for floating and supporting the wiring board 2 is provided on the bottom surface of the wiring board 2 and the entire surface of the wiring board 2 and the inner surface of the metal base 4 are integrally resin-sealed. Thereby, a highly adhesive structure can be obtained. Moreover, the support part 4b becomes an electrical contact between the metal base 4 and the printed wiring board 2, and can lead to a ground necessary for improving the EMC resistance.

  At this time, a high adhesion structure can be obtained by setting the surface roughness of the adhesion surface with the resin to 2 to 25 μm by physical blasting or chemical etching as necessary. As a material for the metal base 4, aluminum, iron, copper, and alloys thereof are generally used.

  The connector 5 is provided with a required number of metal terminals 5a for electrically connecting the wiring board 2 and the outside. The housing portion 5b is attached to the metal base 4 and Are not touching. This is to avoid the occurrence of thermal stress due to the difference in linear expansion coefficient between the housing part 5b and the wiring board 2, or the difference in linear expansion coefficient between the housing part 5b and the thermosetting resin 10. Therefore, polyphenylene sulfide (PPS), polybutylene terephthalate (PBT), nylon (PA66), etc. having a large linear expansion coefficient can be used as the material of the housing portion 5b.

  Next, an example of a sealing molding method for the resin-sealed electronic control device 1 having the above-described configuration will be described.

In this example, resin sealing molding is performed by a transfer mold method. First, the submodule 7 including the wiring board 2, the metal base 4, and the connector 5 is set in a mold at 175 ° C. The mold is filled with a thermosetting resin (composition) 10 having physical properties of a linear expansion coefficient of 16 ppm / ° C., an elastic modulus of 15 Gpa, and a glass transition temperature of 125 ° C., and a molding pressure that satisfies the following formula (1) Sealing is performed for 3 minutes with P (kgf / cm ² ).

  However, in the following formula (1), the hole diameter of the through hole 3 is d (mm), and the plate thickness of the wiring board 2 is t (mm).

        t <2P × d / 3 ……… (1)

Specifically, as shown in [Table 1] below,
Example 1 The thickness t of the substrate 2 is 1.6 mm, and the hole diameter d of the through hole 3 is 0.4 mm.
Molding pressure P is 10 (kgf / cm ² )
Example 2 ... The thickness t of the substrate 2 is 1.6 mm, and the hole diameter d of the through hole 3 is 0.6 mm.
Molding pressure P is 10 (kgf / cm ² )
Example 3 ... The thickness t of the substrate 2 is 1.6 mm, and the hole diameter d of the through hole 3 is 0.6 mm.
Molding pressure P is 30 (kgf / cm ² )
It was.

Moreover, in order to verify the effect of this invention, the following comparative examples 1 and 2 were prepared.
Comparative Example 1 ... without resin sealing molding (no resin sealing)
The thickness t of the substrate 2 is 1.6 mm, and the hole diameter d of the through hole 3 is 0.4 mm.
No molding pressure P applied Comparative Example 2 ... Resin-sealed molding was performed in the same manner as in Examples 1, 2, and 3 (with resin sealing)
The thickness t of the substrate 2 is 1.6 mm, and the hole diameter d of the through hole 3 is 0.4 mm.
Molding pressure P is 5 (kgf / cm ² )

  As a material of the thermosetting resin (composition) 10, an epoxy composite material (thermosetting resin) that contains an inorganic filler and is solid at 40 ° C. or lower is used. As the inorganic filler, it is possible to use at least one kind of spherical shape or square shape such as fused silica, crystalline silica, alumina, magnesium oxide, boron nitride, silicon nitride, silicon carbide and the like.

  In addition, the thermosetting resin (composition) 10 has physical properties after curing having a linear expansion coefficient of 5 to 25 ppm / ° C., an elastic modulus of 8 to 30 Gpa, and a glass transition temperature of 80 to 200 ° C.

  Resin sealing molding was performed as described above to obtain a resin-sealed electronic control device 1 as shown in FIGS.

  The resin-encapsulated electronic control device 1 thus obtained was subjected to a thermal shock test under the conditions of −40 ° C. to 130 ° C. (ΔT = 170 ° C.) for 1 hour, and is shown in [Table 1]. As described above, the failure mode of Comparative Examples 1 and 2 is through-hole disconnection, and the failure mode of Examples 1, 2, and 3 is breakage of electronic component parts.

  As is clear from the test results of Comparative Example 1 and Comparative Example 2, the single-use FR4 printed circuit board without resin sealing in Comparative Example 1 has a substrate life of 700 cycles (cyc), whereas in Comparative Example 2, through hole 3 It was found that voids were generated in the internal thermosetting resin 10, resulting in a substrate life of only 500 cycles.

  On the other hand, in Examples 1, 2, and 3, all had a substrate life of 1500 cycles or more, and the thermosetting resin 10 inside the through hole 3 had no voids.

  The results are summarized as follows. When the entire surface of the FR4 printed circuit board 2 is sealed with a thermosetting resin 10 and the same thermosetting resin 10 is filled in the through hole 3, a void is formed in the thermosetting resin 10 in the through hole 3. Case (Comparative Example 2), a case where there is no thermosetting resin 10 in the through hole 3 (Comparative Example 1), a case where the inside of the through hole 3 is completely filled with the thermosetting resin 10 (Example 1) The durability (substrate life) and reliability increase in the order of 2, 3).

  As described above, since the resin-sealed electronic control device 1 of the present embodiment is filled with the thermosetting resin 10 for sealing in the through-hole 3, the through-hole 3 (conductor pattern of the through-hole 3 with respect to thermal stress) The durability and the like of 3a) are improved, and the lifetime of the apparatus can be extended, and high reliability can be obtained.

  Next, another example of the sealing molding method according to the present invention will be described.

  Also in this example, the above-described electronic control device 1 is subjected to resin sealing molding by a transfer mold method. First, as shown in FIG. 6, the electronic control device 1 includes the wiring substrate 2, the metal base 4, and the connector 5. The submodule 7 is set in a mold 8 heated to 150 ° C. to 180 ° C., and a thermosetting resin tablet 12 that is solid at room temperature is melted and injected from the gate portion 9 of the mold 8.

  Here, a dummy cavity 11 is provided in the mold 8, and the gate portion 9 of the mold 8 and the dummy cavity 11 are interposed through a gap S formed between the bottom surface of the metal base 4 and the lower surface of the wiring board 2. The metal base 4 is provided with a partition projection 4a having a concave cross section that reaches one end of the lower surface of the wiring board 2. The partition protrusion 4 a also serves to increase the bonding strength between the metal base 4 and the wiring board 2.

  Therefore, the molten resin 10 injected from the gate portion 9 is first filled on the lower surface side of the substrate 2 and then allowed to flow to the upper surface side of the substrate 2 due to the presence of the partition protrusion 4a. 7, the upper surface side of the substrate 2 is filled and overflows into the dummy cavity 11. Thereafter, resin sealing molding is performed for 3 minutes, and after the sealing molding, the submodule 7 (resin sealing type electronic control device 1) is detached from the mold 8 and an excess (such as in the dummy cavity 11) caused by overflow. Cut the resin part. Finally, post-curing is performed at 140 ° C. for 5 hours or longer as necessary.

  In the resin sealing molding method of this example, the confluence of resin flow cannot be formed inside the molded product, and molding defects such as weld voids and entrainment voids do not occur. A resin confluence is not formed inside the through hole 3 and good resin flowability is obtained.

  Normally, the pressure is preferably as high as possible in order to extrude or crush voids and the like in the pressure holding process after completion of filling, but in this example, since the voids are extruded by resin flow, a high molding pressure is not required. After the resin molding, if voids are formed and air remains, when the submodule 7 (resin-sealed electronic control device 1) is released from the mold 8, the internal pressure of the air layer is released. 4 may cause peeling or cracks on the adhesive surface, and stable resin sealing molding cannot be performed. This is because the higher the molding pressure, the higher the internal pressure of the air layer.

  From the above, it is desirable to exhaust the air layer completely. In the sealing molding method of this example, the thermosetting resin 10 is overflowed into the dummy cavity 11 and the air layer is pushed out, so that no air layer is left on the product side.

  Further, without providing the dummy cavity 11, the inside of the mold 8 clamped at the time of resin sealing molding is evacuated and depressurized to a pressure lower than the atmospheric pressure by using a vacuum pump, and a transfer mold method or a compression mold is performed under this reduced pressure. You may make it perform resin sealing molding by a system.

  By doing so, molding defects such as weld voids and entrainment voids are less likely to occur, so that the yield of the product can be improved, and the life of the apparatus can be extended, and high reliability can be achieved. Sex can be obtained.

The bird's-eye view which shows the external appearance of one Embodiment of the resin-sealed electronic control apparatus which concerns on this invention. FIG. FIG. 2 is a partially cutaway bird's-eye view of the resin-sealed electronic control device shown in FIG. 1. The longitudinal cross-sectional view of the resin-sealed electronic control apparatus shown by FIG. Sectional drawing which expands and shows the surroundings of the through hole provided in the wiring board of the resin-sealed electronic control apparatus shown by FIG. 6 is a graph provided for explaining the relationship among a molding pressure P, a board thickness t of a wiring board, and a hole diameter d of a through hole in an example of a sealing molding method for a resin-sealed electronic control device according to the present invention. The longitudinal cross-sectional view with which it uses for description at the time of resin injection | pouring filling in the other example of the sealing molding method of the resin-sealed electronic control apparatus which concerns on this invention. The longitudinal cross-sectional view with which the explanation at the time of resin charge completion in the other example of the sealing molding method of the resin-sealed electronic control apparatus which concerns on this invention is provided.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Resin sealing type electronic control apparatus, 2 ... Printed wiring board, 3 ... Through hole, 3a ... Conductor pattern, 4 ... Metal base, 4a ... Partition protrusion 5 ... Connector, 5a ... Metal terminal, 6a ... Electronic component, 6b ... Microcomputer, 7 ... Submodule, 8 ... Mold, 9 ... Gate part, 10. ..Thermosetting resin (composition), 11 ... dummy cavity, 12 ... resin tablet

Claims (7)

A wiring board having two or more wiring layers, and in order to electrically connect the wiring layers to each other, a wiring substrate provided with a number of through holes penetrating in the thickness direction and having an inner peripheral surface made of a conductor pattern; An electronic component mounted on a board; a metal base on which the wiring board is mounted; and a connector that is attached to the metal base and electrically connects the wiring board and the outside. A resin-sealed electronic control device in which a part of the metal base is integrally sealed with a thermosetting resin,
The resin-sealed electronic control device, wherein the thermosetting resin is filled in the through hole.   The resin-sealed electronic control device according to claim 1, wherein the resin-sealed electronic control device is configured as an in-vehicle engine control unit. The sealing molding method for a resin-sealed electronic control device according to claim 1, wherein a submodule including the wiring board, the metal base, and the connector is set in a mold, and the mold is placed in the mold. Molding pressure P satisfying t <2P × d / 3 (where d is the diameter of the through hole (mm), and t is the thickness (mm) of the wiring board) by injecting and filling the thermosetting resin. A sealing molding method characterized by sealing molding with (kgf / cm ² ).   The sealing molding method for a resin-sealed electronic control device according to claim 1, wherein a submodule including the wiring board, the metal base, and the connector is set in a mold, and the mold is placed in the mold. Injecting the thermosetting resin from one side of the wiring board, filling the one side, and then flowing the other side to overflow from the other side. A sealing molding method characterized by the above.   A dummy cavity is provided in the mold, and a gate portion of the mold and the dummy cavity are prevented from communicating with each other through a gap formed between the metal base and one surface of the wiring board. Therefore, the sealing molding method according to claim 4, wherein the metal base is provided with a partition projection that reaches one surface of the wiring board.   The sealing molding method for a resin-sealed electronic control device according to claim 1, wherein a submodule including the wiring board, the metal base, and the connector is set in a mold, and the mold is placed in the mold. A sealing molding method characterized in that when the thermosetting resin is injected and filled to perform sealing molding, the inside of the mold is depressurized below atmospheric pressure.   The sealing molding method according to any one of claims 3 to 6, wherein the sealing molding method is performed by a transfer mold method or a compression mold method.

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