JP2003218314A - Electronic circuit device for automobile and lead frame assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic circuit device for an automobile which reduces the occurrence of thermal stress molding resin cracking or the thermal stress separation of a molding resin from an electronic circuit board or its lead frame (base) by resin-molding the electronic circuit board and the base with the molding resin into a package. <P>SOLUTION: The electronic circuit device comprises an electronic circuit composed of the electronic circuit board which has installed electronic parts, the base to which the electronic circuit is adhered, a flange which is disposed on a partial area of the base, and leads whose materials are different from those of the base, and wherein the electronic circuit is connected electrically to the leads. The leads, the electronic circuit board excluding its partial area for the flange and the flange are molded in a body by resin-molding. The base is made of Invar clad with copper on both sides, and the leads are made of copper or a copper alloy. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automobile electronic circuit device and a lead frame assembly. In particular, the present invention relates to a package structure of an electronic circuit device for an automobile, for example, an electronic circuit device which is mounted in an engine room of an automobile, a transmission or the like and controls an engine, an automatic transmission and the like.

[0002]

2. Description of the Related Art JP-A-6-61372 and JP-A-9-3
In 07026, there is one in which a semiconductor element is mounted on a substrate and sealed with resin. Further, JP-A-6-132460, JP-A-7-58274, and JP-A-7-2497.
No. 27 and Japanese Patent Laid-Open No. 10-284668 describe electronic circuit devices.

[0003]

The technique of encapsulating and mounting even a much larger area of an electronic circuit board and a base with a single molding resin has a great problem. When the mounting technology is realized, the shrinkage stress of the epoxy resin (mold resin) that wraps the circuit board and the base is large due to the size of the area of the circuit board and the base as described above, which causes a boundary between the circuit board and the epoxy resin. There is a new problem that peeling occurs on the surface or resin cracks occur. In addition, there is a problem that peeling and resin cracks similar to the above occur even under thermal stress due to repeated use environment conditions, especially temperature changes.

An object of the present invention is to package an electronic circuit board and even its lead frame (base) with a mold resin so that peeling between the mold resin and the circuit board or base due to thermal stress and resin cracks in the automobile can be reduced. It is to provide a circuit device.

[0005]

In order to achieve the above object, the present invention provides an electronic circuit comprising a circuit board on which electronic circuit elements are mounted, a base to which the electronic circuit is bonded, and a part of the base. And a lead made of a material different from that of the base, the electronic circuit and the lead are electrically connected, and the circuit board and the lead are partially removed. In the structure in which the lead and the flange are collectively embedded in the mold resin, the base is made of a material in which copper is laminated on both surfaces of the invar, and the lead is made of a material of copper or a copper alloy.

More preferably, the circuit board is composed of a multi-layer circuit board made mainly of glass ceramic or ceramics, and the base and the lead are integrated by plastic bonding before being embedded in the mold resin. Is
The feature is that both are separated after burial.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of controlling an automatic transmission of an automobile by an electronic circuit is widely adopted, and there are various mounting structures of the electronic circuit. In the electronic circuit device directly attached to the transmission, the mounting place is selected so that the electronic circuit is not damaged by the intrusion of water, oil, or the like, and the electronic circuit device is structured so that they do not infiltrate.

As an example of the structure, an electronic circuit board is mounted on a metal base, the base and the cover are resistance-welded or laser-welded to hermetically seal the inside of the electronic circuit device, and nitrogen or the like is used. There is known a so-called hermetic seal structure in which an inert gas of

In this structure, the input / output terminals of the electronic circuit are led out through the through holes provided in the base, and the through holes are sealed with glass having a high insulation resistance. Therefore, it is necessary to optimally select the linear expansion coefficient of the base, the glass, and the terminal. That is, several 100 ° C. to 1000
This is because it is necessary to cause residual compressive stress to act between the three parts when the glass is melted at a high temperature of ° C and returned to room temperature.

These materials are limited. For example, when soda-barium glass is used as the sealing material, the base material is a steel plate, and the terminals are a combination of iron-nickel alloy (iron 50% -nickel 50%).

Therefore, it is necessary to prevent oxidation at high temperatures, and the base is required to be plated with nickel having a high melting temperature.

Further, in the welding, the combination material of the cover is limited, and the same steel plate as the base is used. When there are many heating elements in the electronic circuit, aluminum, copper or the like is suitable as the base material for facilitating heat dissipation, but as described above, steel plates have to be used, and the steel plates have poor heat dissipation.

Further, in the resistance welding, there is a factor of cost increase such that the flatness accuracy of the base and the cover must be high so that the electrical contact resistance between them is uniform.

In laser welding, variations in the thickness of the nickel plating applied to the base affect welding, and
The bead of the welded part is exposed. A protective coating is required to prevent rusting due to it.

It is difficult to reliably judge the quality of welding from the appearance. To check the airtightness, a check method using helium gas, a bubble leak check for checking the presence or absence of bubbles in an inert liquid Laws were needed.

In order to improve the above-mentioned various points, a circuit board on which an electronic circuit element is mounted is adhered to a base made of a material having good thermal conductivity, and while exposing one side of the base,
A packaging technique has been proposed in which a circuit board and a base are sealed with an epoxy resin (mold resin).

However, in this case, for example, a silicon chip is used as an electronic circuit element, a glass ceramic substrate having a linear expansion coefficient similar to that of the silicon chip is used as a circuit substrate, and these members are sealed with an epoxy resin. The structure had the following problems.

That is, during the molding process (transfer molding process) of the epoxy resin for embedding the circuit board or base, the molding resin (epoxy resin) is taken out from the mold through the curing process, and the epoxy resin is cooled during cooling. Due to the curing shrinkage and the difference in linear expansion coefficient with respect to the substrate or base, peeling or resin cracks occur at the interface between the epoxy resin and the circuit board or base.

This is because the epoxy resin equivalent linear expansion coefficient at the time of molding (the epoxy resin equivalent linear expansion coefficient is
The chemical shrinkage of the resin at the molding temperature until the mold resin is taken out of the mold and cooled to room temperature, and the molding temperature ~
It is a combination of the linear expansion coefficient α1 up to the glass transition temperature Tg and the linear expansion coefficient α2 between the glass transition temperature Tg and room temperature, which is about 4 times the linear expansion coefficient at room temperature) The linear expansion coefficient of the circuit board is smaller than that of the base, and the linear expansion coefficient of the circuit board is smaller than that of the base. The tensile stress acts on the weak part of the surface, and peeling occurs at the boundary surface.

In order to eliminate this peeling, for example, if a film treatment with good adhesion is formed on the end face portion of the base, there is a problem that cracks occur in the epoxy resin near the boundary surface.

As a countermeasure, it is conceivable to use an epoxy resin having a small curing shrinkage and a small linear expansion coefficient, or to apply a flexible resin coating treatment to the end surface of the base to absorb the difference in the linear expansion coefficient. However, in any case, cost increase is inevitable, and an inexpensive structure has been desired.

In the prior art, a semiconductor device is mounted on a lead frame and these components are embedded in a mold resin to be packaged, as disclosed in, for example, Japanese Patent Laid-Open No. 7-240493. Kaihei 1-205556
There is a package of an IC chip, its mounting member, and a heat radiating plate, as disclosed in Japanese Patent Publication No. JP-A-2003-242242. These conventional techniques do not attempt to package the electronic circuit board and even the base thereof with the molding resin.

Based on the above, the first embodiment is shown in FIGS. 1 to 22.

FIG. 1 is a plan view of an automobile electronic circuit device (control unit) 1 according to this embodiment, and FIGS. 2 and 3 are partial cross-sectional side views in which the viewing direction is changed.

An electronic circuit 5 including a circuit element 6 and a circuit board 7 is mounted on a base 2 having a flange portion 2d. This mounting is performed by adhering the circuit board 7 onto the base 2. The circuit board 7 has a structure in which only the portion of the base 2 is adhered to the partially raised area of the central portion of the base 2. This structure will be described later.

Reference numeral 3a is a lead (terminal). When electrically connecting to an external connection object (not shown), the lead 3a is fitted to a harness connector of the external object, or a harness terminal. It is connected by welding or the like.

The electronic circuit 5 and the lead 3a are electrically connected to each other through the aluminum thin wire 9 by a wire bonding method such as thermocompression bonding or ultrasonic wave.

After the electronic circuit 5 is adhered to the base 2 and the electronic circuit 5 and the lead 3a are connected by the thin aluminum wire 9, these parts (circuit element 6, circuit board 7, base 2, lead 3a) are collectively packaged. Then, it is embedded in a mold resin (hereinafter referred to as a sealing resin) 4 except for a part of the lead 3a and a part of the flange 2d.

The sealing resin 4 is manufactured by transfer molding. Transfer molding is generally a method of using a thermosetting resin such as an epoxy resin as a sealing resin, and a tablet-shaped epoxy resin obtained by compression molding powder is melted by applying a predetermined temperature and pressure. To flow and solidify in the mold.
This manufacturing method is widely adopted as a package of a chip such as an LSI (Large Scale Integrated Circuit).

The sealing resin 4 is a resin having a particularly low coefficient of linear expansion and entirely encloses the internal parts. The encapsulating resin 4 keeps the adhesive force with the internal parts at a predetermined value at all times, and also peels off or breaks due to thermal stress at the soldering portion or the thin wire bonding connection portion between the semiconductor chip and the circuit board. The optimum physical property value is selected to prevent the occurrence of

The electronic circuit device for automobiles has the sealing resin 4, the lead 3a and the base 2 which are repeatedly subjected to thermal stress during use.
There is a concern that water, oil, etc. may enter from the respective contact interfaces with and. Regarding this point, the difference in linear expansion coefficient between the lead 3a and the base 2 and the sealing resin 4 is made as small as possible to reduce the thermal stress between these members, and the lead 3a and the base 2 are subjected to a special surface treatment (for example, Aluminum chelate treatment) and covalent bond at the boundary between the resin and the member can be solved.

For the lead 3a, copper or a copper-based alloy material having good thermal conductivity is selected. The circuit board 7 is made of a material having a relatively small coefficient of linear expansion, such as ceramic or glass / ceramic, and has a predetermined circuit pattern. The base 2 to which the circuit board 7 is bonded has a linear expansion coefficient of the circuit board 7
And a resin close to the sealing resin 4 is selected. For example, a material in which copper is laminated on both sides of Invar (iron 64% -nickel 36% alloy), that is, a so-called clad material is selected, and the desired linear expansion coefficient is changed by changing the thickness ratio of both metals. obtain. By the way, the linear expansion coefficient of the material alone is about 1 ppm / ° C for Invar and 16.5 ppm / ° C for copper.

To reduce the linear expansion coefficient, the thickness of copper is reduced and the thickness of Invar is increased. Therefore, in the first embodiment of the present application, for example, when the linear expansion coefficient of the circuit board 7 is 7 ppm / ° C and the linear expansion coefficient of the sealing resin 4 is 8 ppm / ° C, the linear expansion coefficient of the clad material is 10.6 ppm / ° C. It is about degree. As an example of the clad material for obtaining this linear expansion coefficient, when the thickness of the base 2 is 0.6 mm, the thickness of each of the invar and the copper is 0.2 mm.

When the coefficient of linear expansion of the clad material having a value close to that of the circuit board 7 and the sealing resin 4 is selected to be about 8 ppm / ° C., the difference in coefficient of linear expansion between them becomes small, and the environmental conditions, especially the temperature change. The thermal stress due to the repetition of the above is reduced, and the resistance against the crack of the sealing resin 4 and the peeling of the adhesive interface with the member is increased.

In this case, it is necessary to reduce the thickness of copper. For example, when the total thickness is 0.6 mm, the invar thickness is 0.3 mm and the copper thickness is 0.15 mm. Becomes When the amount of copper is small, the thermal conductivity is small, and when the circuit element 6 is a high heat generating element, the temperature rise value is high. Therefore, in the case of this embodiment, the thickness of each of the invar and copper of the clad material is adjusted. Selected to 0.2mm.

However, when the temperature rise is not a problem, the linear expansion coefficient is 8 ppm / ° C. to prevent the crack of the sealing resin 4 caused by the thermal stress and the peeling of the interface with the member.
It is preferable to select the degree.

Therefore, the thicknesses of the invar and copper of the clad material may be selected to the optimum values according to the temperature rise of the circuit element 6.

Since the clad material is formed by laminating soft copper and hard Invar, there is a large difference in hardness between the materials, and there is a problem that the punching workability of the press is poor. Generally, in the punching process of a press, the machined surface has a drooping surface, a shearing surface, and a fracture surface, so that a predetermined shape can be formed. However, when punching out the clad material, it is equivalent to punching thin plates with a large difference in hardness at the same time, and the droop face, shear face, and fracture surface become ambiguous, and there is a problem that the joint part between the plates is easily separated at the punched end face. Occurs.

For example, the hardness of the invar is Hv (Vickers hardness) of 200 and that of copper is about Hv50, but the lead 3a has a shape in which a large number of narrow width portions are arranged, and it is difficult to punch with high precision. Become. As a countermeasure against this, in the present application, the portion of the base 2 which has a simple shape and does not require high precision is used as a clad material, and the leads 3a which require high precision are made of copper or copper alloy material.

A general lead frame structure is one in which the base portion 2 and the lead portion 3a are integrally pressed with the same copper alloy material, but the linear expansion coefficient thereof is 17 ppm /
Around ℃, larger than the circuit board 7 and the sealing resin 4,
Resin cracks due to repeated thermal stress during use and peeling at the interface with the resin are likely to occur. In particular, the base portion 2 has a large area, and the thermal stress acting on the adhesion interface with the sealing resin 4 is large. The lead portion 3a has a small area, which is not a problem in the structure of the first embodiment of the present application.

FIG. 4 is a sectional view of an essential part of an electronic circuit device according to this embodiment, which corresponds to FIG.

The circuit board 7 is bonded to the upper surface of the base portion 2 with an adhesive 8. The circuit board 7 has a structure in which only the portion of the base 2 is adhered to the partially raised area of the central portion of the base 2. In general, when the substrate is adhered to the base, the entire surface is adhered, but in the first embodiment of the present application, it is partially adhered.

In the structure in which the entire surface is adhered, it is difficult to adhere the interface between the adhesive and the member without a gap, and an air layer is formed at the interface when the adhesive is cured, and a large number of minute bubbles are present in the adhesive. It remains. For this reason, the problem that the bubbles are expanded and crushed by the heat of the transfer molding step and the interface is peeled off near the adhesion interface between the adhesive portion and the sealing resin 4 is likely to occur.

The base 2 is provided with a large number of small holes 2g, and the sealing resin 4 is filled in the small holes 2g. Due to the existence of the small holes 2g, the base 2 of the area corresponding to the area of the circuit board 7 is configured with low rigidity. Since the rigidity is low, the thermal stress due to the difference in linear expansion coefficient with the sealing resin 4 is easily absorbed, and a large number of small holes 2g are provided in a dispersed manner. Has the advantage of being very large. It should be noted that a part of the small hole 2g also serves as a hole into which a jig is inserted in the step of adhering the circuit board 7 and the wire bonding step of the aluminum thin wire 9, as will be described later.

A wiring pattern (not shown) is formed on the circuit board 7, and the circuit element 6 and the bonding pad 10 are soldered on the board. A thin wire 9 made of an aluminum material is connected to each of the bonding pad 10 and the lead 3a by a wire bonding method such as thermocompression bonding or ultrasonic wave.

It is preferable that the material of the circuit board 7 has a coefficient of linear expansion close to that of a silicon chip occupying most of the circuit element 6 and has a small difference in coefficient of linear expansion from the sealing resin 4. A multi-layer circuit board is preferable for downsizing as the circuit scale becomes large, and a ceramic or glass-ceramic board is preferable. If heat dissipation is important, a ceramic substrate having a large thermal conductivity is preferable.

FIG. 5 shows a shape in which the base 2 and the lead frame 3 are joined and integrated.

The base 2 includes a board mounting portion 2 ', a flange portion 2d, a positioning hole portion 2f, an engaging portion 2e, and a large number of small holes 2.
g, a shape having a substrate bonding portion 2h. 2g of small holes
The circuit boards 7 are provided in a dispersed manner corresponding to the area of the circuit board 7 for the purpose of preventing interfacial peeling. The lead frame 3 includes a lead 3a, a bonding pad portion 3b, a connecting portion 3c,
It consists of a frame part 3d, an engaging part 3f, and a notch 3e,
Each of these is manufactured by pressing. And both engaging parts 2
e, 3f are combined and integrated.

The bonding pad portion 3b for connecting the thin wire 9 made of an aluminum material by wire bonding is partially plated with nickel or silver so that the surface thereof is not oxidized. The flange portion 2d is fixed to a mating member, and the hole 2f is provided for positioning a jig during assembly.

The notch 3e determines the directionality, and is provided for the purpose of reducing a die alignment error at the time of transfer molding, which is caused by a production error. Also, the circuit board 7
It also serves the purpose of preventing the assembly from being bonded in the opposite direction when set in this mold after the wire bonding work is completed. When the lead frame 3 has a symmetrical shape, the notch 3e may be selected to have an arbitrary shape and position that can identify the front and back.

The reason why the connecting portion 3c, the frame portion 3d and the flange portion 2d have a closed loop structure is that the sealing resin 4 is used for transfer molding by tightening this portion from above and below with a transfer molding die. This is to prevent the epoxy resin from leaking to the outside of the closed loop portion when the epoxy resin melts and becomes liquid in the mold.

Since a fitting gap is formed between the narrow portion of the lead 3a to be fitted and the mold, liquid epoxy resin leaks to the outside at this portion, but due to the closed loop structure, It remains as a thin burr after curing in the loop. After this molding, the connecting portion 3c and the frame portion 3d of the lead frame 3 are cut to form a plurality of independent leads 3a, and the flange portion 2 of the base 2 is formed.
The control unit 1 is completed by subjecting d to a predetermined shape through a window punching process and a bending process.

FIG. 6 is a detailed view of a portion where the base 2 and the lead frame 3 are joined, and FIG. 7 is a sectional view taken along the line AA of FIG.

The engaging portion 2e provided on the base 2 has a convex shape and is fitted into the engaging portion 3f (concave shape) of the lead frame 3.
An inclined portion is provided on each of the convex and concave portions so that they can be locked in the planar direction. Then, by applying a press load, the copper 2b, 2c of the engaging portion 2e is crushed in the thickness direction,
The recess 13 is formed and joined. Even if the concavo-convex shapes of the engaging portions are installed in reverse, the same coupling effect can be obtained.

The crushed portion is a part of the convex shape, and the material hardness thereof must be lower than that of the concave material,
When a pressing load is applied, the recess opens outward, and there is a problem that sufficient bonding cannot be achieved. In the present application, in consideration of this, the lead frame 3 includes the copper portion 2b of the clad material,
Material with hardness higher than 2c is selected. As an example,
It is a copper alloy having an Hv (Vickers hardness) of 150.

The clad material of the base 2 is made of Invar 2a, copper 2b and 2c, is formed by laminating by applying a predetermined temperature and pressure as is well known, and is firmly bonded by diffusion between metal materials. . By crushing the coppers 2b and 2c to form the recesses 13 on the upper and lower sides, the material causes a plastic flow, the fitting gap in the plane direction is filled, and the base 2 and the lead frame 3 are joined.

An example of a method of forming the recess 13 is shown in FIG.

Reference numeral 11 is a lower mold, and 12 is an upper mold, which has a stepped shape. When a load is applied from above and below, the copper portions 2b and 2c are crushed and the recess 13 is formed. The press conditions are set so that the stepped portions of the molds 11 and 12 contact the upper and lower surfaces of the lead frame 3 and the upper and lower surfaces of the base 2 when a predetermined load is applied. Otherwise, the copper portions 2b and 2c may locally bulge in the thickness direction in the vicinity of the fitting portion, causing distortion in the thickness direction.

In the drawings, the material is shown to have the same thickness, but either the base 2 or the lead frame 3 may be thickened. When it is necessary to enhance heat dissipation, it is effective to make the base 2 thick. Further, when the lead 3a is connected to the connector, the thickness can be adjusted to the compatible thickness of the mating female terminal.

FIG. 9 shows the manufacturing shape of the lead frame 3, FIG.
Reference numeral 0 denotes a manufacturing shape of the base 2, which is manufactured by punching with a press.

The lead frame 3 includes a lead portion 3a, a bonding pad portion 3b, a joint portion 3c, and a frame portion 3
It has d, a notch 3e, and an engaging portion 3f. The part connected by the dotted line is an empty part for continuous press working. The bonding pad portion 3b needs to be nickel-plated, silver-plated or the like to prevent oxidation, but it may be partially applied in a strip shape in the material state before the press working, or may be partially plated after the press working. May be.

The base 2 includes a circuit mounting portion 2'and an engaging portion 2
e, flange 2d, positioning hole 2f, many small holes 2g,
It has a substrate bonding portion 2h. Similar to the lead frame 3, it may be shaped so as to have an empty portion for continuous press working.

As described above, since the base and the lead are made of different materials and integrated with each other by the plastic coupling, the physical properties of the circuit board and the sealing resin, the required level of heat radiation and the mating connector terminal are used. Therefore, the materials of the base and the lead can be selected with the optimum linear expansion coefficient, thermal conductivity and thickness. This is a great effect that cannot be achieved by the conventional one in which the lead frame is made of the same copper alloy material.

FIG. 11 is a plan view showing details of the adhesive portion 2h of the base 2, and FIG. 12 is a sectional view taken along line BB thereof.

Butterfly-shaped window 2i, narrow narrow window 2j, inclined portion 2
k, a bonding area 2l extending in the horizontal direction is formed.
Since the inclined portion 2k forms a narrow space between the butterfly-shaped window 2i and the narrow small window 2j, it has low rigidity and acts like a kind of leaf spring. This is because the adhesive 8 and the circuit board 7 are adhered,
The purpose is to prevent the peeling of the adhesive due to the thermal stress due to the difference in linear expansion coefficient between the members in the use state after being molded with the sealing resin 4.

FIG. 13 is a plan view showing an example of a jig for adhering the circuit board 7, and FIG. 14 is a sectional view taken along line CC of FIG.

First, the state shown in FIG. 5 in which the base 2 and the lead frame 3 are combined is positioned on the bonding jig 15, and when this is released, the pin 15a penetrates the positioning hole 2f of the base 2. Next, the pins 15b penetrate through a part of the small holes 2g provided in the base 2, and the lower surface of the base 2 and the lower surface of the lead frame 3 contact the upper surface of the bonding jig 15.

Although two pins 15a are installed here, four pins 15a may be installed so as to penetrate all four positioning holes 2f.

Thereafter, the adhesive 8 is applied to the adhesive area 21 of the base 2.
Apply to. When the circuit board 7 is placed, the pins 15b
It stops by touching the head of. This pin 15b is connected to the circuit board 7
In the embodiment, four pieces are installed so as to be located at the four corners of. The application of the adhesive 8 may be performed before the assembly in the bonded state is mounted on the bonding jig 15. It is effective to apply a load to a part of the upper surface of the circuit board 7 so that the adhesive 8 becomes compatible with the circuit board 7 and the adhesion region 21. Although the positioning of the circuit board 7 in the plane direction is not shown, it can be easily configured by providing a pin of an arbitrary shape penetrating the small hole 2g.

A large number of pins 15a and 15b are provided on the bonding jig 15, and preparation is made so that a large number of circuit boards 7 can be bonded at the same time. Curing of the adhesive 8 is completed by applying a predetermined temperature and time.

FIG. 15 is a plan view showing a jig for wire bonding work, and FIG. 16 is a DD sectional view thereof.

The assembly after the adhesive curing process is placed on the lower jig 16a of the bonding jig 16. First base 2
When the pin 16c penetrates the positioning hole 2f of the
Also, the lower surface of the lead frame 3 contacts the upper surface of the lower jig 16a. Next, the base 2 and the lead frame 3 are pressed by the upper jig 16b, and are fixed so as not to move in the vertical direction and the planar direction by using a clamp jig (not shown).

Then, the pin 16d is pushed up so that the head of the pin 16d contacts the lower surface of the circuit board 7. By combining the lock mechanism, the pin 16d
It is easy to rest (not shown). Pin 16
6 are installed at four corners of the circuit board 7 and two lower surfaces near the bonding pad 10 in the central portion.

In the wire bonding work, the circuit board 7 is pressed with a load of several hundred grams by the bonding capillary through which the fine wire 9 penetrates, but the circuit board 7 is deformed by the pressing load because it is supported by the pin 16d. Can be prevented. For wire bonding work, any method such as thermocompression bonding and ultrasonic wave is adopted, and the thin wire 9 made of aluminum material is electrically connected between the bonding pad 10 of the circuit board 7 and the lead 3a.

Specific dimensions of the first embodiment are shown in FIGS.
2 shows. The unit is mm.

FIG. 17 is a plan view of the control unit 1, FIG. 18 is a partial sectional side view thereof, FIG. 19 is a view showing a state in which the base 2 and the lead frame 3 are coupled, and FIG. 20 is a small hole 2g of the base 2. 21 is a plan view of the adhesive portion 2h, and FIG. 22 is a sectional view taken along line EE thereof.

23 to 29 show the second embodiment.

The difference from the first embodiment is the structure in which the circuit board 7 is bonded to the base 2. In the first embodiment, the circuit board 7 is adhered only to the central portion of the base 2, but in the second embodiment, it is adhered to the entire surface. In the structure where the entire surface is bonded, it is difficult to bond the interface between the adhesive and the member without any gap, and an air layer is formed at the interface when the adhesive is cured, or many minute bubbles remain in the adhesive. . For this reason, the problem that the bubbles are expanded and crushed by the heat of the transfer molding process and the interface is peeled off near the adhesion interface between the adhesive portion and the sealing resin 4 is likely to occur.

However, in the bonding operation step, the adhesive 8 is made into an epoxy adhesive sheet having a thickness of several tens of μm, a pressing load is applied from the upper surface of the circuit board 7, and a predetermined temperature and time are applied, whereby The problem can be solved. In that case, the work sequence for constructing the electronic circuit 5 is different from that in the first embodiment.

In the first embodiment, the assembly in which the circuit element 6 is mounted on the circuit board 7 is adhered to the base 2. In the second embodiment, the circuit element 6 is mounted after the circuit board 7 is bonded to the base 2. For mounting the circuit element 6, solder, silver paste or the like is selected in order to make electrical connection with the pattern of the circuit board 7, but this construction method is also possible in the second embodiment.

FIG. 23 is a plan view showing a state in which the base 2 and the lead frame 3 are joined together.

The base 2 has a shape having no small holes on the substrate mounting surface 2 '. The positioning hole 16 is installed in the same manner as in the first embodiment. Further, the engaging portions 2e and 3f are installed in the opposite manner to that of FIG.

When the linear expansion coefficient of the base 2 is selected to be substantially the same as that of the circuit board 7 and the sealing resin 4, for example, when the circuit board 7 is 7 ppm / ° C and the sealing resin 4 is 8 ppm / ° C,
The base 2 is preferably 8 ppm / ° C.

In this case, when the total thickness is 0.6 mm, the invar thickness is 0.3 mm and the copper thickness is 0.15 mm.
Becomes When the amount of copper is small, the thermal conductivity is small, and when the circuit element 6 is a high heat generating element, the temperature rise value is high, but the circuit board 7 is not adhered only partially as in the first embodiment. Since it is adhered to a large area of the base 2, heat dissipation is improved.

FIG. 24 shows an example of a method for adhering the circuit board 7 to the base 2.

First, the assembly in which the base 2 and the lead frame 3 are combined is placed on the upper surface of the bonding jig 20. The adhesive sheet 8'is placed on the base 2 and the circuit board 7 is placed thereon. Then, the jig 21 applies a load to the upper surface of the circuit board 7. In this state, the adhesive sheet 8'is melted and cured by applying a predetermined temperature and time, and the adhesive process is completed.

The material of the circuit board 7 is glass ceramic,
Since the ceramic has a high Young's modulus and a load is applied,
Since the adhesive sheet 8'is easily broken, the adhesive sheet 8'has a physical property value that can be melted and cured under a low load in consideration of this point. Further, for example, the surface of the jig 21 is coated with a heat-resistant resin having high elasticity so that the conductor pattern formed on the circuit board 7 is not scratched or the glass film for protection is not broken. There is a need.

Here, an example of selecting the adhesive sheet 8'will be described.

Epoxy adhesive is the main component, and the thickness is 5
It has a size of 0 to 200 μm and has substantially the same area size as the circuit board 7. Generally, this type of adhesive sheet has a structure in which both sides of the adhesive are sandwiched by a polyester resin film having a thickness of several tens of μm. One surface of this film is peeled off, this surface is placed on the base 2, and the roller is pressed from the upper surface through the film on the opposite surface with a roller, or is pressed with a pressing machine to temporarily bond. At this time, if the complete curing condition is, for example, 150 ° C. for 1 hour, temporary bonding can be performed by pressing in an atmosphere of 50 ° C. for several seconds. Further, it is possible to perform the above-mentioned steps without going through this temporary adhesion step.

As described above, in the case of the liquid adhesive, an air layer is formed at the interface at the time of curing or a large number of fine air bubbles remain in the adhesive, but a sheet-like adhesive is formed at a high temperature while applying pressure. Curing the adhesive will solve this problem.

After this bonding step is completed, paste solder is printed on a predetermined wiring pattern of the circuit board 7, components such as the circuit element 6 and the bonding pad 10 are mounted, and the solder is melted in a reflow furnace and solidified at room temperature. Then, electrical connection is performed. FIG. 25 shows the completed state.

FIG. 26 shows a situation where the aluminum thin wire 9 is wire-bonded, and corresponds to FIG. 16 of the first embodiment in the EE cross section of FIG. The procedure of the wire bonding work is the same as that described with reference to FIG.

FIG. 27 shows a second embodiment in which the base 2 and the lead frame 3 are integrally connected.

First Embodiment In FIG. 6, the engaging portion is formed with the convex portion on the base 2 and the concave portion on the lead frame 3, but this drawing is formed in reverse. The reason for this will be described below.

When the linear expansion coefficient of the base 2 is selected to be 8 ppm / ° C., when the overall thickness is the same as that of the first embodiment, for example, 0.6 mm, the thickness of the copper 2b is 0.15 mm and the invar 2a is 2a. Has a thickness of 0.3 mm, and the copper portion is thinner than in the first embodiment. Therefore, when the convex portion of the copper 2b is crushed to form the recess 13, the bonding force with the lead frame 3 becomes weak.

Since the hardness of the invar 2a is harder than that of the lead frame 3, there is no problem in crushing the convex portion formed on the lead frame 3. In particular, when the material of the lead frame 3 is copper, it is softer than a copper alloy. Therefore, when the recess is formed in the lead frame 3 as shown in FIG. 6, there is a problem that the engaging portion 3f opens outward.

Therefore, according to the thickness ratio of the clad material of copper and Invar, and the material hardness of the lead frame 3, the concave portion 1 is formed.
3 is formed on either the lead frame 3 or the base 2.

FIG. 28 is a sectional view taken along the line FF in FIG. 27, and FIG. 29 is a method for forming the recess 13, which is the same as that in the first embodiment.

[0099]

According to the present invention, an electronic circuit board and its lead frame (base) are also packaged with a mold resin, and peeling between the mold resin and the circuit board or base due to thermal stress and resin cracks are less likely to occur in an automobile. An electronic circuit device for use can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view showing a part of an electronic circuit device for an automobile,
The top view of 1st Example.

FIG. 2 is a partial vertical cross-sectional side view of FIG.

FIG. 3 is a partial cross-sectional side view of FIG.

FIG. 4 is a cross-sectional view of a main part of the first embodiment.

FIG. 5 is a plan view of the first embodiment showing a shape in which a lead frame and a base are integrated.

FIG. 6 is a detailed view showing the coupling portion of FIG.

7 is a cross-sectional view taken along the line AA of FIG.

FIG. 8 is a cross-sectional view of the first embodiment illustrating a method of forming a recess for joining.

FIG. 9 is a plan view of the first embodiment showing the shape of the lead frame.

FIG. 10 is a plan view of the first embodiment showing the shape of the base.

FIG. 11 is a plan view of the first embodiment showing details of the adhesive portion of the base.

12 is a sectional view taken along line BB of FIG.

FIG. 13 is a plan view showing a jig for bonding a circuit board and a first embodiment of the bonding work.

14 is a cross-sectional view taken along line CC of FIG.

FIG. 15 is a plan view of a jig for wire bonding work and a first embodiment showing the work state.

16 is a cross-sectional view taken along line DD of FIG.

FIG. 17 is a plan view of the first embodiment showing specific dimensions of the control unit.

18 is a partial cross-sectional side view of FIG.

FIG. 19 is a diagram of a first embodiment showing specific dimensions of a coupled state of a base and a lead frame.

FIG. 20 is a detailed view of the first embodiment showing specific dimensions of the base small holes.

FIG. 21 is a plan view of the first embodiment showing specific dimensions of the base adhesive portion.

22 is a cross-sectional view taken along the line EE of FIG.

FIG. 23 is a plan view of the second embodiment showing the combined shape of the base and the lead frame.

FIG. 24 is a cross-sectional view of the second embodiment showing a state of adhering substrates.

FIG. 25 is a plan view of the second embodiment showing a state where electronic circuit elements are mounted on a substrate.

FIG. 26 is a cross-sectional view of a jig for wire bonding work and a second embodiment showing the work state.

FIG. 27 is a plan view showing details of the connecting portion in FIG. 23.

28 is a cross-sectional view taken along the line FF of FIG.

FIG. 29 is a cross-sectional view of a second embodiment illustrating a method of forming a recess for joining.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Control unit (electronic circuit device), 2 ... Base, 2d ... Flange part, 2e ... Base engaging part, 3 ... Lead frame, 3a ... Lead, 3f ... Lead frame engaging part, 4 ... Sealing resin 5, ... Electronic circuit, 6 ... Circuit element,
7 ... Circuit board, 9 ... Aluminum fine wire.

Claims (5)

[Claims] 1. An electronic circuit comprising a circuit board on which electronic circuit elements are mounted, a base to which the electronic circuit is adhered, a flange portion provided on a part of the base, and a lead made of a material different from the base. And a structure in which the electronic circuit and the lead are electrically connected, and the circuit board, the lead, and the flange are collectively embedded in a mold resin except for a part of the lead and the flange. ,
An electronic circuit device for an automobile, wherein the base is made of a material in which copper is laminated on both sides of the invar, and the leads are made of a material of copper or a copper alloy. 2. The electronic circuit device for an automobile according to claim 1, wherein the base and the lead are integrated by plastic bonding before being embedded in the molding resin, and are separated after being embedded. 3. The electronic circuit device for an automobile according to claim 1, wherein the circuit board is made of glass ceramic or a material mainly composed of ceramic. 4. The automobile electronic circuit device according to claim 1, wherein the circuit board is a multilayer circuit board. 5. An electronic circuit composed of a circuit board on which an electronic circuit element is mounted, a base to which the electronic circuit is bonded, a flange portion provided on a part of the base, and a lead made of a material different from the base. And an electronic circuit electrically connected to the lead, wherein the circuit board, the lead, and the flange are collectively embedded in a mold resin except for a part of the lead and the flange. In the electronic circuit device, the base is a material in which copper is laminated on both sides of the Invar, and the lead is made of a material of copper or a copper alloy, before being embedded in the mold resin,
A lead frame assembly, wherein the base and the lead are integrated by plastic bonding.