JP2003332512A - Electronic circuit device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the generation of cracks due to exfoliation by restraining exfoliation between sealing resin and a lead frame which is caused by stress occurring in the sealing resin in a lead frame end, in an electronic circuit device. <P>SOLUTION: In the electronic circuit device, a substrate 2 on which an electronic circuit element 1 and a lead frame 3 bonded to the substrate 2 are integrally molded in a unified body by using the sealing resin 6. The main part of the end 8 of the lead frame 3 in the sealing resin 6 is formed uneven. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic circuit device, and more particularly to an electronic circuit device in which a lead frame bonded to a substrate is integrally molded with a sealing resin.

[0002]

2. Description of the Related Art As a conventional electronic circuit device, for example,
Author: Asaoni Shimura, Sueokawai, Kamimura Kami, Title: Effect of Lead Frame Material on Plastic Encapsulated Icy Package Cracking Under Temperature Cycling, Publish: IEE TRANSACTIONS ON COMPONENTS HYBRIDS AND MANUFACTURING TECHNOLOGY, 12
Volume, Issue 12, December 1989 (ASAO NISHIMURA, SUEOKAWAI, AN
D GEN MURAKAMI, plucking of Lead Frame Material on
Plastic-Encapsulated IC Package Cracking Under Tem
perature Cycling ・ IEEE TRANSACTIONS ON CONPONENT
S, HYBRIDS, AND MANUFACTURING TECHNOLOGY, VOL.12,
No. 4, DECEMBER, 1989).

This conventional electronic circuit device is shown in FIG. 18 and FIG.
This will be described with reference to FIG. FIG. 18 is a bottom view of a conventional electronic circuit device, and FIG. 19 is a sectional view of the electronic circuit device. It should be noted that the reference numerals in these figures indicate the same or corresponding parts to those of the embodiments of the present invention described later. This electronic circuit device has a structure in which the electronic circuit element 1 made of silicon and the lead frame 3 made of 42 alloy are joined with an adhesive 12, and these are integrally molded with a sealing resin 6 such as epoxy. These figures show -55 to 150 in this electronic circuit device.
The direction of the stress of the sealing resin when the temperature cycle test of ℃ is carried out is schematically indicated by an arrow.

[0004]

In the electronic circuit device according to the present invention, the encapsulating resin 6 has a stress of almost 0 due to softening at a high temperature of 150 ° C., and has a stress in a direction parallel to the surface of the lead frame at a low temperature of −55 ° C. Tensile stress 14 occurs. This is because the sealing resin 6 has a linear expansion coefficient larger than that of silicon and 42 alloy, and the sealing resin 6 has a relatively large shrinkage amount at a low temperature. This stress 14 is almost isotropic in the center of the electronic circuit device as shown in FIG.
At the end portion 8 of the lead frame 3, the stress changes into a stress perpendicular to the outline of the lead frame 3. Since the adhesive strength between the 42 alloy lead frame 3 and the sealing resin 6 is not so high, the peeling 15 may occur due to the stress 16 perpendicular to the outline of the lead frame 3. Furthermore, this peeling 15
Occurs in a wide range of the interface between the lead frame 3 and the sealing resin 6, a stress 16 perpendicular to the outline of the lead frame 3 is generated.
Is significantly concentrated, and cracks 13 are generated in the sealing resin 6 from the separated portion due to the stress 16. When this stress is repeated in the temperature cycle test, the crack 13 gradually develops and reaches the surface of the sealing resin 6. This crack 13
Finally occurs along substantially the entire outline of the lead frame end 8 as shown in the bottom view of the electronic circuit device of FIG. When the crack 13 reaches the surface of the sealing resin 6, the moisture resistance of the electronic circuit device is impaired, which causes a failure of the electronic circuit device.

An object of the present invention is to provide an electronic circuit device capable of suppressing the peeling between the sealing resin and the lead frame due to the stress generated in the sealing resin at the end of the lead frame and preventing the generation of cracks due to the peeling. It is in.

[0006]

In order to achieve the above object, the present invention provides an electronic circuit device in which a substrate on which an electronic circuit element is mounted and a lead frame bonded to the substrate are integrally molded with a sealing resin. In addition, the main part of the end portion of the lead frame in the sealing resin is formed in a concavo-convex shape.

Further, preferably, the uneven end portion has an approximately repeating shape, and the repeating cycle length of the uneven end portion is set to 2 W, and the side opposite to the substrate of the lead frame and the outer surface of the sealing resin. And t is the distance between them and a is the dimensional difference between the maximum point and the minimum point of the uneven end portion, and the uneven end portion satisfies the relationship of either or both of W <2t and a> 2W. Especially.

More preferably, the electronic circuit device has a substrate on which a silicon electronic circuit element is mounted and an alloy lead frame bonded to the substrate integrally formed with a sealing resin such as epoxy, This is because both ends of the lead frame in the resin are formed in a concavo-convex shape over the entire portion corresponding to the substrate.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A plurality of embodiments of the present invention will be described below with reference to the drawings. The same reference numerals in the drawings of each embodiment indicate the same or equivalent components.

A first embodiment of the electronic circuit device of the present invention is shown in FIG.
From now on, description will be made with reference to FIG.

The electronic circuit device of this embodiment is shown in FIGS.
As shown in FIG. 2, a substrate 2 on which a plurality of electronic circuit elements 1 made of silicon are mounted and a lead frame 3 of a copper, invar, or copper laminate bonded to the substrate 2 with an adhesive 12 are sealed with epoxy or the like. The resin 6 is integrally molded.
The substrate 2 is electrically connected to the external connection terminal 4 by the aluminum thin wire 5. A large number of external connection terminals are provided and are provided so as to project outward from the end portion 7 of the sealing resin 6.

The lead frame 3 is formed in a rectangular shape as a whole, and a hole 3a is formed in the vicinity of an end portion of a short side thereof.
As shown in FIG. 1, the major part of the long side sealed by the sealing resin 6 is formed in an uneven shape. This uneven end 8
Are formed over the entire portion of the sealing resin 6 corresponding to the substrate 2 and have an approximately repeating shape. In this embodiment, the semi-circular arc on the convex side and the semi-circular arc on the concave side are combined to have the same repeating shape. It should be noted that the hole 3 a located inside the sealing resin 6 is also formed with an uneven shape. The uneven hole 3a also has a function of suppressing peeling similarly to the uneven end portion 8.

Since the linear expansion coefficient of the substrate 2 and the lead frame 3 is close to the linear expansion coefficient of the electronic circuit element 1 mounted on the substrate 2, the sealing resin 6 has a relatively large linear expansion coefficient. Have. The electronic circuit device is
-55 ° C when a 150 ° C temperature cycle test is performed
The stress state at is like the arrow schematically shown in FIGS. That is, since the encapsulating resin 6 softens at a high temperature of 150 ° C., the stress becomes almost 0, and at a low temperature of −55 ° C., tensile stresses 14 and 16 in a direction parallel to the surface of the lead frame 3 are generated in the encapsulating resin 6. Occurs. The stress 14 generated in the center of the electronic circuit device causes a stress 16 near the end portion 8 of the lead frame. However, since the outer shape of the end portion 8 of the lead frame 3 is uneven, the stress 16 is dispersed over a wide area. As a result, the degree of concentration of the stress 16 is reduced, and the possibility of peeling between the lead frame 3 and the sealing resin 6 is reduced. Further, even if peeling occurs between the lead frame 3 and the sealing resin 6, the stress concentration of the sealing resin 6 due to the peeling is reduced, so that the cracking of the sealing resin 6 can be prevented.

Next, a second embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. It should be noted that in the description of the second embodiment, the description common to the first embodiment described above (for example, the entire shape of the electronic circuit device) will not be repeated.

In the second embodiment, the concave and convex shape of the lead frame end portion 8 is higher than that of the first embodiment (in other words, the recess is deeper) and the length of the repeating cycle is smaller. Is. As shown in FIG. 10 to FIG. 13, the cycle length of repetition of the unevenness of the lead frame end portion 8 is 2 W, and the dimensional difference between the maximum point 10 and the minimum point 11 adjacent to each other on the outer shape line (in other words, the height of the convex portion). S) is a, and the distance between the lower surface of the lead frame 3 and the lower surface of the sealing resin 6 is t, the uneven shape of the lead frame end portion 8 will be specifically described.

If the encapsulating resin 6 and the lead frame 3 are separated from each other, the stress 16 of the encapsulating resin 6 concentrates on the maximum point 10 and the minimum point 11 of the end portion 8 of the lead frame. The crack 13 may start from these points as the temperature cycle is repeated.
At the maximum point 10 and the minimum point 11, the stress 16 of approximately the same magnitude is concentrated, so cracks 13 are generated in the temperature cycle test.
Will progress from each point 10 and 11 almost at the same time.
Then, when the length of each crack 13 reaches W ′, the adjacent crack W ′ interrupts the flow of the stress 16, so that the progress of the crack 13 stops in the state shown in FIG. 11. The length W'of this crack is substantially the same as the cycle W of the uneven shape.

The crack 13 also propagates in the thickness direction of the sealing resin 6 shown in FIG. 11 under the mechanical condition that the stress at each point becomes uniform on the front edge of the crack, and as shown in FIG. It becomes almost circular. Therefore, if the uneven shape of the lead frame end portion 8 is set so that the relationship of 2t> W is established, it is possible to prevent the crack 13 from appearing on the surface of the sealing resin 6. By thus preventing the cracks 13 from appearing on the surface of the sealing resin 6, the humidity resistance of the electronic circuit device can be maintained, and the reliability can be improved.

When the crack 13 propagates to the state shown in FIG. 10, the crack 1 propagates from each maximum point 10 and minimum point 11.
Instead of the normal stress 16 for 3 disappearing, FIG.
Shear stress 17 as shown in FIG. If the crack 13 further develops due to the shear stress 17, the adjacent cracks 13 may merge as shown in FIG. In this way, whether the crack 13 further develops and merges or does not merge is determined by the relationship between the dimension W and the dimension a. This condition will be described below.

Let the tensile strength of the sealing resin 6 be σf.
The force F per width W ′ when the crack 13 is generated is calculated by the following formula.
It is represented by (1).

F = Wtσf (1) The shear stress τ due to the force F during the interval a in FIG. 13 is expressed by the following equation (2).

Τ = F / (at) (2) The relationship between the shear strength τf and the tensile strength σf of the sealing resin 6 differs depending on the sealing resin material, but normally τf is 1 / of σf.
Since the value is 2 or more, it is represented by the following equation (3).

Τf ≧ σf / 2 (3) Here, since the condition that the crack 13 does not propagate is that the shearing force τ of the equation (2) becomes τf or less, the equations (2) and (3)
By using, this condition is expressed by the following equation (4).

F / (ta) ≦ σf / 2 (4) Further, using the equation (1), the following equation (5) is derived.

A ≧ 2W (5) After all, the condition for preventing the crack 13 from further advancing due to the shear stress 17 and the adjoining cracks coalescing is expressed by the formula
It is represented by (5).

In summary, the main part of the outline of the lead frame 3 has an approximately repeating shape, the cycle length of the repetition is 2 W, and the distance between the lower surface of the lead frame 3 and the lower surface of the electronic device is t. Then, the relationship of W <2t is established, and assuming that the dimensional difference between the maximum point and the minimum point adjacent to each other on the outline is a, if the relationship of a> 2W is established, the sealing resin 6 of the end portion 8 of the lead frame is It is possible to prevent the crack 13 from developing and prevent the crack 13 from reaching the surface of the sealing resin 6.

Next, a third embodiment of the present invention will be described with reference to FIGS. 14 and 15. It should be noted that in the description of the third embodiment, duplicated description of the portions common to the above-described first embodiment (for example, the overall shape of the electronic circuit device) will be omitted.

In the third embodiment, the irregular shape of the outline of the lead frame end portion 8 is formed by a polygonal line. Since the stress at the lead frame end portion 8 can be reduced also in the third embodiment, it is possible to prevent the occurrence of cracks 13 in the sealing resin 6 due to stress concentration of the sealing resin 6 due to peeling.

Next, a fourth embodiment of the present invention will be described with reference to FIGS. In the description of the fourth embodiment, a portion common to the above-described first embodiment (for example, in the fourth embodiment, the uneven shape of the outline of the lead frame 3 is formed by a curved line. In the embodiment, since the lead frame end portion 8 is combined with the sealing resin 6, the stress of the sealing resin 6 near the lead frame end portion 8 can be further reduced as compared with the above-described first to third embodiments. The effect of preventing peeling is high, and even when peeling occurs, the effect of preventing cracks in the sealing resin 6 due to stress concentration of the sealing resin 6 accompanying peeling is high.

[0029]

As is apparent from the above description of the embodiments, according to the present invention, the peeling between the sealing resin and the lead frame due to the stress generated in the sealing resin at the end portion of the lead frame is suppressed to prevent the peeling. It is possible to obtain an electronic circuit device that can prevent the occurrence of cracks.

[Brief description of drawings]

FIG. 1 is a bottom view schematically showing a stress state of an electronic circuit device according to a first embodiment of the present invention.

FIG. 2 is a front view schematically showing a stress state of the electronic circuit device of FIG.

3 is a plan view of the electronic circuit device of FIG. 1. FIG.

FIG. 4 is a front view of the electronic circuit device of FIG.

5 is a side view of the electronic circuit device of FIG. 1. FIG.

FIG. 6 is a plan view of an electronic circuit device according to a second embodiment of the present invention.

FIG. 7 is a front view of the electronic circuit device of FIG.

8 is a side view of the electronic circuit device of FIG.

9 is a bottom view of the electronic circuit device of FIG. 6. FIG.

10 is a partially enlarged bottom view of the electronic circuit device of FIG.

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

12 is a side view of the electronic circuit device of FIG.

13 is a side view of the electronic circuit device of FIG.

FIG. 14 is a bottom view of the electronic circuit device according to the third embodiment of the present invention.

FIG. 15 is a front view of the electronic circuit device of FIG.

FIG. 16 is a bottom view of the electronic circuit device according to the fourth embodiment of the present invention.

FIG. 17 is a front view of the electronic circuit device of FIG. 16.

FIG. 18 is a plan view of a conventional electronic circuit device.

19 is a vertical cross-sectional view of the electronic circuit device of FIG.

[Explanation of symbols]

1 ... Electronic circuit element, 2 ... Substrate, 3 ... Lead frame, 4
… External connection terminals, 5… Aluminum fine wires, 6… Sealing resin, 7…
End of sealing resin, 8 ... End of lead frame, 9 ... End of substrate, 10 ... Maximum point, 11 ... Minimum point, 12 ... Adhesive agent, 13
… Crack, 14… Stress, 15… Stress, 16… Stress, 1
7 ... Shear stress.

Claims (5)

[Claims] 1. An electronic circuit device in which a substrate on which an electronic circuit element is mounted and a lead frame adhered to the substrate are integrally molded with a sealing resin, and an end of the lead frame in the sealing resin. An electronic circuit device characterized in that main portions of the parts are formed in an uneven shape. 2. The concave-convex end portion has an approximately repeating shape, and the cycle length of the repeating concave-convex shape is 2 W, and the opposite side surface of the lead frame and the sealing resin are formed. An electronic circuit device characterized in that the concave and convex end portions satisfy a relationship of W <2t, where t is a distance from the outer surface. 3. The convex-concave end portion has an approximately repeating shape, and the cycle length of repetition of the convex-concave end portion is 2 W, and the maximum point and the minimum point of the concave-convex end portion are defined as follows. The electronic circuit device is characterized in that the concave-convex end portions satisfy the relationship of a> 2W, where a is the dimensional difference. 4. The concave-convex end portion has an approximately repeating shape, and the repetition period length of the concave-convex end portion is 2 W, and the side opposite to the substrate of the lead frame and the sealing member are formed. When the distance from the outer surface of the resin is t and the dimensional difference between the maximum point and the minimum point of the uneven end portion is a, the uneven end portion satisfying the relations of W <2t and a> 2W is satisfied. Characteristic electronic circuit device. 5. An electronic circuit device in which a substrate on which an electronic circuit element made of silicon is mounted and a lead frame of a laminated body of copper, Invar, and copper adhered to this substrate are integrally molded with a sealing resin such as epoxy. The electronic circuit device is characterized in that both end portions of the lead frame in the sealing resin are formed in a concavo-convex shape over the entire portion corresponding to the substrate.