JPH0338745B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a method for manufacturing a heat sink, and particularly to a method for manufacturing a heat sink used for hybrid integrated circuits and the like.

(b) Prior Art As shown in FIG. 1, a conventional hybrid integrated circuit includes an insulating substrate 1 made of ceramics or aluminum whose surface is anodized, a conductive path 2 provided in an arbitrary shape on the substrate 1, and a conductive path 2 provided in an arbitrary shape on the substrate 1. A heat sink 3 fixed on the conductive path 2 with solder, a power transistor 4 fixed on the heat sink 3, a sealing resin layer 5 covering and protecting the power transistor 4, and bonded to the peripheral edge of the substrate 1 with an adhesive sheet 6. and a lid body 7 that covers the entire body.

Hybrid integrated circuits with such a structure have been evaluated as having sufficient sealing for electronic equipment such as televisions, radios, stereos, etc. that have relatively favorable usage environments. However, it cannot be said that the sealing structure is sufficient for items such as electrical components of automobiles, which are used in extremely poor environments, and deterioration of power transistors, which consume electric power, has become a serious problem. That is, as a result of the heat cycle, cracks occur in the sealing resin layer 5, solder oxidation occurs due to oxygen entering through the cracks, and the thermal resistance between the power transistor 4 and the heat sink 3 increases, resulting in secondary destruction of the power transistor 4. It is.

(c) Object of the Invention The present invention was made in view of the above, and an object of the present invention is to provide a simple method for manufacturing a heat sink that realizes a good sealing structure for a power transistor incorporated into a hybrid integrated circuit.

(d) Structure of the Invention According to the present invention, a groove is formed on the upper surface of the heat sink on a flat plate, and the inner end of the groove is pressed to form a reverse tapered surface.

(E) Embodiment According to this embodiment, as shown in FIG. 2A, a flat heat sink 13 made of a copper piece 13 mm square and 3 mm thick is prepared. As shown in FIG. 2B, grooves 19 are formed on the upper surface of the heat sink 13 by pressing, either continuously or discontinuously around the periphery. The groove 19 is formed in an inverted trapezoid shape with a width of about 500 μm and a depth of about 300 μm. Subsequently, as shown in FIG. 2C, the inner end of the groove 19 is partially flat-pressed to form a reverse tapered surface 18 by utilizing the deformation caused by the pressing.

Note that the reverse tapered surface 18 may be formed on either the inner slope or the outer slope of the groove 19.

The heat sink 13 according to the present invention described above is the third heat sink 13 according to the present invention.
As shown in the figure, it is incorporated into a hybrid integrated circuit. The hybrid integrated circuit includes an insulating substrate 11 made of ceramics or aluminum whose surface is anodized, a conductive path 12 made of copper foil provided in an arbitrary shape on the substrate 11, and a heat sink fixed on the conductive path 12 with solder. 13, a power transistor 14 fixed on the heat sink 13, a groove 19 which is a feature of the present invention, and a sealing resin layer 15 covering the power transistor 14.

The power transistor 14 is fixed to the inside of the groove 19 of the heat sink 13 with solder, and a sealing resin layer 15 such as epoxy resin is applied to cover and protect the power transistor 14. At this time, the sealing resin layer 15
is also filled in the groove 19. As a result, since the groove 19 of the heat sink 13 has an inverted tapered surface, even if stress is applied to the sealing resin layer due to heat cycles, the inverted tapered surface returns to its shape, so the sealing resin Peeling of layers can be prevented.

(F) Effects of the Invention According to the present invention, there is an advantage that the reverse tapered surface 18 can be easily formed on the heat sink 13 by two press steps. If it is incorporated into a hybrid integrated circuit, a sealed structure for the power transistor 14 that is resistant to heat cycles can be realized.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view explaining a conventional hybrid integrated circuit, FIGS. 2 A, B, and C are cross-sectional views explaining the method of manufacturing the heat sink of the present invention, and FIG. 3 is a cross-sectional view of a hybrid integrated circuit using the heat sink of the present invention. FIG. 2 is a cross-sectional view illustrating a circuit. Explanation of the main figure numbers: 13 is a heat sink, 19 is a groove, and 18 is a reverse tapered surface.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a flat heat sink in which only a power element is fixed, and a sealing resin for sealing the power element is placed on the top surface, comprising: A heat sink characterized in that a groove is formed near the periphery to which the power element is fixed so as to surround the power element, and an inner end of the groove surrounding the power element is pressed to form a reverse tapered surface. Production method.