JPH02260650A - chip carrier - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a chip carrier that uses a resin or ceramic envelope to pot semiconductor elements mounted with liquid resin.

(Prior art) A semiconductor element such as tCl or a transistor is mounted on a resin or ceramic envelope having mounting electrodes,
There is a chip carrier that is bonded by die bonding, then wire bonded with gold wire, etc., and then potted with a weather-resistant liquid epoxy resin with good adhesion.

(Problems to be Solved by the Invention) When this type of conventional chip carrier is soldered to a resin substrate having a circuit pattern, microscopic peeling occurs at the joint between the potting resin and the resin or ceramic envelope. The Wr-cut semiconductor element was damaged by crack components that entered through the microscopically peeled portions or by moisture from the atmosphere that occurred when left unused. That is, while epoxy resin potting resin has good adhesion to the chip carrier body and excellent mechanical properties,
Large coefficient of thermal expansion. For this reason, in order to prevent damage to semiconductor elements such as silicon due to thermal shock, a large amount of silicon oxide fine powder is added to the epoxy resin as a filler to reduce the coefficient of thermal expansion of the potting resin. However, when the potting resin is dropped onto a chip carrier on which a semiconductor element is mounted, the tip of the dropping of the potting resin has a low filler content and forms a structure containing a large amount of resin component, a resin-rich layer. As a result, the effect of suppressing the coefficient of thermal expansion is reduced, and microscopic peeling from the substrate is likely to occur due to the difference in the coefficient of thermal expansion from the small value range. When soldering a chip carrier with this structure to another circuit board, such as a PC board, using a flux, when the temperature rises, the vapor or liquid of activated components such as abietic acid is released using a rosin-based flux. There was a problem in that it invaded this peeled part and damaged the internal semiconductor element. FIG. 3 is an explanatory view of a conventional embodiment, and is an enlarged view of the tip of the potting resin. In the figure, 1 is the chip carrier, 5 is the potting resin, 5° is the resin component, and 5" is the silicon oxide fine powder filler. The added filler 5" is the surface tension of the resin, the particle size of the powder, the selection of the shape sample, etc. Although the resin is uniformly mixed in most of the region, only the resin with good fluidity at the end portions diffuses to the chip carrier surface by capillary action, forming a resin-rich layer 8 containing a large amount of resin component.

(Means for Solving the Problems) In order to solve these drawbacks, the present invention is characterized by configuring a layer in the chip carrier for suppressing the thin extension of the tip portion of the potting resin. The purpose is to increase the wetting angle at the tip of the potting resin to a certain value or more to prevent the occurrence of areas with low filler content, and to prevent thermal shock from occurring when attaching and soldering the chip carrier to the board. To provide a chip carrier that does not damage semiconductor elements even when exposed to flux components.

(Example) FIG. 1 is a detailed explanatory diagram of the present invention, and is a perspective view of a chip carrier on which a semiconductor element is mounted and resin is potted. In the figure, 1 is a chip carrier, 2 is a solder joint for attachment to an external circuit board, 3 is a semiconductor element, 4 is a bonding wire for wiring and bonding the semiconductor element to the chip carrier, 5 is a potting resin, and 6 is a potting resin. At the tip thereof, there is a convex portion of a dike made of, for example, silicone resin or fluorocarbon resin. FIG. 2 is a detailed explanatory diagram of the present invention, and is an enlarged view of the tip portion of the chip carrier joint portion of the potting resin 5 of FIG. 1. 7 is the wetting angle of the potting resin 5.

As described above, the semiconductor element 3 is coated with the potting resin 5 using a pressure dispenser or the like. At this time, potteng resin 5
In order to improve workability, for example, the resin and the chip carrier 1 are heated to several tens of degrees (generally from 40 to 55 degrees Celsius). In advance, the potting resin 5 is sufficiently stirred and mixed with the resin 5° and the filler 5'' using a jar roller or the like, and degassed under reduced pressure.Then, the potting resin 5 is coated with a semiconductor element 3 and a bonding wire such as a gold wire using a dispenser. Completely cover the chip carrier 1 with a resin such as fluorocarbon resin that has low wettability with epoxy resin and suppresses the outflow of the potting resin 5 within a narrow range by printing or transferring. 6. By configuring in this manner, a resin region with a low filler content at the tip portion of the potting resin 5 for bonding the chip carrier is eliminated.

As a result, the filler 5" is uniformly distributed throughout the potted resin coating, making it possible to obtain a value with little variation in the coefficient of thermal expansion in some parts, and a chip carrier that does not have microscopic cracks even when subjected to thermal shock. As an additional explanation, the effect of this convex portion can be obtained in circuits with high mounting density, such as chip carriers.Fine powder filler of silicon oxide is effective in suppressing the coefficient of thermal expansion. In the case of a potten resin whose content exceeds 25% in terms of specific gravity, if the wetting angle of the potten resin to the chip carrier is 45 degrees or more, the resin at the tip and the filler will not separate and it will not be possible to obtain the desired potten resin composition. I can do it.

The protrusions are created by printing the fluorocarbon resin on the chip carrier as described above, but in the case of small-scale applications, application with a brush is also possible. In addition, although a particularly remarkable effect is exhibited when the material of the chip carrier is made of a ceramic substrate such as aluminum oxide, which has a small coefficient of thermal expansion, the method according to the present invention can also obtain the same effect when using a resin-based material.

(Effects of the Invention) As explained above, in a chip carrier that uses an epoxy resin containing a filler as a potting resin, the wetting angle of the potting resin can be increased to 45° by the convex portion that is less likely to disturb the resin in the tip region of the potting resin. This has the advantage of being able to provide a chip carrier that does not cause microscopic cracks even during soldering when attaching the chip carrier to an external board because it prevents the formation of a resin rich layer where the filler and resin are separated. .

[Brief explanation of drawings]

FIG. 1 is a perspective view of a chip carrier according to an embodiment of the present invention, FIG. 2 is an enlarged view of the tip portion of the potting resin shown in FIG. 1, and FIG. 3 is an enlarged view of the conventional potting resin portion. 1...Chip carrier, 2...Solder joint part, 3.
...Semiconductor element, 4. Bonding wire, 5. Potting resin, 5°... Resin, 5. Filler 6.. Convex part, angle, 8. ... Resin wealthy class.

Claims (2)

[Claims] (1) In a chip carrier in which a semiconductor element is placed on a chip carrier having mounting electrodes and connected by bonding wires, and the semiconductor element and the bonding wires are potted with epoxy resin, an embankment is formed around the potted epoxy resin. A chip carrier characterized by having a convex portion. (2) A chip carrier characterized in that the epoxy resin according to claim 1 has a wetting angle on a substrate of 45 degrees or more.