JPH0222995Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to resin molded semiconductor devices such as transistors.

Conventional technology A resin molded semiconductor device has a semiconductor pellet fixed on the main surface of a substrate (heat sink), and a lead placed near the substrate and a surface electrode of the semiconductor pellet.
The general structure is that electrical connections are made using wires such as Al wires, and the main parts of the substrate, including the area around which the pellets are fixed, are molded and covered with a resin material. The moisture resistance of this resin-molded semiconductor device is almost determined by the adhesion between the outer resin material and the metal surfaces of the substrate and leads, and is particularly greatly influenced by the adhesion between the outer resin material and the substrate.

By the way, when partially sealing a metal substrate with resin, the molded exterior resin material shrinks in volume due to the difference in thermal expansion coefficient between the resin and the metal, resulting in poor adhesion to the substrate. In order to prevent surface oxidation, the surface of the board is plated with nickel plating, etc., but it is difficult for the resin to adhere to the plating layer on the surface, resulting in poor adhesion between the board and the exterior resin material. This has made it difficult to improve the moisture resistance of resin-molded semiconductor devices.

Therefore, in order to extend the time for external moisture that enters the interface between the exterior resin material and the substrate to reach the semiconductor pellet, the moisture-resistant life can be extended and the moisture resistance can be substantially improved. Forming a groove to lengthen the entry path as much as possible is practiced in transistors and the like. A specific example thereof will be explained below based on the transistors shown in FIGS. 7 and 8.

In FIGS. 7 and 8, 1 is a heat sink which is a semiconductor pellet fixed substrate, 2 is a set of three leads extending from the vicinity of the heat sink 1, and the tip of the central one is caulked to the heat sink 1. It is integrated with. 3 is a semiconductor pellet of a transistor fixed on the main surface of the heat sink 1 with solder 4; 5 is a semiconductor pellet 3;
A wire such as an Al wire electrically connects the surface electrode with the two tips on both sides of the lead 2, and 6 is an exterior resin material that is resin-molded on the main part of the heat sink 1, including the area around the pellet fixing part. . Reference numeral 7 denotes a mounting hole formed in a portion m of the heat sink 1 that protrudes from the exterior resin material 6.

A feature of this transistor is that a groove 8 is formed across the heat sink 1 at a location close to the heat sink protruding portion m on the resin molded portion n of the main surface of the heat sink 1 on the pellet-fixing side. When the groove 8 is formed in this way, external moisture that enters from the interface between the exterior resin material 6 and the heat sink protruding portion m reaches the groove 8 and then passes through a curved path toward the side, bottom, and side surfaces of the groove 8. The semiconductor pellet 3 has to be directed toward the semiconductor pellet 3, and the time it takes to reach the semiconductor pellet 3 is delayed by the time it takes to cross the groove 8, which lengthens the moisture-resistant life. Furthermore, the adhesion strength of the exterior resin material 6 increases as the exterior resin material 6 bites into the groove 8, thereby stably maintaining the adhesion between the exterior resin material 6 and the heat sink 1, and improving moisture resistance.

Problems to be Solved by the Invention The groove 8 prevents external moisture from entering and delays the time for it to reach the semiconductor pellet 3, but the time required for the external moisture to cross the groove 8 is longer than the groove 8. There was no significant difference in the time required for external moisture to penetrate a width corresponding to the width of the groove 8, and therefore, the groove 8 could not be expected to have much of an effect in preventing intrusion of external moisture. Furthermore, the exterior resin material 6 bites into the groove 8, but this biting force is weak in the thickness direction of the heat sink 1 and is not effective in keeping the exterior resin material 6 tightly attached to the main surface of the heat sink 1. However, little improvement in moisture resistance can be expected from such a biting structure, and further improvement measures have been desired.

Means for Solving the Problems The present invention was developed in view of the above-mentioned needs, and consists of a strip that forms a minute gap with the substrate and is fixedly arranged on the resin molded part of the main surface of the substrate to which the semiconductor pellet is fixed. By doing so, the above-mentioned conventional problems are solved.

Effect When the strip is fixedly arranged on the substrate with a minute gap as in the present invention, external moisture that enters toward the strip from the interface between the fixed substrate and the molded exterior resin material is fixed to the strip. Enters the micro space between the substrates,
In this space, moisture migrates to the end of the strip due to capillary action, then enters the interface between the exterior resin material and the substrate again, and a portion of it heads toward the semiconductor pellet, until the invading moisture reaches the semiconductor pellet. This significantly increases the moisture resistance, resulting in a substantial improvement in moisture resistance. In addition, since the resin slightly bites into the space between the strip and the board, the adhesion strength of the exterior resin material in the board thickness direction can be sufficiently increased, and the adhesion of the exterior resin material is stable and moisture resistance is further improved. things can be provided.

Embodiment An embodiment in which the present invention is applied to the resin-molded transistor shown in FIG. 7 will be described below with reference to FIGS. 1 to 4. The same parts as in FIG. Explanation will be omitted. The difference is that a strip, e.g., a long strip 10 made of heat-resistant hard material such as metal or ceramic, is placed at a fixed point on the resin-molded portion n of the main surface of the heat sink 9 on the side where the semiconductor pellets are fixed, and a small gap g is placed between the heat sink 9 and the heat sink 9. However, it was placed in a fixed position.

The strip plate 10 is attached to the heat sink 9 at a location close to the heat sink protruding portion m on the resin molded portion n of the main surface of the heat sink 9.
A heat dissipation plate 9 of this length is arranged to cross the
The gap g between the molten resin and the strip plate 1 during resin molding is
The size is set so that a minute space 11 is created between the strip plate 10 and the heat sink plate 9 after resin molding by biting in slightly below zero (for example, 20 μm or less). Furthermore, a single groove 12 similar to the conventional one is formed in the portion of the heat dissipation plate 9 facing the strip plate 10 to more reliably regulate the flow direction of external moisture, but this groove 12 is not necessarily required. The strip plate 10 can be attached by, for example, partially protruding stepped embossing 13 on the heat dissipation plate 9 and drilling mounting holes 14 partially in the strip plate 10, as shown in FIG. , the emboss 13 is fitted into the mounting hole 14 and the emboss 13 protrudes from the mounting hole 14.
This is done by crushing the tip of the holder onto the band plate 10.

In the above embodiment, external moisture entering the interface between the molded exterior resin material 6 and the main surface of the heat sink 9 from the heat sink protruding portion m advances in the direction of the broken line arrow in FIG. That is, it first reaches below the strip plate 10 and enters the minute space 11 formed under the strip plate 10. Moisture that has entered the microspace 11 flows in the longitudinal direction of the strip 10 due to capillary action, reaches below both ends of the strip 10, and from there enters the interface between the side surface of the heat sink 9 and the exterior resin material 6, and some moisture advances onto the main surface of the heat sink 9 and eventually reaches the portion where the semiconductor pellet is fixed. The path for this moisture to reach the part where the semiconductor pellet is fixed is much longer than that of the conventional product shown in FIG. The time it takes to reach the desired temperature is several times longer, and the moisture resistance is improved accordingly.

Furthermore, since the exterior resin material 6 is molded in such a way that it slightly protrudes below the periphery of the lower surface of the band plate 10, the exterior resin material 6 can be molded with the back surface of the heat sink 9 exposed on the non-semiconductor pellet side. The fixing strength of the heat dissipating plate 9 is strong and stable, good density is maintained, and even better moisture resistance can be provided.

It should be noted that the present invention is not limited to the above-mentioned embodiment, but also includes, for example, the fifth embodiment.
As shown in FIG. 6 and FIG. 6, a U-shaped band plate 10' surrounding the semiconductor pellet fixed part from three sides is fixedly arranged on the peripheral part of the resin molded part n of the main surface of the heat dissipation plate 9' with a small gap g. You may. When the U-shaped band plate 10' is used in this way, the path and time taken by external moisture to reach the part where the semiconductor pellet is fixed becomes longer.

In addition, this invention is not limited to transistors, but also SCR,
The present invention can be similarly applied to resin molded semiconductor devices such as ICs.

Effects of the invention According to the invention, even if the adhesion between the substrate and the molded exterior resin material is somewhat poor, the time it takes for external moisture that has entered the interface between the two to reach the semiconductor pellet is lengthened by the addition of the strips. Moisture resistance is substantially improved, and the adhesion strength of the exterior resin material to the substrate is increased by the addition of the stripes, making it possible to provide a product with even more stable moisture resistance.

[Brief explanation of the drawing]

Figure 1 is a plan view showing one embodiment of the present invention;
3 and 3 are an enlarged sectional view taken along the lines AA and BB in FIG. 1, FIG. 4 is a partially enlarged perspective view of the semiconductor device shown in FIG. 1, and FIG. FIG. 6 is an enlarged sectional view taken along the line C--C in FIG. 5. FIG. 7 is a plan view of a conventional resin molded semiconductor device, and FIG. 8 is a sectional view taken along the line DD in FIG. 7. 3... Semiconductor pellet, 6... Exterior resin material, n
... Resin molded part, 9, 9'... Substrate (heat sink), 10, 10'... Strip (band plate), 11...
Microspace, g...microgap.

Claims (1)

[Scope of utility model registration request] A semiconductor pellet is fixed to a substrate, its electrodes and leads are connected with a wire, and the main part including the semiconductor pellet is molded and covered with a resin material, in which the main surface of the substrate on the side to which the semiconductor pellet is fixed is A resin-sealed mold type semiconductor device, characterized in that a striped body forming a minute gap with respect to the substrate is fixedly arranged in the resin-covered portion.