JPH07263475A - Protective resin casting mold - Google Patents

Abstract

PURPOSE:To prevent sagging of resin to a contact part with an electrode plate when protective resin is cast by airtightly holding an outer periphery of a semiconductor base via a cavity by upper and lower cases. CONSTITUTION:An upper cast mold 2 made of heat resistant resin and a lower cast mold 3 made of heat resistant resin are respectively assembled with upper and lower cases 4, 5. In this case, the molds 2, 3 form an airtight cavity 6 together with semiconductor base 1 when the base 1 is held. Two through holes 7, 8 are respectively provided at the case 4 and the mold 2 assembled with the case 4 to communicate with the cavity 6. Thus, the resin is not sagged out of the cavity at the time of casting the resin, and the resin can be formed on an outer periphery 21 of the base.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention does not fix a semiconductor substrate such as a diode, a reverse blocking three-terminal thyristor (SCR), a gate turn-off thyristor (GTO) and a reverse conduction type gate turn-off thyristor (RC-GTO) to a substrate. The present invention relates to a casting device for casting and forming a protective resin on the outer peripheral portion of a semiconductor substrate of an alloy-free flat semiconductor device in which electrode bodies are brought into pressure contact with both surfaces thereof.

[0002]

2. Description of the Related Art FIG. 4 is a diagram showing a conventional coating method for forming a protective resin on the outer peripheral portion of a semiconductor substrate. Disc-shaped semiconductor substrate 1 provided with an appropriately required PN junction structure
The formation of the protective resin 22 on the outer peripheral portion 21 of the semiconductor substrate, which is necessary to secure the reliability of the electrical characteristics such as the withstand voltage, has been conventionally performed by the coating method. Here, the semiconductor substrate 1 and the electrode plate 18
Since the structure is fixed by the brazing wax 23, the electrode plate 1
The semiconductor substrate 1 brazed to No. 8 was fixed to the rotary stage 19 and was rotated while applying the protective resin by the nozzle 17 located above or a brush or the like.

[0003]

In the method as described above, the application of the protective resin is a manual work, and since the protective resin is applied by the nozzle 17 or the brush, unevenness and bubbles are included in the application. There were cases. The presence of such unevenness and bubbles is extremely likely to lead to deterioration of electrical characteristics such as pressure resistance. Further, this method is possible when the semiconductor substrate 1 is fixed to the electrode plate 18 by brazing, but an assembly structure in which the semiconductor substrate 1 and the electrode plate 18 are simply joined by pressure contact without brazing. In this case, it is necessary to mount the thin semiconductor substrate alone on the rotary stage and apply the protective resin. In this case, in addition to unevenness and inclusion of air bubbles, the applied protective resin drips to the contact surface between the semiconductor substrate and the electrode plate, and when the semiconductor substrate is sandwiched between the electrode plates and pressure-contacted, the semiconductor substrate is damaged. There is a fear.

In view of the above problems, the object of the present invention is to prevent brazing, that is, to secure the reliability of the electrical characteristics of the alloy-free type flat semiconductor device, and further when the semiconductor substrate and the electrode plate are brought into pressure contact with each other. It is an object of the present invention to provide a protective resin casting device for preventing the positional deviation from the above and the semiconductor substrate from being damaged.

[0005]

According to the present invention, a protective resin casting apparatus for forming a protective resin on the outer peripheral portion of a disk-shaped semiconductor substrate keeps the semiconductor substrate airtight according to the present invention. An upper case and a lower case that are sandwiched in this way are provided, and an upper casting mold that forms an annular airtight cavity inside each of the upper and lower cases so as to face each other at a position where a protective resin is formed on the outer peripheral portion of the semiconductor substrate. Part and lower casting part are respectively incorporated, and at least two or more through holes communicating from the outside of the case to the cavity are provided in the case and the casting part, respectively. Further, it is effective that each of the upper casting part and the lower casting part is made of a heat-resistant resin having a temperature of 250 ° C. or higher. Further, at least one first O-ring is arranged between each of the upper and lower cases and the upper and lower casting parts incorporated in the case, and the first O-ring arranged in the upper case. It is also effective to arrange the first O-ring and the first O-ring arranged in the lower case so as to face each other through the casting part, and the lower casting part is located outside the cavity formed in the casting part. It is also effective to dispose a second O-ring on the contact surface between the mold and the upper casting part.

[0006]

In the above-mentioned device, the outer case of the semiconductor substrate is kept airtight by the cavity by the upper case and the lower case, so that when the protective resin is injected, the resin is prevented from dripping into the contact portion with the electrode plate. be able to. In addition, by providing two or more through holes, it is possible to secure a place where air in the cavity escapes in addition to the place where the protective resin is injected. The thickness of the semiconductor substrate may differ depending on the model (for example, GTO and diode), and even if the semiconductor model is the same, variation in thickness is unavoidable. Therefore, even if the semiconductor substrate is thinner than the design dimension of the protective resin casting device, at least one first O-ring is provided between the upper and lower cases and the upper and lower casting parts incorporated in the case. And the first O-ring arranged in the upper case and the first O-ring arranged in the lower case are arranged so as to face each other with the casting section interposed therebetween. Since pressure is applied to the contacting portion by the first O-ring, the airtightness of the cavity can be reliably maintained. Further, when the thickness of the semiconductor substrate is thicker than the designed size, a gap is created in the contact portion between the upper and lower casting parts outside the cavity, but the second O-ring should be placed outside the cavity in the lower casting part. By the second O
A ring can close this gap and maintain airtightness.
Further, when the heat resistant resin having a heat resistant temperature of 250 ° C. or higher is used, the hardening temperature of the protective resin when the protective resin is hardened is usually 150 to 250 ° C., but this temperature deteriorates the heat resistant resin. There is nothing to do.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a sectional view of an embodiment of an apparatus for casting a protective resin on the outer periphery of a semiconductor substrate. The upper casting part 2 made of heat resistant resin and the lower casting part 3 made of heat resistant resin are
The upper casting part 2 and the lower casting part 3 are respectively assembled, and the upper casting part 2 and the lower casting part 3 form an airtight cavity 6 together with the semiconductor substrate 1 when the semiconductor substrate 1 is sandwiched. By forming the airtight cavity 6 in the outer peripheral portion of the semiconductor substrate with the heat-resistant resin in this manner, the protective resin can be formed in the outer peripheral portion 21 of the semiconductor substrate without the protective resin dripping outside the cavity when the protective resin is injected. Further, the upper case 4 and the upper casting portion 2 incorporated therein are provided with two through holes 7 and 8 communicating with the cavity 6 in advance.

Here, as the heat resistant resin, for example, a fluorine resin is used. Further, since the fluorine-based resin has excellent releasability, it can be easily taken out from the casting device after the protective resin is cast and cured. For the upper and lower cases, for example, Al or stainless steel can be used. FIG. 2 shows the embodiment of FIG. 1 in which an O-ring is further installed.
The same parts as those in FIG. 1 are designated by the same reference numerals. An annular groove for arranging the first O-ring 10 is provided between the upper case 4 and the upper casting part 2 and between the lower case 5 and the lower casting part 3, respectively, and the first O-ring 10 is arranged. Furthermore, an annular groove for arranging the first O-ring 9 is provided on the outer periphery of the lower casting part 3 and the first O-ring 9 is arranged. In the protective resin casting apparatus shown in FIG. 1 in which the O-ring is not arranged, when the protective resin is cast on the outer peripheral portion of the thin semiconductor substrate due to the variation in the thickness of the semiconductor substrate, the outer periphery of the semiconductor substrate There is a case where the contact portion 24 between the casting portion and the casting portion does not come into contact with each other and the airtightness of the cavity 6 cannot be ensured. However, when the first O-ring 10 is arranged, even if the thickness of the semiconductor substrate 1 is small, the first The O-ring 10 is made of heat-resistant resin 2,
The contact between 3 and the semiconductor substrate 1 is maintained. Also, the second O
The ring 9 prevents the formation of a gap between the contact portions 25 of the upper and lower casting parts outside the cavity when the semiconductor substrate 1 is thick. Therefore, since the second O-ring 9 may come into direct contact with the protective resin, the second O-ring 9 is coated with, for example, a fluorine-based resin in consideration of the peelability when the semiconductor substrate 1 is taken out from the device. Further, heat-resistant rubber is used for the O-rings 9 and 10 so that the air-tightness of the cavity is maintained and that it does not deteriorate due to the temperature when the protective resin is cured.

FIG. 3 is a block diagram showing a casting method using the protective resin casting apparatus shown in FIGS. 1 and 2, and the apparatus 13 is the protective resin casting apparatus shown in FIG. 1 or 2. .
The method of casting protective resin is to close the valve 12 and close the valve 14.
Is opened and the vacuum pump 16 is operated to remove the air in the cavity 6 for casting the protective resin of the protective resin casting device. With the vacuum pump 16 still operating, the valve 12 is opened to inject the protective resin into the cavity 6. Protective resin is tank 15
When it comes out, the vacuum pump 16 is stopped. Next, the valves 12 and 14 are closed to complete the casting of the protective resin. After this, the protective resin casting device 13 is removed and moved to the protective resin curing step. Since the airtightness of the cavity 6 into which the protective resin is cast can be sufficiently maintained, the protective resin is cast after the cavity 6 is evacuated to prevent unevenness and inclusion of air bubbles and prevent deterioration of pressure resistance. be able to.

[0010]

According to the present invention, the object of the present invention is to protect the semiconductor substrate or to position the semiconductor substrate and the electrode plate in an alloy-free type flat semiconductor device having a structure in which the semiconductor substrate and the electrode plate are not fixed by brazing. The protective resin casting device is composed of an upper case and a lower case for sandwiching the semiconductor substrate, and the semiconductor substrate is sandwiched between the upper and lower cases facing the portions corresponding to the outer periphery of the semiconductor substrate, and the semiconductor is formed on the outer periphery of the semiconductor substrate. By incorporating an upper casting part and a lower casting part made of heat-resistant resin that form an annular cavity with the base body and providing through holes in the upper case, it is possible to achieve airtightness during casting and to prevent unevenness and bubbles. It is possible to prevent inclusion and sagging, thereby preventing deterioration of electrical characteristics such as withstand voltage and preventing damage when the semiconductor substrate is sandwiched by electrode plates. That.

[Brief description of drawings]

FIG. 1 is a sectional view of a protective resin casting device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a protective resin casting device according to another embodiment of the present invention.

FIG. 3 is a configuration diagram showing an embodiment of a protective resin casting method of the present invention.

FIG. 4 is a diagram showing a method of applying a protective resin by a conventional method.

[Explanation of symbols]

 1 Semiconductor Base 2 Upper Casting Part 3 Lower Casting Part 4 Upper Case 5 Lower Case 6 Cavity 9 Outer O-ring 10 O-ring 18 Electrode Plate 22 Protective Resin

Claims (4)

[Claims] 1. A protective resin casting apparatus for forming a protective resin on the outer peripheral portion of a disk-shaped semiconductor substrate, comprising an upper case and a lower case for sandwiching the semiconductor substrate while keeping it airtight. Inside the upper and lower cases, an upper casting part and a lower casting part, which face each other at positions where a protective resin is to be formed on the outer peripheral portion of the semiconductor substrate and form an airtight cavity, are incorporated respectively. A protective resin casting device, characterized in that at least two through-holes are provided in each of the mold parts from the outside of the case to the cavity. 2. The protective resin casting apparatus according to claim 1, wherein the upper casting portion and the lower casting portion are each formed of a heat resistant resin having a heat resistant temperature of 250 ° C. or higher. 3. A first O 2 is provided between the upper and lower cases and the upper and lower casting parts incorporated in these cases, respectively.
At least one ring is arranged, and the first O-ring arranged in the upper case and the first O-ring arranged in the lower case are arranged so as to face each other via the casting part. The protective resin casting device according to claim 1 or 2. 4. The protective resin casting device according to claim 1, wherein a second O-ring is arranged on the contact surface between the lower casting portion and the upper casting portion outside the cavity.