JPH03206629A - Metal mold for semiconductor resin-sealing - Google Patents

Abstract

PURPOSE:To reduce that a sink on the surface of a package and a void at the inside are produced by a method wherein an air vent is formed as a three- layer structure or it is formed in a position which is symmetric with respect to a gate by using a semiconductor element as the center and the residual air remaining inside a cavity of a metal mold is reduced as far as possible at a resin injection operation. CONSTITUTION:Main metal molds 1a, 1b, a partitioning block 3 and a lead frame 4 are sandwiched and pressurized as shown in the crosssectional view at a resin injection operation; a molten resin 11 is injected into a lower metal- mold cavity and an upper metal-mold cavity 2a, 2b from a subrunner 6. At this time, the resin 11 which is injected forcibly is shaped in such a way that the tip is collapsed inside the cavities. An air layer 10 is left inside the upper metal-mold cavity 2b; it is discharged from an air vent 7 formed on the surface of the partitioning block 3 and is reduced to be very small. The resin 11 is filled completely into the lower metal-mold and upper metal mold cavities 2a, 2b and the resin-injection operation is finished. Thereby, it is possible to sharply reduce that a sink on the surface of a package and a void at the inside are produced in a molded product.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a mold for sealing a semiconductor integrated circuit element (hereinafter referred to as IC) with a resin, and in particular to a mold for sealing an optical element with a transparent resin. The present invention relates to a semiconductor resin encapsulation mold for molding.

[Conventional technology]

Conventionally, this type of mold for semiconductor resin encapsulation has air exhaust holes (hereinafter referred to as An air vent 7) is located at an arbitrary position on the side opposite to the side where the resin injection port (hereinafter referred to as gate) is located.
Upper and lower molds 1b in contact with the top and bottom surfaces of the lead frame 4. It was formed only on the surface of 1a. Also,
When the semiconductor element 5 to be encapsulated is an optical element, the melt viscosity of the transparent resin used is approximately 300 poise, which is higher than the approximately 200 poise of ordinary IC encapsulation resin. In order to prevent the bonding wire from flowing, the injection speed was approximately half that of the normal injection speed. [Problems to be Solved by the Invention] In the conventional semiconductor resin encapsulation mold described above, air vents are formed only on the surface that contacts the lead frame.
In addition, in order to prevent wire deformation during resin injection, it is necessary to slow down the resin injection speed, and it usually takes 10 minutes from the time the resin begins to flow into the ■ cavities until they are completely filled.
It was more than a second ago.

In such a case, the resin forced into the cavity by the injection cylinder for resin injection flows as shown in the resin 11 shown in Fig. 5 when it passes through the cavity from the gatero and reaches the opposite side. mold cavity 2
The air JWIO trapped in b loses its exhaust hole and eventually appears as voids or sink marks on the external appearance of the IC, which is one of the causes of failure.

Particularly for optical semiconductors, such voids and sink marks have caused problems, such as diffuse reflection and refraction of light, which have a direct negative effect on optical properties.

The conventional mold for semiconductor resin encapsulation described above has air vents only on the surfaces of the upper mold and lower mold that contact the lead frame, whereas the present invention has air vents on the side surface of the cavity part of the upper mold. A portion forming a part of the block is divided into a divided structure, and an air vent is also provided in a portion corresponding to the height of the upper surface of the upper mold cavity portion of the divided block. By doing so, the present sealing mold can be used on the bottom surface of the lead frame, the top surface of the lead frame,
The difference is that it has three layers of air vents on the top surface of the package.

Another difference is that the air vent is located on an extension line connecting the center point of the gate width of the resin injection gate and the center point of the semiconductor element mounted on the lead frame.

[Means to solve the problem]

The semiconductor resin encapsulation mold of the present invention includes a lower mold, an upper mold, and a divided block sandwiched between the lower mold and the upper mold. The lower mold is formed with runners, sub-runners, and gates that serve as flow paths for the resin, a cavity that forms the package, and air vents that discharge air from these recessed spaces. The cavity is shaped in the part facing the lower mold cavity. The divided blocks have air vents on the top and bottom surfaces similar to those of the lower mold, and are fixed in position by guide bins of the lower mold.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is an exploded perspective view of Embodiment 1 of the present invention. ]a is the lower mold, lb is the upper mold, and 3 is the divided block. The lower mold 1a includes a runner and a sub-runner 6 (not shown), a lower mold cavity 2a which becomes a lower package, and a depth of 5 μm.
In addition, a lead frame guide bin 8a for fixing the lead frame 4 and a guide bin 9a for fixing the divided block 3 are respectively implanted. The upper mold 1b is formed with an upper mold cavity 2b for a portion that will become the upper package of the IC, and a guide bin relief hole 9C. And divided block 3
Air vents 7 with a depth of approximately 5 μm are installed on the top and bottom surfaces.
A guide hole 9b and a lead frame guide bin relief hole 8c are respectively penetrated therethrough.

The molds 1a, lb, the divided blocks 3, and the lead frame 4 are clamped and pressurized as shown in the cross-sectional view of the functional parts of the first embodiment in FIG. is injected into the lower and upper mold cavities 2a and 2b. At that time, the resin 11 that was forcibly injected as described above has a shape in which the tip collapses inside the cavity, and the air layer 10 remains in the upper die cavity 2b, but the resin 11 is not formed on the upper surface of the divided block 3. The resin 11 is discharged from the air vent 7, and the resin 11 is filled into both the lower and upper mold cavities 2a and 2b, and the resin injection is completed.

Next, a second embodiment of the present invention will be described. In this embodiment, the position of the air vent is set based on certain conditions, and will be explained using the package plan view of FIG. 3. First, point A is the center point 12 of the gate width defined on one side of the package 15. Further, the midpoint 13 of the semiconductor element 5 mounted on the lead frame is defined as a point B, and an extension line connecting points A and B is assumed. In such a case, the intersection of the extended line and the other side of the package 15 is set as a point C, and an air vent having a predetermined width centered at the point C is formed.

Normally, in this type of resin encapsulation of semiconductor devices, the molten resin injected from the gate advances through the cavity during the resin inflow process and is filled. Since the flow resistance of the resin is greater than that of other parts, the advancing speed is slow, and the molten resin exhibits a flow form like the resin boundary line 16 shown in FIG. 3. In this case, the resin reaches the slowest point at a position symmetrical to the gate around point B of the midpoint 13 of the semiconductor element, and providing an air vent at that position is effective in reducing defects such as voids.

However, it goes without saying that this embodiment can be used in combination with a three-layer air vent similar to that of embodiment 1 to achieve even greater effects. There is nothing wrong with providing additional information.

〔Effect of the invention〕

As explained above, the present invention minimizes the amount of air remaining in the mold cavity during resin injection by forming the air vent into a three-layer structure or by providing it in a position symmetrical to the gate with the semiconductor element in the center. be able to. Therefore, it is possible to significantly reduce the occurrence of sink marks on the package surface, voids, etc. inside the package in the packaged product.

This is a significant quality improvement, especially in optical elements, where even the smallest bubbles or dust can cause deterioration in sensitivity.

[Brief explanation of drawings]

Fig. 1 is an exploded perspective view of Embodiment 1 of the present invention, Fig. 2 is a sectional view of functional parts of Embodiment 1, Fig. 3 is a plan view of the package of Embodiment 2 of the present invention, and Fig. 4 is a conventional metal Exploded perspective view of the mold, No. 5
The figure is a sectional view of a functional part of a conventional mold. 1a...Lower mold, 1b...Upper mold, 2a...Lower mold cavity, 2b...Upper mold cavity, 3...Divided block, 4...Lead frame, 5... Semiconductor element, 6... Sub-runner 7... Air vent, 8
a...Lead frame guide bin, 8b...Lead frame guide hole, 8C...Lead frame guide pin escape hole, 9a...Guide bin, 9b...Guide hole, 9c...Guide pin escape hole Hole, 10...air layer, 1
DESCRIPTION OF SYMBOLS 1... Resin, 12... Gate center point, l3... Semiconductor element center point, 14... Air vent center point, 15...
...Package, 16...Resin boundary line.

Claims (1)

[Scope of Claims] 1. In a pair of upper and lower semiconductor resin sealing molds for resin-sealing a semiconductor element mounted on a lead frame after bonding with a thin metal wire, a vent hole for air discharge in a cavity portion. A mold for semiconductor resin encapsulation, characterized in that: is provided at a location located at the same height as the top surface of an upper mold cavity. 2. The mold for semiconductor resin encapsulation according to claim 1, wherein the air discharge hole of the cavity portion is provided at a location of the upper mold cavity located on an extension line connecting at least the center of the resin injection port and the center of the semiconductor element. Type.