JPS5839868Y2 - Resin sealing mold - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to improvement of resin sealing molds.

There are various conventional resin encapsulation methods such as casting and transfer, and among these, the transfer resin encapsulation method is generally adopted as a method for encapsulating semiconductor devices due to its mass productivity and workability. There is.

In the manufacture of resin-sealed semiconductor devices, there is a step of molding circuit elements fixed to a lead frame, wires connecting the circuit elements and external leads, etc. with resin.

What is used at this time is a resin sealing mold (hereinafter abbreviated as the mold), which is formed by an upper mold and a lower mold, and the semiconductor element to be resin-sealed is placed in the gear body, which is a space. The lead frame attached to the semiconductor element is held in such a way that the semiconductor element is incorporated therein.

To seal with resin, a thermosetting resin is placed in the chamber of the upper mold, the plunger is lowered to press the resin, the resin enters the cull of the lower mold, and is softened by the preheated mold.
Transferred through a runner, resin is injected under pressure into a plurality of cavities through a gate.

Thereafter, the resin is cured, and the upper and lower molds are opened to take out the resin-sealed semiconductor device.

When sealing with resin, if the time it takes to fill a cavity with resin differs depending on the cavity, the resin that is filled into the cavity faster will harden earlier, so it may be difficult to cure the resin while there are still cavities that are not completely filled. This means that there is a cavity, and the resin in that cavity hardens without being sufficiently loaded with the holding pressure of the injection plunger.

Therefore, the air bubbles contained in the resin remain without being fully removed from the air vent, and semiconductor devices sealed with resin in this state have poor moisture resistance, resulting in variations. .

When a large number of semiconductor devices are encapsulated with resin in this way, if they are not encapsulated in the same way, there will be variations and the above-mentioned problems will occur, so it is necessary to prevent such problems. Various measures are being taken to do so.

For example, the cross-sectional shape of the runner through which the resin is transferred is made constant, and the sprue is formed so that the length of the flow path of the runner is as equal as possible, so that the mold is equipped with a branch runner.
Various types of molds have been devised, such as molds in which the direction of the sub-runner connected to the runner is at an obtuse angle with respect to the extending direction of the runner to improve the flow of resin into the cavity.

However, in the former case, the length of the runner becomes longer, so the injection pressure must be increased, which makes the product more likely to be glued, and since the sprue is provided, the structure of the mold becomes complicated, which is not economical.

In the latter case, the variation in resin filling time between the cavities on both sides of the runner will be reduced, but the variation in the filling time from the cull will still remain, and the resin filling time for each cavity will be uniform. The condition is still not available.

In any case, it is difficult to keep the resin filling time constant for each cavity, which causes variations in the characteristics of the resin-sealed semiconductor device, deteriorates the electrical characteristics, and makes the semiconductor device defective. There was a drawback that some things were put away.

The present invention was developed to eliminate these drawbacks, and improves the quality of resin-sealed products by improving the shape of the mold so that each cavity is filled with resin almost simultaneously. The purpose of the present invention is to provide a mold that can be resin-sealed at low cost.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the lower mold of the mold of the present invention. 1 is a cull into which the resin is placed, and a plurality of runners 2 through which the resin flows from the cull 1 are formed symmetrically around the cull 1 (four in this figure), and each runner 2 has a plurality of cavities. A resin sealing portion consisting of 3 is formed.

That is, this resin sealing part is formed with a pair of cavities 3, 3 facing each other on both sides of each runner 2, and a structure in which the pair of cavities 3, 3 are spaced apart with a part of the runner 2 interposed therebetween. ing.

The four runners formed symmetrically from the cull have the same cross-sectional area and the same length up to the nearest cavity 3.

The groove width of the runner 2 thus formed is constant, and the groove depth is formed to become shallower as the distance from the cull 1 increases.

That is, the groove becomes shallow near the entrance of the first cavity of the runner in FIG. 1, and continues to become shallower at a constant rate until it reaches the end point of the runner.

An outline is shown in Figure 2. The same goes for the other three runners.

Also, a cavity 3 formed connected to the runner 2
The length and depth of the gate 4 at the entrance of the runner are the same whether it is near or far from the cull, but the gate width, that is, the width in the direction perpendicular to the direction in which the resin flows through the runner, is larger than that near the cull. Those farther away from Cal are formed larger.

The width of C in FIG. 1 is smaller than the width of d.

The same holds true for the gate widths of the other three runners.

Since the runner and gate are shaped as shown above, when the resin is softened and pushed out by the plunger and filled into the cavity from the cull through the runner and gate, a portion of the resin flows through the runner. enters the cavity through the gate. Conventionally, the cross section of the runner was uniform, so the flow rate of the resin slowed down as it moved away from the cull, but in this invention, the depth became shallower as it moved away from the cull. The flow rate of the resin increases as it moves away from the cull, and the gate width of the cavity that is far from the cull is larger, making it easier for resin to flow into the cavities and filling each cavity with resin. This makes it possible to keep the resin filling time constant until the resin filling is completed.

In this way, when the mold of the present invention is used, the resin fills all the cavities almost simultaneously, and there are fewer microvoids in resin-sealed semiconductor devices, for example. Since the holding pressure applied is uniform, air bubbles in the resin are easily defoamed, and product characteristics can be improved without variation.

Furthermore, the mold is easy to process, and the length of the runner does not have to be particularly long, so the resin used can be used to eliminate waste, making it economical.

In addition to what is shown in the drawings above, in accordance with the gist of the present invention, the cross-sectional shape of the runner may be narrowed not only in depth but also in width at a certain rate, and the gate may also be narrowed not only in width but also in length. Alternatively, the cross-sectional area may be increased by varying the distance from the cull.

The above explanation has been made using a resin-sealed semiconductor device as an example, but it goes without saying that the application is not limited to this and can also be applied to other resin-sealed products, and the molds are not limited to those shown. Of course, a modified structure can be obtained according to the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 is a plan view of an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the runner shown in FIG. 1 taken along line A--A. 1... Cal, 2... Runner, 3...
...Cavity, 4...Gate.

Claims (1)

[Scope of utility model registration request] A resin seal consisting of a cull, a plurality of runners extending symmetrically from the cull around the cull, and a plurality of cavities formed on the plurality of runners through a part of the runner and a gate, respectively. each runner between the cull and the cavity closest to the cull is formed to have the same cross-sectional area and the same length, and the runner between the plurality of cavities on each runner has a depth. The cavity is shallower from the cavity closest to the cull to the next cavity, and the width of the gate is wider in the cavity farther from the cull than in the gate closer to the cull. Resin sealing mold.