JPH0341980B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a mold, and more particularly, to improvement of a gate in a lower die of a mold for producing a resin-sealed semiconductor device.

(2) Background of the technology Resin-encapsulated semiconductor devices (also called plastic ICs) are manufactured using a lead frame partially shown in Figure 1a, in which 1 is a lead frame, 2 is 3 indicates a pilot hole, 4 indicates a pinch, and 5 indicates a molded package. The lead frame 1 is placed on the lower mold shown in FIG.
After that, it is poured into the cavity. In other words, the runner 11 is a path through which the resin flows, and the gate 12
is an inlet for mold resin into the mold package 5.

Fig. 1b shows a cross section of a part of a mold for resin sealing, 13 is an upper mold, 14 is a lower mold, and 15 is a cavity. Rinne no Moldpackage 5
is formed.

In conventional molds, the gate 12 is located on one side of the illustrated mold package 5 off the longitudinal centerline. The reason for this configuration is that when the resin is cured in an overlapping relationship on the pinch 4, the mold package 5 is partially destroyed (cracked) and a notch is created in the process of cutting the pinch 4, and the gate is This is because the notch digs into the mold package cage during the break, or the gate break is not completed completely. Note that gate breaking refers to removing the resin that protrudes from the mold package in the shape of a gate.

(3) Prior art and problems Since the conventional gate position is deviated from the center line of the mold package as described above, the flow of resin into the cavity is poor, resulting in unfilled areas of resin and pins inside the mold package. Holes (formed by air bubbles), voids, etc. occur,
Instances have been experienced that have caused product defects.

(4) Purpose of the Invention In view of the above-mentioned conventional problems, the present invention provides a mold for manufacturing a resin-sealed semiconductor device, in which a gate serving as a resin inflow port is designed to prevent the resin from impeding the flow of the resin. The purpose is to reduce the defective rate of molded packages.

(5) Structure of the Invention According to the present invention, in the lower mold of the mold, the gate, which is the inlet for the mold resin, is connected to the cavity over the entire width of the cavity in which the mold package is formed. It is set at approximately the same depth as , and is open before resin injection.
We provide a mold in which a shutter is movably attached to the lower mold in two stages and closes with a small gap left between it and the lower side of the lead frame placed above the lower mold after the resin injection is completed. This is achieved by doing.

(6) Examples of the invention Examples of the invention will be described in detail below with reference to the drawings.

An embodiment of the invention is shown in plan view in FIG. 2a and in cross-section in FIG. 2b, in which the same reference numerals as in FIG.

Referring to FIG. 2a, 21 indicates a runner similar to the runner of FIG. 1, and 22 indicates a gate according to the invention. The gate 22 is provided over the entire width of the cavity 23 (in other words, the width of the mold package) and at approximately the same depth as the cavity. With such a configuration of the gate, the molten resin flows into the cavity 23 without any hindrance, so that the incidence of unfilling, pinholes, voids, etc. is significantly reduced.

A shutter 24 is provided at a portion of the gate in contact with the cavity 23. Referring to FIG. 2b, 25 is a groove in which the shutter 24 can slide in the direction of the arrow, 26 is a lower die, 27 is an ejector plate,
28 indicates an ejector pin, and the shutter 24
is attached to an ejector plate 27 to which an ejector pin 28 is attached. Ejector plate 27 and ejector pin 28
is built into a conventional molding die, and is configured so that as the ejector plate 27 moves upward, the ejector pin 28 protrudes the mold package 5. Since its configuration and operation are well known, detailed explanation will be omitted.

Prior to resin injection, the shutter 24 is placed so that its tip is flush with the bottom surface of the cavity 23. Immediately after resin injection is completed, the ejector plate 27 rises and stops at a position where the tip of the shutter 24 is approximately 0.1 mm below the bottom surface of the lead frame. The reason why there is a gap between the bottom surface of the lead frame and the tip of the shutter is to apply resin sealing (transfer) pressure to the entire cavity until the mold resin hardens. This is to keep the resin in the cavity and the resin in contact with each other (not disconnected). By doing so, the resin in the runner and the resin in the cavity are equally subjected to pressure from the plunger (not shown).

When the resin hardens, the ejector plate 27
is further raised, and the mold package 5 is pushed up using the ejector pin 28. At this time, play means for the shutter is provided on the ejector plate so that the shutter 24 does not move. The ejector plate has a two-step upward movement as described above, which can be achieved by modifying the ejector rod operation of the press, which is the conventional means for lifting the ejector plate. It has been confirmed that the resin that has entered the above-mentioned gap of about 0.1 mm does not cause the conventional problems such as notches in the mold package or cracks during pinch cutting in gate breaks.

(7) Effects of the Invention As explained above in detail, in the mold according to the present invention, by forming the gate to have the same width and depth as the cavity, the resin can smoothly flow into the cavity. realized without any hindrance,
It prevents unfilling, pinholes, bonds, etc. from occurring in the mold package, dramatically reduces the incidence of defective products, and prevents damage to the mold package caused by conventional gate breaks, making it easier to manufacture plastic ICs. This is highly effective in improving yield.

[Brief explanation of drawings]

1A and 1B are a plan view and a sectional view of a cavity portion of a conventional mold, and FIGS. 2A and 2B are a plan view and a sectional view of a cavity portion of a mold according to the present invention. 1...Lead frame, 5...Mold package, 21...Runner, 22...Gate, 23
... Cavity, 24... Shyatsuta, 25...
Groove, 26... lower die, 27... ejector plate, 28... ejector pin.

Claims (1)

[Claims] 1. A lower mold equipped with a cavity in which a mold package of a resin-sealed semiconductor device is molded, a runner for flowing resin into the cavity, and a gate provided between the runner and the cavity and serving as an inlet for resin into the cavity. In the molding die, the gate is formed to have the same width over the entire width of the cavity and the same depth as the cavity, and a shutter is provided at a portion of the gate in contact with the cavity, and this shutter is used before resin injection. 1. A molding die having a structure in which the molding die is opened, and after resin injection, the molding die is closed leaving a gap between the lead frame and the lead frame disposed on the lower die.