JPH0339218Y2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Technical Field of the Invention The present invention relates to a transfer molding apparatus used for mode molding, for example, resin-sealed semiconductor devices.

(2) Background of the Technology Taking the molding of a resin-sealed semiconductor device as an example, it is manufactured using a lead frame partially shown in FIG. 1 (partially shown by broken lines). In the figure, 1 is a lead frame placed on a lower die of a mold die (described later), 2 is a cradle, 3 is a pilot hole, 4 is a pinch, 5 is a mold package, and 6 is a lead.

The mold package 5 is molded using a mold, and the process involves placing the lead frame 1, on which the chip 8 is mounted and wire bonding has been completed, in a cavity (described later) provided in the mold, and This is done by applying pressure to a pellet (molten thermosetting resin) and pouring it into the cavity through the runner 11 and gate 12 of the lower mold (mold press). After the mold package 5 is molded, it is separated from the lead frame 1 and the leads are deformed into a predetermined shape to complete the resin-sealed semiconductor device 7 shown in FIG. 2.

FIG. 3 is a schematic cross-sectional view of a transfer molding device that performs the resin sealing.
1 is a mold consisting of an upper mold 14 and a lower mold 15.
2 is a runner, 13 is a cavity, 16 is a cull that receives the molten resin, 17 is an injection plunger that applies pressure to the resin pellet 18 (hereinafter simply referred to as resin), and 19 is a pot in which the injection plunger 18 moves up and down. shows. In FIG. 3, only three cavities 13 are shown for the sake of simplicity, but in reality, from several tens to over a hundred cavities are provided in the mold.

In such a molding device, the resin 18 is heated to about 180 degrees by the heat from the mold 10;
The injection plunger 18 is melted by the pressure caused by being lowered by a drive device (for example, a hydraulic device) not shown, and the molten resin passes through the cull 16, the runner 12, and then the gate (not shown) into the cavity 13. sent. When the molten resin is fed into all the cavities 13, the injection plunger 17 returns upward and one stroke is completed.

(3) Problems with the prior art The dropping pressure of the injection plunger 17 is, for example, 60 kg/cm ² so that the molten resin is completely fed.
However, it has been experienced that the pressure of the resin is not maintained at a predetermined value due to, for example, leakage of molten resin into the gap between the injection plunger 17 and the inner wall of the pot, resulting in various problems. .

FIG. 4 is a schematic sectional view of the main part of the transfer molding apparatus including the injection plunger 17. Referring to the figure, there is a slight gap between the injection plunger 17 and the bottle 19 (exaggerated in the figure). be). Therefore, when the injection plunger 17 descends to apply pressure to the molten resin, the resin also enters the void, resulting in a pressure drop.

Conventionally, in order to prevent the pressure drop, two grooves 22a and 22b are provided on the outer circumference of the injection plunger 17.
has been established. Because there are 22a and 22b,
The resin that has entered the gap first stays in the lower groove 22a and fills the groove 22a. Since the resin is thermosetting, after the stroke is completed, it cools and hardens and adheres tightly to the wall of the pot 19, creating a state similar to that of an O-ring. The thermosetting resin material thus formed is prevented from leaking during subsequent strokes by the O-ring portion 21a. Note that if resin leakage cannot be sufficiently prevented by using only the groove 22a, replace the upper groove 2 in the same manner as in the case of the groove 22a.
2b is also formed with an O-ring portion 21b to prevent resin leakage.

By providing the two grooves 22a and 22b described above in the injection plunger 17, it is possible to prevent resin leakage by having a double seal hardening. It has been confirmed that the pressure applied to the resin 21 of the injection plunger 17 is reduced due to the friction between the injection plunger 21a, 21b and the wall surface of the bottle 19. If the pressure of the resin 21 decreases in this way, the resin will not be injected into the cavity 13 sufficiently, causing air bubbles to get inside the mold package 5 of the resin-sealed semiconductor device 7 shown in FIG. Otherwise, chips may occur, causing defects. However, in a conventional mold press, the injection plunger 1
The pressure applied to 7 is kept constant at 60Kg/ ^cm2 ,
Although the pressure is monitored to ensure that there are no fluctuations in the value, the pressure actually applied to the resin 21 is not monitored, so it is not possible to reliably compensate for the pressure reduced due to friction. There is a drawback that it is not possible to completely prevent the occurrence of defective products due to the above-mentioned lack of pressure.

(4) Purpose of the invention In view of the above-mentioned conventional problems, the object of the present invention is to provide a transfer molding device that can monitor the pressure drop due to friction and apply the correct pressure to the molten resin.

(5) Structure of the invention According to the invention, in a mold press that performs transfer molding,
A pressure-sensitive element is provided on the surface of the injection plunger or cull that contacts the resin through a thin wall plate to detect the pressure of the thermosetting resin in the mold, and the pressure sensor detects the pressure detected by the pressure-sensitive element. This is achieved by a transfer molding apparatus characterized in that it is configured to control the injection pressure of the resin.

(6) Example of implementation of the idea Hereinafter, embodiments of the present invention will be explained in detail with reference to the drawings.

FIG. 5 is a schematic sectional view of a main part of a transfer molding apparatus including an injection plunger for explaining an embodiment of the present invention.

Referring to the figure, an injection plunger 23 has a cylindrical cavity 24 inside an injection plunger 23 which has two grooves 21a and 21b around it, similar in appearance to the conventional one.
form. This cylindrical cavity 24 penetrates through the center of the injection plunger 23, and its tip surface is separated by a small thickness from a surface 27 of the plunger 23 that contacts the molten resin 21 (hereinafter, this surface will be referred to as a single surface 27). form up to a certain point. This thickness is appropriately set within the range of 0.5 mm to 1.0 mm depending on the dimensions of the plunger 23 and the pressure to be applied to the resin.

Next, at the tip of the cavity 24, a pressure sensing element 25 and a conversion device 26 for converting the pressure change of the pressure sensing element 25 into an electric signal and taking it out are arranged, and the conversion result is used for pressure control (not shown) through a wiring 28. input into the device. For example, strain gauges are used as pressure-sensitive elements.
gage).

In the injection plunger 23 having such a configuration,
The portion of the surface 27 of the injection plunger 23 in which the pressure sensitive element 25 is disposed is thin and easily deforms when pressurized. This deformation is the cavity 2
After being detected by the pressure sensitive element 25 inside 4,
It is immediately converted into an electrical signal and sent to the control device.
As a result, the actual pressure value actually applied to the molten resin 21 during the pressurizing operation can be detected by the pressure sensing element 2 through the thin wall plate.
5, the pressure inside the mold press can always be detected with high sensitivity without deteriorating the pressure detection accuracy due to the hardened resin adhering to the pressure sensitive element 25. Therefore, the injection plunger is adjusted according to this detected pressure. The injection pressure can be corrected to apply the correct pressure to the resin.

Thus, the O formed in the grooves 22a and 22b
Regardless of the amount of friction between the ring portions 21a and 21b and the wall of the pot 19, it is ensured that accurate pressure is applied to the resin.

The transfer molding apparatus of the present invention described above is not only used for manufacturing resin-sealed semiconductor devices, but can also be applied to any apparatus that performs molding operations using metal molds and the like. Note that by arranging the pressure sensitive element under the bottom surface of the cull 12 (indicated by reference numeral 29 in the figure) instead of inside the injection plunger 23, and by reducing the thickness of the bottom surface, the pressure of the resin can be applied directly. can be detected, and the purpose of the present invention can be achieved. On the other hand, the arrangement of the pressure detection means in the injection plunger 23 can be easily carried out by conventional techniques.

(7) Effects of the invention As explained in detail above, according to the invention, it is possible to provide a transfer molding device that can apply accurate pressure to the resin regardless of the friction between the injection plunger and the bottle, resulting in stable molding. This is highly effective in reducing the occurrence of defective mold packages in the manufacture of resin-sealed semiconductor devices, for example, and in improving manufacturing yields and reliability of semiconductor devices.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a lead frame placed in a cavity, Fig. 2 is a perspective view of a resin-sealed semiconductor device, Fig. 3 is a schematic sectional view of a transfer molding machine, and Fig. 4 is a conventional FIG. 5 is a diagram for explaining the transfer molding apparatus according to the embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Lead frame, 5... Mold package, 7... Resin-sealed semiconductor device, 11... Runner, 12... Gate, 13... Cavity,
14... Upper mold, 15... Lower mold, 16... Cal, 1
7, 23...Injection plunger, 19...Bottle, 22a, 22b...Groove, 24...Cavity, 25
...Pressure sensitive element.

Claims (1)

[Claim for Utility Model Registration] In a mold press that performs transfer molding, the pressure of the thermosetting resin in the mold is detected through a thin wall plate on the surface of the injection plunger or cull that is in contact with the resin. 1. A transfer molding apparatus comprising a pressure sensitive element and configured to control the injection pressure of the resin in accordance with the pressure detected by the pressure sensitive element.