JPH0213141Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a resin molding device for resin molding electronic parts and the like.

Conventional technology Resin molding of resin mold type semiconductor devices is generally performed on multiple lead frames at the same time by clamping multiple lead frames that have undergone pellet mounting and wire bonding using upper and lower molds. . For example, an example of a resin molded transistor is shown in FIGS. 4 and 5. 1 is a lead frame formed by integrally molding a plurality of sets of three lead parts 2; 3 is a lead frame made of a plurality of lead parts 2; The pellet of the transistor mounted at the pellet mount position, 4 is a wire connecting the pellet 3 and the required lead of lead part 2, 5 is each lead part 2
This is an exterior resin material that is resin-molded on the main part including the pellets 3. A specific example of an apparatus for resin molding the lead frame 1 after wire bonding will be explained below with reference to FIGS. 6 to 11.

In FIGS. 6 and 7, 6 and 7 are a pair of upper and lower molds for resin molding.
The upper mold 6 has a circular pot 8 in the center that penetrates the upper and lower surfaces, and a plurality of runners 9 extending from the bottom peripheral surface of the pot 8 are provided at the abutting portion of the upper and lower molds 6 and 7.
A plurality of gates 1 extending laterally from each runner 9
0 and a plurality of cavities 11 communicating with the tip opening of each gate 10 are formed. The upper and lower molds 6 and 7 in this drawing are for mold-clamping a total of eight lead frames 1 and molding them by resin molding, and the resin molding is performed as follows.

Eight lead frames 1 are positioned and placed on a lower mold 7 so that their molded portions to be resin enter the cavity 11, and the upper and lower molds 6 and 7 are clamped. Both molds 6 and 7 are heated, and a quantity of preheated resin tablet 12 is put into pot 8 as shown in FIG. 8, and is pressed from above by plunger 13. Then resin tablet 12
is pressurized and melted, and the molten resin material 12' is injected from the pot 8 through the runner 9 and the gate 10 into the cavity 11 by the pressing force of the plunger 13, and the plunger 13 releases the resin material 12' into the pot 8 as shown in FIG. When the resin has descended to near the bottom of the cavity 11, filling of the resin into the entire cavity 11 is completed.

Incidentally, in such a resin molding apparatus, a resin stopper for blocking the flow of the molten resin material is selectively fitted to the root portion of the runner 9 as appropriate for the following reason.

If the runner 9, gate 10, cavity 11, etc. are damaged due to partial chipping, etc., there will be a subtle change in the injection conditions of the molten resin material into the cavity 11 corresponding to the damaged part, and as a result, the filling resin may be insufficiently filled. Resin mold defects such as air bubbles may occur. Therefore, in order to prevent this type of defective product from occurring, a resin stopper 14 having a trapezoidal cross section as shown in FIG. I'm here. For example, if the resin stopper 14 is fitted and fixed to one of the four runners 9, the pot 8 will contain enough resin tablets 12 to fill the cavities 11 communicating with the remaining three runners 9 with molten resin. The molten resin material 12' is poured into the runner 9 where the resin stopper 14 is placed, and as shown in FIG. Therefore, the occurrence of defective resin molded products is prevented.

In addition, the upper and lower molds 6 and 7 in Fig. 6 are used for a total of 8 molds at one time.
Although one lead frame 1 is resin molded, in some cases it may be desired to reduce the number of lead frames 1 to 6 or 4 at a time. Therefore, in such a case, a resin stopper 14 is fixed to the runner 9 which is not used, and the necessary amount of resin tablets 12 is put into the pot 8 to perform resin molding.

Problems to be Solved by the Invention The conventional resin stopper 14 described above is selectively fixed to the runner 9 with an adhesive 15, but the adhesive 15 is subject to thermal expansion and contraction during repeated resin molding operations. As a result of repeated thermal and mechanical stress, the adhesive strength of the resin stopper 14 becomes weak, and during molding, the resin stopper 14 moves from its normal position due to the pressing force of the molten resin material 12', causing the resin stopper 14 to become damaged. The amount of resin injected into other runners 9 without runners 14 was less than the normal amount, and as a result, defective resin molded products sometimes occurred due to insufficient resin filling. Also, such a resin stopper 1
When the adhesive 15 was moved, the adhesive 15 sometimes oozed out and stained the mold.

Furthermore, the resin stopper 14 is removed from the runner 9 when a defect on the mold side is repaired, or when eight lead frames 1 are to be resin-molded at once in the mold shown in FIG. Removal was performed by peeling the adhesive 15 from the runner 9 using a release agent, which was a cumbersome and time-consuming process.

Means for solving the problems This invention was proposed in view of the above problems.
The above problem is solved by forming the resin stopper with a permanent magnet.

Function The resin stopper of the permanent magnet mentioned above is fixed by magnetic adsorption to a part of the mold runner, so it is easy to attach and remove the resin stopper, and there is a problem that the mold gets dirty with adhesive. will be completely eliminated. In addition, since the resin stopper of the permanent magnet is sufficiently strongly magnetically attracted to the bottom surface of the runner, there is no need to worry about the position shifting due to the pressing force of the molten resin material injected into the runner, and good resin molding can always be performed.

Embodiment An embodiment in which the present invention is applied to a resin molding device having upper and lower molds 6 and 7 in FIG. 6 will be described below based on FIGS. 1 and 2. The only difference is that a resin stopper 16 is formed of a permanent magnet to be selectively fitted and fixed to the root portion of 9 as necessary.

This permanent magnet resin stopper 16 has the same cross-sectional shape as the runner 9, and when fitted into a part of the root portion of the runner 9, it completely comes into close contact with the bottom surface of the runner 9 and is magnetically attracted. Resin stopper of such a permanent magnet 1
Since the resin stopper 6 is stably fixed in a fixed position on the runner 9 without being affected by thermal expansion and contraction due to repeated resin molding operations, the resin stopper 16 always satisfactorily achieves its purpose. Also, resin stopper 16
When removing the runner from the runner 9, it can be easily done by inserting a sharp tool between the resin stopper 16 and the bottom of the runner 9.

In FIG. 3, a permanent magnet plate 17 that is flush with the bottom surface is fixed in advance to a part of the bottom surface of the runner 9, and a resin stopper 16 is fixed onto this permanent magnet plate 17 as necessary. be. In this case, runner 9
It is sufficient to magnetize the permanent magnet plate 17 and the resin stopper 16 in the length direction and integrate them with different magnetic poles.In this case, to remove the resin stopper 16, place the resin stopper 16 on the permanent magnet plate 17. This can be done more easily by sliding the magnetic poles a little along the same axis, bringing the same magnetic poles of the two closer together so that they repel each other.

Note that the present invention is not limited to resin molding devices for semiconductor devices such as transistors.

Effects of the invention Since the present invention uses a permanent magnet for the resin stopper that is appropriately fitted to the runner of the mold, the adhesion of the resin stopper to the runner is stable and good resin molding can always be carried out. Further, since the resin stopper is magnetically attracted to the runner, it is easy to attach and detach the resin stopper, and it is possible to provide good responsiveness to changes in the number of resin-molded parts to be resin-molded at one time.

[Brief explanation of the drawing]

FIG. 1 is a partial plan view showing an embodiment of the present invention;
FIG. 2 is an enlarged cross-sectional view taken along the line A--A in FIG. 1, and FIG. 3 is a cross-sectional view of main parts showing another embodiment of the present invention. 4 and 5 are a plan view and a sectional view taken along the line B-B showing an example of a resin molded product, and FIGS. 6 and 7 are a plan view and an enlarged sectional view taken along the line C-C of a conventional resin molding device. , and FIGS. 8 to 11 are cross-sectional views of the portion shown in FIG. 7 in various operating states. 6, 7...Mold, 8...Pot, 9...Runner, 16...Resin stopper of permanent magnet.

Claims (1)

[Scope of utility model registration request] A resin molding device characterized in that a resin stopper made of a permanent magnet is removably fitted to a part of a runner extending from a pot of a mold for resin molding.