JPS6352457B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a method for manufacturing resin-sealed electronic components. When an electronic component, such as a lead frame on which a semiconductor pellet is mounted, is sealed with resin, a transfer injection molding method is sometimes used. The mold used for this molding method is generally a two-part mold consisting of an upper mold and a lower mold, and as shown in the example in Figure 1, a pot 1' runner 2' (multiple runners extending radially from the pot ), a gate 3', and a cavity 4' (a plurality of cavities are provided in one runner via each gate). In order to seal electronic components with resin, as shown in FIG. 1, a thermosetting resin tablet is loaded into a pot, an electronic component is set in each cavity, and the tablet is inserted into a plunger while the mold is heated. Pressure is applied at (5' in FIG. 1) and the tablets are transferred to each cavity via the runner and gate. During this transfer, the resin progresses in hardening, and the resin that reaches the inside of the cavity is moderately hardened. Therefore, when the cavity is filled with resin, the resin in the cavity has been hardened while the runner is moving and has become sufficiently hard, but the resin remaining in the runner has not yet hardened much. It is soft because it has not progressed. However, when the cavity is filled with resin, the descent of the plunger is stopped by the reaction force from the resin, generating high pressure.
This high pressure acts on the resin in the runner, the resin in the cavity, etc., and in this case, the resin in the runner is soft as described above, so
The occurrence of burrs is noticeable as they penetrate into the cracks of the mold. The occurrence of burrs on the runner is also facilitated by the fact that the runner is closer to the plunger than the cavity, and a higher pressure acts on the runner when fluid pressure loss is taken into account. However, the occurrence of such burrs on the runner makes it difficult to remove the residual resin from the runner after the mold is opened, which lengthens one molding cycle time, resulting in a decrease in workability. The method for manufacturing resin-sealed electronic components according to the present invention is a method that can reduce the occurrence of burrs on the runners, etc. described above, and includes loading a thermosetting resin tablet into a pot of a mold, and A method for manufacturing a resin-sealed electronic component, in which an electronic component is set in a cavity, the tablet loaded in the pot is transferred to the cavity via a runner and a gate under pressure from a plunger, and the resin is cured during this transfer. This method is characterized in that the upper part of the resin tablet has a faster curing time that takes less time than the lower part. The present invention will be explained below with reference to the drawings. In FIG. 2A, T indicates a thermosetting resin tablet, in which a powder of a composition containing a thermosetting resin such as an epoxy resin, a curing agent, a filler, a coloring agent, an internal mold release agent, etc. is mixed into a circle. It is cold formed into a columnar shape. As described above, this tablet is loaded into a pot of a mold, pressurized by a plunger, and transferred from the lower end of the pot to a cavity via a runner and a gate. In this case, the part that reaches the lower end of the tablet is transferred first, so when the resin reaches the cavity and the cavity is filled with resin, the resin in the cavity is occupied by the resin from the lower part of the tablet. The resin remaining at the bottom of the pot is occupied by the top of the tablet. This relationship is illustrated in FIG. 2A, where the vertical axis indicates the position of the passage. On the other hand, as mentioned above, the longer the path transfer time, the greater the amount of heat applied to the resin from the mold. Therefore, the closer the resin is to the cavity, the more heat it receives. It will look like Figure B. The vertical axis shows the position of the passage, and the horizontal axis shows the amount of heat. Therefore, if the composition of the thermosetting composition is the same, the degree of curing will increase as the amount of heat increases.
Therefore, if the composition of the tablet is the same over the entire length, the resin in the cavity will progress to hardness and be hard, causing burrs to form under pressure (transmission of plunger pressure) (to cracks in the mold). As mentioned above, the degree of curing of the resin in the runner is small and the hardness is low, making it impossible to avoid the occurrence of burrs. The purpose of the present invention is to alleviate such problems,
Under the heat-receiving conditions shown in Figure 2B, in order to make the degree of hardening of the resin in the runner as similar as possible to the degree of hardening of the resin in the cavity, the closer the resin is to the runner, the more the resin is hardened. Therefore, the upper part of the tablet should have a faster curing composition with a shorter curing time. Ideally, the amount of curing accelerator added or the type of curing accelerator should be varied in the longitudinal direction of the tablet in accordance with the change in the amount of heat received, but in this case, It is very difficult to mold the tablet into a tablet, so it is difficult to form the tablet into several layers, for example, three layers as shown in Figure 3A (the thickness ratio is higher than the upper layer).
_T1 : middle layer _T2 : lower layer _T3 = 1:1:2), upper layer
The curing time for the upper layer T ₁ is made shorter by increasing the amount of the curing accelerator or using a fast-reacting curing accelerator for the upper layer T ₁ . Even when using the two-layer structure (layer thickness is the same) as shown in Figure 3B, compared to the conventional example (single layer), the generation of burrs on the runner described above can be sufficiently reduced, making it easier to manufacture the tablet. Considering this, this two-layer structure is advantageous. In this case, for the lower layer Ta, that is, the part that requires longer curing time, use one with a gelling time of 70 to 90 seconds at a temperature of 150°C, and for the upper layer Tb, the gelling time is 0.4 of the lower layer gelling time. ~0.7 (however, within the range of 30 to 65 seconds) is desirable. Example The following formulation (parts are parts by weight) was kneaded for 5 minutes with a hot roll at 120°C, cooled and then ground to obtain a powder composition of 10 mesh passes, in a two-layer format at a pressure of 70 Kg/cm ² Compressed into tablets: height 80mm, diameter 55mm, weight 150g
A cylindrical two-layer tablet was obtained.

【table】

[Table] On the other hand, a single-layer tablet was obtained using a composition having the same composition as the lower layer composition and having the same dimensions and molding pressure as above. When semiconductors were encapsulated by transfer injection molding using this single-layer tablet and the above-mentioned two-layer tablet according to the embodiment of the present invention, it was observed that burrs were generated on the runner when the single-layer tablet was used. No such burrs were observed when using a double-layer tablet. In addition, the composition of the residual resin in the runner is the same as that of the mold resin in the cavity, including thermosetting resin, filler, colorant, internal mold release agent, etc., and the hardness and mold release properties of the residual resin in the runner are the same. Since it is in good condition with almost no difference from the molded resin body in the cavity, the residual resin body in the runner can be easily released from the mold in the same way as the molded resin body in the cavity. As described above, according to the method for manufacturing a resin-sealed electronic component according to the present invention, it is possible to prevent the occurrence of burrs on the runner in the transfer injection molding method, and it is possible to easily and reliably remove residual resin, thereby reducing the work time. You can improve your sexuality.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing a known transfer injection molding method for resin-sealed electronic components, and Figs. 2A and 2B show a conventional tablet used in the transfer injection molding method and the tablet. The explanatory diagram showing the heat receiving state, FIG. 3A and FIG. 3B are explanatory diagrams each showing the tablet used in the present invention. In the figure, T1 and Tb are the upper part of the tablet.

Claims (1)

[Claims] 1. Load a thermosetting resin tablet into a pot of a mold, set an electronic component in a cavity of the same mold, and transfer the tablet loaded into the pot to the cavity via a runner and a gate by pressure from a plunger, In the method for manufacturing resin-sealed electronic components in which the resin is cured during this transfer, the composition of the thermosetting resin, filler, colorant, internal mold release agent, etc. in the upper and lower parts of the resin tablet is determined. A resin characterized in that it has a fast curing property with a short curing time by using a larger amount of curing accelerator in the upper part than in the lower part, or by using a fast-reacting curing accelerator. A method for manufacturing sealed electronic components.