JPH04157761A - Cutting method for tie bar - Google Patents

Abstract

PURPOSE:To cut a tie bar without generating a resin residue by irradiating a resin dam with a laser light ray from a generation source of a YAG or CO2, melting to remove the resin of the dam by heat, and then cutting to remove the bar by using a punch and a die. CONSTITUTION:A resin dam 3 is irradiated with a laser light ray 1 in a large area at each about 0.1mm of width at a periphery of the dam 3. About 50mum of thickness of the resin therein is removed though a lead frame 2 therearound is not changed at all in the dam 3 irradiated with the ray 1. This is repeated three to four times at each one position to remove all the resin. Then, a tie bar 5 is removed by a punch 4. The punch 4 is pectinated, and can simultaneously cut the bar 5 at a plurality of positions. A lead shape after the resin of the dam 3 and the bar 5 are removed has no resin residue in the dam 3 to complete cutting of the bar.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for cutting tie bars in the manufacturing process of resin-molded semiconductor devices (hereinafter referred to as molded ICs), and particularly relates to a method for cutting tie bars in the manufacturing process of resin-sealed semiconductor devices (hereinafter referred to as molded ICs), and particularly relates to a method for cutting tie bars in the manufacturing process of resin-sealed semiconductor devices (hereinafter referred to as molded ICs). The present invention relates to a tie bar cutting method for removing resin from a tie bar and a resin dam part.

[Conventional technology]

Conventionally, this type of tie bar cutting method is as shown in Fig. 3(a), (
As shown in the explanation sections b) and (c), using a punch set in the press mold and a die that precisely fits into the punch, mold resin is molded as shown in Fig. 3 (a>). This is a method of simultaneously punching out the resin dam part 3 and tie bar part 5 that are produced between the leads of the lead frame 2 coming out from the lead frame 9, and this method uses a plurality of punches 7 as shown in FIG. 3(b). A common method was to arrange the resin dam part and the tie bar part in a comb-like shape to match the positions of the resin dam part and the tie bar part, and punch out the resin dam part and the tie bar part at a plurality of locations at the same time.

There are two methods for arranging punches in a comb-teeth pattern: a method in which punches are arranged one by one in a row, and a method in which a plurality of punches are processed simultaneously from one material and then arranged. In the tie bar part after punching, a resin residual part 8 is generated around the resin dam part due to the clearance, as shown in FIG. 3(C).

[Problem to be solved by the invention]

The conventional tie bar cutting method described above is a mechanical punching method using a punch and die, and takes into account manufacturing tolerances of the punch and die, misalignment of the resin sealing of the molded IC, tolerances of the lead frame, etc. Considering punching, when punching out the resin dam portion, residual resin parts with a thickness of about 0.1 mm are generated on the left and right lead sides and the mold resin side, respectively.

This residual resin is only caught between the leads and may fall off in the next process. It has the disadvantage that it can cause bites and scratches, which can cause damage to the punch or die in the mold. Furthermore, if there is a residual resin, the plating that will be applied in the next step will not adhere to the side surface of the resin dam portion of the lead, and the lead will not be protected.

In contrast to the conventional tie bar cutting method described above, the tie bar cutting method of the present invention uses a laser beam such as a YAG laser or a CO2 laser to remove the resin from the resin dam part, and irradiates the laser beam to an area larger than the resin dam part. The difference is that all the resin in the resin dam part is melted and removed so as not to generate residual resin, and then the tie bar part is cut using a punch and die.

[Means to solve the problem]

The tie bar cutting method of the present invention involves irradiating a resin dam with a laser beam whose source is YAG or C02, melting and removing the resin in the dam with the heat, and then cutting the tie bar using a punch and die. This is a method of removing it.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIGS. 1(a), (b), and (c) are explanatory diagrams of Embodiment 1 of the present invention. The laser beam 1 is generated from YAG or C02, and the irradiation area is larger than the resin dam part 3 by about 0.1 mm in width around the periphery.

The irradiation energy is not strong enough to cut the lead frame 2, but is about several W/cm 2 , and a thickness of about 50 μm of resin can be removed with one irradiation.

The irradiation method involves focusing the laser beam using a lens or the like to match the desired irradiation area, and guiding the laser beam to the desired resin dam portion using a mirror or the like and irradiating the laser beam. The number of irradiations is about 3 to 4 times, since the thickness of the resin that can be removed by one irradiation is about 50 μm. The lead frame 2 is made of 42 alloy or copper, and its thickness ranges from 0-15mm to 0.5mm.
It is about 2 mm. The resin that has flowed into the resin dam portion 3 is the same material as the resin sealing the molded IC, and has the same thickness as the lead frame 2. The punch 4 is made of cemented carbide, and the length is long enough to cut only the tie bar portion 5, and the width is about 0.1 mm on both sides from the width of the tie bar to prevent it from digging into the lead during cutting. It's narrow.

The laser beam 1 is irradiated on the resin dam part 3 one by one in an area larger than the resin dam part 3 by about 0.1 mm in width as shown in FIG. 1 (a).The resin dam irradiated with the laser beam 1 In section 3, the surrounding lead frame 2 does not change at all, but only the resin inside is removed to a thickness of about 50 μm.By repeating this about 3 to 4 times per 1 meter section,
Remove only the resin. Next, as shown in FIG. 1<b>, the tie bar portion 5 is removed with a punch 4. In addition, punch 4
It has a comb tooth shape, and the tie bar portion 5 can be cut at multiple locations at the same time. Resin of resin dam part 3 and tie bar part 5
After the lead shape is removed, as shown in FIG. 1(c), the tie bar cutting is completed with no resin remaining in the resin dam portion 3.

FIG. 2 is an explanatory diagram of Embodiment 2 of the present invention. The laser beam 6 uses YAG or CO2 as the source as in Example 1, but its irradiation area is wide so that multiple resin dam parts 3 can be irradiated simultaneously, as shown in FIG. 2, and the depth direction is wide. 0.1 mm toward the main body side of the mold resin 9 as in Example 1
, the path is about 0.1 mm into the tie bar portion 5 side.

Irradiation energy and number of irradiations are the same as in Example 1.

When laser beams 6 are irradiated to multiple resin dam portions 3 at the same time, the laser beams 6 that hit the lead frame 2 are reflected, but the laser beams 6 that hit the resin dam portions 3 hit the resin at one time.
A thickness of approximately 50 μm is removed in each step. This is repeated 3 to 4 times to remove the resin with a thickness of 150 μm to 200 μm. The subsequent cutting of the tie bar portion 5 is the same as in the first embodiment. In this second embodiment, since the resin dam portions at a plurality of locations are irradiated with the laser beam at the same time, there is an advantage that the irradiation time of the laser beam can be shortened.

〔Effect of the invention〕

As described above, the present invention has the advantage that by using a laser beam to remove resin from the resin dam portion, tie bar cutting can be performed without generating resin residue.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of Embodiment 1 of the present invention, where Figure (a) shows the irradiation position of the laser beam, Figure (b) shows the tie bar cutting position, and Figure (C) shows the tie bar after cutting. Figure 2 is an explanatory diagram of the second embodiment of the present invention, Figure 3 is a diagram showing the shape of the lead.
The figure is an explanatory diagram of the conventional tie bar cutting method. Figure (a) shows the resin dam part, Figure (b) shows the tie bar cutting position, and Figure (c) shows the shape of the lead after the tie bar is cut. FIG. 1... Laser beam, 2... Lead frame, 3...
・Resin dam part, 4... punch, 5... tie bar part,
6... Laser beam, 7... Punch, 8... Resin remainder, 9... Mold resin.

Claims (1)

[Claims] In the tie bar cutting method, in which the resin dam part and the tie bar part are cut and removed at the same time after resin sealing, the resin dam part is irradiated with a laser beam, the heat melts the resin in the dam part and removed, and then a punch is used to remove the resin. A tie bar cutting method characterized by cutting and removing a tie bar portion using a method.