JPH0513635A - Cutting method for tie bar - Google Patents

Abstract

PURPOSE:To prevent the deformation of external leads due to damage of them by detecting a tie bar or image recognition mark to find coordinates for laser irradiation, correcting the registered position to be irradiated by laser, and laser-cutting the tie bar. CONSTITUTION:A sealing resin 3 contracts in a sealing process, changing the lead pitch. After that the position of tie bars is detected. A TV camera 10 picks up image of a position recognition mark given on a lead frame 2 or tie bar 4 in a specific position, and the image is processed by a image recognition unit 11, position coordinates being detected. Then, the deviation from the position of laser irradiation stored is calculated, and the position coordinates for irradiation are corrected. A galvanometer 13 is operated according to the corrected data, irradiating a laser light 15 and cutting the tie bar 4 of the lead frame 2. This enables correcting the displacement of the tie bar 4 due to the contraction of the sealing resin 3, preventing damage to the external leads.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tie bar cutting method for cutting a tie bar of a resin-sealed semiconductor device, and more particularly to a tie bar cutting method for cutting a tie bar with a laser beam.

[0002]

2. Description of the Related Art Conventionally, a tie bar cutting method for cutting a tie bar of a resin-sealed semiconductor device (hereinafter referred to as an IC) by laser light is shown in FIG. 6 mounted on a laser irradiation stage as shown in FIG. After the positioning pin is inserted into the positioning hole 20 of the lead frame 2 to position the lead frame 2, the laser beam 15 is driven and deflected by driving the galvanometer 13 according to the laser irradiation position coordinates input in the program in advance, and the tie bar 4 is sequentially moved. It was irradiated and melted.

[0003]

In this conventional tie bar cutting method, the lead frame and the tie bar are positioned by inserting the positioning pin provided in the laser irradiation stage into the positioning hole provided in the lead frame, and the laser is cut. The light 15 is sequentially irradiated in accordance with the laser irradiation position coordinates input in the program in advance. The mutual positional relationship of the lead frame positioning hole tie bars is that the lead frame bends due to contraction of the sealing resin body after resin sealing,
Since swelling and lead pitch contraction occur and the individual lead frames and ICs change, a miniaturized and multi-pin IC with a fine lead pitch (0.5 mm or less) is designed for high-density board mounting. In the formed lead frame, as shown in FIG.
Deviates from the center line 19 of the tie bar and a part of the external lead 17 is lost, leading to lead bending and twisting in the lead forming process of the next process, which often causes non-standard defects of the lead forming shape to improve quality. It has the drawback of lowering it.

[0004]

The tie bar cutting method of the present invention detects a specific tie bar or a tie bar in order to detect the tie bar position after the encapsulating resin body shrinks and the lead pitch changes in the encapsulating step. The position of the position recognition mark provided in the vicinity is detected by the image recognition means, the deviation amount between the position information obtained by the image processing and the laser light irradiation position information registered in advance is calculated, and this position information is used as a variable. The position correction is performed using a fixed correction calculation expression described above, and the tie bar is cut by irradiating a laser beam based on the corrected result.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram for explaining one embodiment of the present invention, and FIG. 2 is a plan view of a lead frame used in the present invention.

As shown in FIGS. 1 and 2, the lead frame 2 fixed to the laser irradiation stage 1 is attached to the illumination lamp 2.
The image of the two position recognition marks 5a and 5b provided in the vicinity of the tie bar 4 on the diagonal of the lead frame 2 with respect to the encapsulating resin body 3 is illuminated by the large-diameter lens 6, the dichroic mirror 7, the half mirror. 8, imaging lens 9
The ITV camera 10 picks up an image through the image, and the image recognition unit 11 performs image processing to detect the accurate position coordinates of the marks 5a and 5b. The position coordinates of the detected marks 5a and 5b are transferred to the correction arithmetic unit 12, the deviation amount from the pre-programmed laser irradiation position coordinates is calculated, the accurate laser irradiation position is determined, and then the galvanometer 13 is driven. A laser beam 15 oscillated from a laser oscillator 14 is sequentially applied to the tie bars 4 to cut all the tie bars.

In this way, as shown in FIG. 3, even for an IC with a fine lead pitch of 0.5 mm or less, the deviation of the tie bar cutting is controlled to prevent damage to the external leads and to achieve stable cutting. It is possible to

As shown in FIG. 4, in addition to the marks 5a and 5b for position recognition, marks 5c and 5d are provided on the sealing resin body 3.
By providing four tie bars in the vicinity of the two diagonal lines, the position detection accuracy can be further improved and the amount of deviation can be accurately corrected. It is effective when the contraction of the lead pitch greatly affects the contraction.

Here, instead of detecting the position using the position recognition mark, the position may be detected from the image of the specific tie bar.

[0011]

As described above, according to the present invention, the laser irradiation position coordinates are accurately determined by detecting the tie bar or the image recognition mark provided in the vicinity of the tie bar, and the registered laser irradiation position coordinates are corrected. By performing the laser irradiation, it is possible to collectively perform tie bar cutting processing with stable laser light with little cutting deviation even for fine pitch ICs with a lead pitch of 0.5 mm or less. It is possible to prevent the external leads from being deformed due to the damage to the IC, and it is possible to obtain sufficient reliability even in the future miniaturization of IC and increase in the number of pins.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining an embodiment of the present invention.

FIG. 2 is a plan view of a first lead frame used in the present invention.

FIG. 3 is a partially enlarged view of a lead frame for explaining an embodiment of the present invention.

FIG. 4 is a plan view of a second lead frame used in an embodiment of the present invention.

FIG. 5 is a block diagram for explaining a conventional tie bar cutting method.

FIG. 6 is a plan view of a lead frame used in a conventional tie bar cutting method.

FIG. 7 is a partially enlarged view of a lead frame for explaining a conventional tie bar cutting method.

[Explanation of symbols]

1 Laser irradiation stage 2 lead frame 3 Sealing resin 4 tie bar 5a, 5b, 5c, 5d marks 6 large aperture lens 7 dichroic mirror 8 half mirror 9 Imaging lens 10 ITV camera 11 Image recognition unit 12 Correction calculation unit 13 Galvanometer 14 Laser oscillator 15 Laser light 16 Tie bar cutting area 17 External lead 18 Lead frame feed hole 19 tie bar center line 20 Positioning hole 21 Lighting lamp P lead pitch

Claims (2)

[Claims] 1. A tie bar cutting method for cutting a tie bar of a resin-encapsulated semiconductor device with a laser beam, wherein image recognition is performed on a position of a specific tie bar or a plurality of specific tie bars of a lead frame or a position recognition mark provided near the tie bar. Detected by the means, calculate the amount of deviation between the position information calculated by image processing and the laser light irradiation position information registered in advance, correct the laser light irradiation position information by the deviation amount, and based on the corrected result A method of cutting a tie bar, characterized in that the tie bar is cut by sequentially controlling laser light to irradiate the tie bar. 2. The tie bar cutting method according to claim 1, wherein a TV camera is used as the image recognition means.