JPH0286151A - Manufacture of lead frame - Google Patents

Abstract

PURPOSE:To uniformize etching quantity in a metal material sheet by a method wherein, at the time when etching is practically progressed half, the direction of metal material is changed by 90 deg., and execute the residual etching. CONSTITUTION:For example, photo resist is spread on metal material 2 and dried; a pattern of 100-pin lead frame whose lead pitch is 0.3mm is exposed and printed on the and front the rear thereof by ultra-high pressure mercury lamp light source; baking is performed after development using trichlorothylene. This metal material is carried in etching equipment 1 provided with a rocking injection nozzle 4 which jetts ferric chloride solution from the upper surface and the lower surface. Etching is performed for ten minutes; the direction of metal material is changed by 90 deg., and the material is again subjected to etching; the etching is continued until a desired dimension is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a method of manufacturing a lead frame with a narrow lead pitch by etching.

[Conventional technology]

Lead frame manufacturing methods include press punching and photo etching.

The general method of manufacturing lead frames by photoetching is to first apply photoresist to a metal material, and then
A photoresist film is formed by drying, the pattern is exposed to light on the photoresist film using a photomask with a desired lead frame pattern drawn thereon, and then developed to form a lead frame on the metal material. A photoresist film having a shape is formed, the metal material having a pattern formed with this photoresist film is strengthened by haking, and then the exposed portion is etched using an etching device. A schematic diagram of the etching apparatus is shown in FIG. This etching device 1 includes a conveyor 3 that conveys a metal material 2 and a plurality of injectors 4 that spray etching liquid onto the metal material 2 from both upper and lower directions.
As shown in an enlarged cross-sectional view of FIG. 2, the etching liquid is sprayed onto the metal material 2 by swinging from side to side.

[Problem to be solved by the invention]

As ICs become more highly integrated and multi-functional, the number of pins on lead frames increases, but chip size and package size are limited to a certain extent, so lead pinching at the tip of the lead on the island side increases. As the lead width becomes narrower, the lead width and the lead spacing also become smaller, and as shown in the enlarged cross section of FIG. 3, it has become important to ensure the flat lead width 5 and the lead spacing 6 necessary for IC assembly. This is because if the flat width of the leads is too small, wire bonding will not be possible, and if the lead spacing is too small, the leads may come into contact with adjacent leads.

When normal etching is performed, as shown in FIG. 4, an undercut 8 is created which is etched to the inside of the resist film 7, and the central part 9 of the metal material in the thickness direction is etched from the surface part 10 of the material. side etching 11 occurs with a delay. If the amount of etching becomes large, the undercut 8 becomes too large as shown in FIG. 5, and the flat width 5 of the lead becomes narrow, and if the amount of etching becomes small, the side etch 11 becomes too large as shown in FIG. 6.

Fig. 7 shows an example of a quad-type lead frame with the island periphery enlarged. When etching is performed using the conventional method, the amount of etching at the tips of the inner leads A and A' in Fig. B in the direction perpendicular to the direction (arrow),
Different from B'. That is, a phenomenon occurs in which etching progresses slowly in the perpendicular directions B and B', while etching progresses quickly in the transport directions A and A', making it difficult to control the amount of etching.

The narrower the lead pitch, the more uniform the etching amount within the metal sheet must be, but with conventional methods, the non-uniformity actually increases.

The present invention has been made in view of the above circumstances, and an object of the present invention is to ultimately equalize the amount of etching within a metal material sheet in manufacturing a lead frame with a narrow lead pitch by etching.

[Means to solve the problem]

In order to achieve the above object, the method of the present invention changes the orientation of the metal material by 90 degrees when the etching has progressed substantially halfway.
The feature is that the remaining etching is done after changing the pattern. In the present invention, for example, as shown in FIG. 8, a space 13 is provided between two etching chambers 12a and 12b so that the metal material 2 can be taken out when about half of the etching has been completed. This can be carried out by rotating the chamber 90° from state 2a to state 2b and sending it to the next chamber. The etching time at this time may be adjusted by adjusting the conveyor speed of the etching device. Etching time varies depending on the condition of the etching solution, the type of metal material, the pattern to be formed, etc., but after actually etching the finished product, measure the lead flat width, lead spacing, and each dimension to determine the required lead size. An appropriate etching time may be determined to satisfy flat width, spacing, and dimensional tolerances.

Alternatively, it is also possible to use a conventional etching device as is. For example, assuming an appropriate etching time for the metal material to be etched, determine the conveyance speed of the metal material in the etching device so that the metal material is etched for half of that time, and then etching the metal material through the etching device by about half the time. After etching, the orientation of the metal material is rotated by 90 degrees, and the conveyance speed is adjusted so that the metal material is etched for an appropriate time to satisfy the dimensions of the shape to be obtained by passing it through the same etching device again, and the rest is etched. be.

[Effect]

The reason why the method of the present invention ultimately makes the amount of etching uniform in each part of the lead frame piece is as follows. That is, since the etching liquid injector 4 is oscillating as shown in FIG. 2, the etching liquid is swept over the metal material in a direction perpendicular to the conveyance direction, leading to the leads A and A' in FIG. In this case, since the direction of the lead is perpendicular to the direction in which the etching liquid is swept away, the etching liquid easily hits the side surface of the lead, making it easier to etch the side surface of the lead. Etching 2 in the lead of
It is difficult to be etched because it runs parallel to the flow of the night. Therefore, if the direction of the metal material 2 is changed by 90'' during etching, the final etching of each part of the metal material will be uniform, and the width lead spacing of each lead in the lead frame can be made equal.

〔Example〕

A 42A11oy material with a plate thickness of 0.15 fins was coated with photoresist FPER manufactured by Fuji Yakuhin Co., Ltd., and dried. A 100-bin lead frame pattern with a lead pitch of Q and 3 mm was applied to both the front and back sides of the film using an ultra-high pressure mercury lamp light source. The film was exposed to light and baked, developed with trichlorethylene, and then baked. This metal material was transported through an etching apparatus having an oscillating injector as shown in FIG. 2 that injects ferric chloride solution from both the upper and lower surfaces, and was etched for 10 minutes.

Next, the orientation of the metal material was changed by 90 degrees and the metal material was again subjected to the above-mentioned etching apparatus, and etching was performed until the desired dimensions were obtained.

One piece was selected from each of the four sheets of three lead frames produced by this method, and the flat width of all the lead glue was measured for a total of four pieces, as shown in Table 1. The results were as shown in Table 1. I found out that it was.

〔Effect of the invention〕

According to the present invention, it has become possible to accurately manufacture a lead frame with a lead pitch of Q, 3 myr or less.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the etching device, Fig. 2 is an enlarged sectional view of the etching liquid injector, Figs. 8 is an enlarged view showing an example of a quad lead frame around an island, and FIG. 8 is a view showing an embodiment of the method of the present invention. ■... Etching device, 2... Metal material, 4... Etching liquid injector, 5... Lead flat width, 6... Lead spacing, 8... Undercut, 11... Side etching, 12...Etching chamber Figure 1

Claims (1)

[Claims] Apply photoresist to a sheet of metal material, expose it to light,
In a method of manufacturing a lead frame by developing a photoresist to leave a lead frame shape, and then spraying an etching solution onto the metal material while transporting the metal material to etch the exposed metal parts, etching is substantially When the metal material has progressed halfway, the direction of the metal material is changed to 90°.
A method for manufacturing a lead frame, characterized by etching the remaining parts.