JPH04144263A - Lead frame and manufacture thereof - Google Patents

Abstract

PURPOSE:To inhibit a solder from flowing out to the outside of terminal parts and to make possible a mounting of a multipin to a semiconductor integrated circuit by a method wherein groove parts are respectively formed in outer leads before the outer leads come into contact to the terminal parts on a printed circuit board and solder parts are respectively formed in the groove parts. CONSTITUTION:At the time of manufacture of a lead frame, groove parts 10 are respectively formed in the surfaces, which come into contact to terminal parts 6 on a printed circuit board 5, of outer leads 2 and a soldering paste is ready-buried in the groove parts 10. Whereupon, the outflow of a solder 1 at the time of heating is suppressed on the peripheries of the groove parts 10 and the outflow to the outside of the terminal parts 6 stops causing. Moreover, as the area, which comes into contact to the lead frame, of the solder is increased by the amount of the groove parts 10, the bonding strength of the solder becomes high. In the manufacture of such a lead frame, it is possible to use a method, wherein desired patterns are respectively made of a photoresist 8 on both surfaces of a metal plate 7 and an etching is performed from both surfaces with an etching liquid, and the manufacture has only to be designed so as to provide opening parts 9 in the photoresist in parts, which correspond to the groove parts 10, of the surface of the plate 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lead frame for mounting a semiconductor integrated circuit, and particularly to a structure and manufacturing method of a lead frame with a large number of bins.

[Prior Art] A conventional lead frame is manufactured by pressing a metal plate 7 made of an iron-based alloy such as 42 alloy (N i 42% by weight, Fe balance) or a copper-based alloy such as phosphor bronze. , by press working with a mold having a desired pattern, or by etching, that is, by coating the photoresist 8 on the metal plate 7, exposing and developing using a mask having a desired pattern, After patterning the photoresist film 8, it was manufactured by etching it with an etching solution such as ferric chloride solution.

[Problem to be solved by the invention]

2. Description of the Related Art In the field of semiconductor integrated circuits, especially semiconductor integrated circuits having multiple functions such as semiconductor integrated circuits for specific applications, the number of terminals tends to increase. On the other hand, semiconductor integrated circuit chips are desired to be highly integrated and are subject to size constraints. For this reason, the pitch of the terminals has to be narrowed.

As described above, as the number of terminals of semiconductor integrated circuits and the pitch between the terminals become narrower, there is a corresponding demand for a lead frame with a larger number of bins and a narrower pitch between the inner lead part 3 and the outer lead part 2. is increasing.

On the other hand, when mounting a semiconductor integrated circuit using a multi-pin lead frame, a so-called surface mounting method is generally used, in which the terminals 6 are soldered onto the surface of the terminals 6 provided on the printed circuit board 5. The method used for soldering is to apply solder paste and melt it by heating. However, as the pitch of the outer leads 2 becomes narrower, the pitch of the corresponding terminals 6 on the printed circuit board 5 also becomes narrower, resulting in the problem that short circuits due to solder flowing out of the terminals during heating and melting cannot be avoided. is born.

[Means to solve the problem]

In order to solve the above problems, in the present invention, a groove 10 is formed in advance on the surface of the outer lead 2 that contacts the terminal portion 6 on the printed circuit board 5, and a solder part is formed in the groove 10. .

[Detailed Description of the Invention] In order to solder the resin-sealed semiconductor integrated circuit onto the printed circuit board 5, solder paste is applied on the terminals 6 on the printed circuit board 5 in advance, and solder paste is applied to the outer surface of the lead frame. The joint portion of lead 2 is heated and joined.

As the pitch of the outer leads 2 becomes narrower, it becomes necessary to correspondingly narrow the pitch of the terminal portions 6 on the printed circuit board 5. Therefore, during heating and melting, the solder that flows out comes into contact with the solder on the adjacent terminal 6, causing the above-mentioned problem of causing a short circuit.

In order to solve this problem, when manufacturing the lead frame, the printed circuit board 5 of the outer lead 2 is
By forming a groove 10 on the surface in contact with the upper terminal 6 and filling the groove 10 with solder paste, the solder flowing out during heating is suppressed around the groove 10 and does not flow outside the terminal 6. It disappears. Furthermore, since the contact area between the solder and the lead frame is increased by the groove 6, the adhesive strength is increased.

A method for manufacturing such a lead frame is to use an etching method to manufacture a normal lead frame. In other words, a desired pattern is formed on both sides of a metal plate 7 using photoresist 8, and corrosion is removed from both sides using an etching solution. It is possible to use the method of manufacturing the groove part 10 as it is.
It is only necessary to design the photoresist so that the opening 9 is provided in a portion corresponding to . After forming the pattern of photoresist 111B, if etching is applied from both sides,
Since only one side of the groove portion 10 is corroded, a groove having a depth equivalent to half the thickness of the metal plate 7 is formed. The shape of the opening of the groove 10 is not specified, and the design should be such that the solder does not leak out later and a suitable adhesive strength is obtained.The method of filling the formed groove 10 with solder is also specified. However, the printing method is simpler.

〔Example〕

42 alloy (42% by weight Ni, remaining Fe) was used as the metal plate, and a negative photoresist PMER (trade name) manufactured by Tokyo Ohka Kogyo ■ was dip coated on both sides (see Fig. 4(a)), as desired. Exposure using a mask with a pattern of
Development was performed and the photoresist film was patterned (
(See Figure 4(b)).

At this time, the mask pattern is designed in advance so that the photoresist in the portions that should become the grooves is removed.

Thereafter, etching was performed from both sides using a ferric chloride solution to form a lead frame (see FIG. 4(c)).

At this time, a groove with a depth equivalent to half the thickness of the metal plate was formed.

After peeling off the photoresist, a solder portion was formed by printing a solder paste, and the intended lead frame was manufactured (see FIG. 4(d)).

〔Effect of the invention〕

When a semiconductor integrated circuit using the lead frame according to the present invention is mounted on a printed wiring board, solder is prevented from flowing out of the terminal portion, making it possible to mount a multi-pin semiconductor integrated circuit. Further, this lead frame can be manufactured using a normal etching method, and the solder layer can also be formed by a printing method, so it has the advantage that it can be manufactured by a simple method.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment of the lead frame of the present invention. Fig. 2 shows a state in which the chip of a semiconductor integrated circuit is sealed with resin using the adhesive 7 frame of the present invention, and the tip of the outer lead is formed by bending so that it can be mounted on a printed circuit board. It is a schematic explanatory diagram. Third
The figure is an explanatory cross-sectional view showing a state in which the semiconductor integrated circuit element using the lead frame of the present invention is soldered onto the printed circuit board. It is a cross-sectional explanatory diagram showing the state,
FIG. 3(b) is an explanatory cross-sectional view showing a state in which a semiconductor integrated circuit element using a lead frame manufactured by a conventional method is soldered onto a printed circuit board. Figure 4(a)-(
d) is a cross-sectional explanatory view showing an example of the lead frame manufacturing method of the present invention in the order of steps; 1...Solder part 3...Inner lead 5...Printed circuit board 7...Metal plate 9...Front 10 corresponding to the groove part...Groove part 2...Outer lead 4...Sealing Stopper resin 6...Terminal part 8...Opening part of photoresist resist

Claims (1)

[Claims] (1) A groove portion 10 is formed in a portion of the outer lead 2 corresponding to the terminal portion 6 on the printed circuit board, and the groove portion 10
A lead frame characterized by being provided with a solder portion 1. (2) When manufacturing a lead frame by forming a desired pattern on both sides of the metal plate 7 with photoresist 8 and etching it, it is recommended to form the groove part 10 by etching one side of the metal plate and then form the solder part 1 in the groove part 10. A method for manufacturing a lead frame according to claim (1).