JP3358313B2 - Lead frame manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame manufacturing method, and more particularly, to a lead frame having a thin multi-pin lead frame having an insulating resin dam bar on at least one of an inner lead and an outer lead. It relates to a manufacturing method.

[0002]

2. Description of the Related Art An example of a lead frame manufacturing process will be briefly described. First, the surface of the metal plate serving as a lead frame is degreased and leveled. Then, on both sides of the metal plate,
For example, a water-soluble negative photosensitive resin composed of polyvinyl alcohol and ammonium bichromate is applied.
Then, using two masks each having a light transmitting portion for a portion to be a pattern of the lead frame and a light shielding portion other than the pattern portion of the lead frame, applying one mask to one surface of the metal plate and applying the other mask to the other surface of the metal plate Then, another mask is applied to the position opposite to the above, and ultraviolet light is exposed from both sides, and photo-curing of the photosensitive resin in a portion to be a pattern of the lead frame is performed.

Next, by performing development, the photosensitive resin in the uncured portion, that is, the photosensitive resin other than the portion that becomes the pattern of the lead frame is removed. Next, the etching of the metal plate is performed from both sides using an etchant, and the metal plate other than the portion to be the pattern of the lead frame is removed by etching. Leave. Next, the photosensitive resin is stripped. Subsequently, the tip of the inner lead is partially precious metal-plated by a known method, for example, by spraying a plating solution, and the metal plate is punched into a required shape to obtain a lead frame.

Next, in a lead frame for a semiconductor IC, an IC chip is mounted on the lead frame, and the IC chip is mounted on the lead frame.
After wire bonding the chip and the lead frame, molding with an insulating resin is performed. Therefore, in order to prevent the insulating resin from flowing out from the gap between the outer leads when the resin is molded into the lead frame, FIG.
As shown in (1), a bank (hereinafter, referred to as a dam bar) is added to the lead frame so as to cross the outer lead 3. Next, the dam bar 1 in FIG. 3 connects the outer leads 3 and if used as it is, the outer leads 3 have the same potential and short-circuit. Therefore, after the insulating resin is molded, the dam bar 1 is formed by a punching die or the like. It has been cut and removed.

However, in recent years, lead frames have a tendency to be thinner and have more pins. For example, in a lead frame called a layer for a ceramic package, the package size is large, the number of pins is increased from 200 pins to 300 pins or more, and the plate thickness is 10
It is very thin, from 0 μm to 150 μm. For this reason, the pitch between the outer leads has become narrower, and it has become very difficult to cut and remove the dam bar using a punching die.

[0006] As described above, the partial noble metal plating treatment to be applied to the tip of the inner lead is usually performed by spraying a noble metal plating solution to the tip of the inner lead. Therefore, at the time of precious metal plating, a masking jig is brought into close contact with the surface of the lead frame on which precious metal plating is to be performed, and then plating is performed by spraying a precious metal plating solution onto the tip of the inner lead.

However, in this case, the use of a masking jig prevents the formation of a plating film on an unnecessary portion of the upper surface of the lead frame, but the noble metal plating solution leaks to the side surfaces of the inner leads, and the plating solution flows around the side surfaces. It was difficult to prevent the formation of unnecessary plating films on the side surfaces of the inner leads.

[0008] Therefore, unnecessary plating solution leaks excessively to the side surfaces of the inner leads. For example, when an unnecessary side plating film is formed near the outer leads, the resin and the resin may be removed when molding the insulating resin. Poor adhesion of the lead frame occurs, and as a result, a problem may occur in the durability of the IC package.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing a lead frame in which a dam bar is formed of an insulating resin in a multi-pin lead frame having a small thickness. An object of the present invention is to obtain a lead frame that does not have a lead frame.

[0010]

That is, the present invention provides a method for manufacturing a lead frame having a dam bar made of an insulating resin on at least one of an outer lead and an inner lead. In addition, a lead frame without a dam bar is inserted into a concave portion having a concave portion in the shape of a lead frame without a dam bar, and an insulating resin is filled by squeegeeing the concave portion having a shape corresponding to the dam bar, thereby filling light or ultraviolet light. It is an object of the present invention to solve the above-mentioned problem by providing a method for manufacturing a lead frame, which comprises curing a resin filled by the method.

[0011]

According to the present invention, by attaching a dam bar using an insulating resin to the outer lead of a lead frame, it is no longer necessary to cut and remove a metal dam bar using a mold or the like, which has been performed with a metal dam bar. . Next, when a connecting portion using an insulating resin is attached to the inner lead (hereinafter referred to as a dam bar for inner lead for convenience),
During precious metal plating, the sprayed precious metal plating solution can be prevented from leaking to the side surfaces of the inner leads. In addition, since the tip of the inner lead, which has become ultra-fine due to the increase in the number of pins, is fixed with resin, it is possible to suppress the variation of the inner lead during the manufacturing process, Deformation defects of the lead can be prevented.

Further, in the present invention, when filling the concave portion with the insulating resin, the excess resin applied to the lead portion can be scraped by stroking with a squeegee.
Therefore, the insulating resin does not adhere to and remain in an extra portion on the lead frame, and a plating defect and a bonding defect due to the extra resin adhesion can be prevented.

Further, in the present invention, if a light or ultraviolet curable resin is used as the insulating resin for forming the dam bar, the resin filled in the concave portion can be cured in a short time by irradiating the resin with light or ultraviolet light.

[0014]

An embodiment of the present invention will be described with reference to the drawings. In FIG. 1 described below, only a part of the inner lead and the outer lead of the lead frame is omitted for the purpose of describing the embodiment of the present invention.

First, as shown in FIG. 1A, a lead frame 10 for molding is prepared. In the lead frame 10 for molding, a dam bar 1 for preventing resin outflow at the time of resin molding is provided in the outer lead 3 portion, and the outer lead 3 is connected by the dam bar 1. Also,
When the plating solution is sprayed on the noble metal plating area 5 of the inner lead 4 part, the dam bar 2 for the inner lead is moved to the noble metal plating area 5 of the inner lead 4 part in order to prevent the plating solution from leaking to the side surface of the inner lead 4. Provided at the boundary, and inner dam 4 with inner dam 4
Connected comrades.

Next, the above-mentioned lead frame for molding 1
1 is buried in, for example, a silicone resin or the like, as shown in FIG. 1B, and then, the lead frame 10 for molding is removed from the silicone resin. As a result, the female mold 6 is obtained as a concave mold in which the mold of the molding lead frame 10 remains as a concave.

Next, the lead frame 8, which has neither the dam bar 1 nor the inner lead dam bar 2 but has the same shape as the above-mentioned molding lead frame 10 except for the above, is finally obtained as a product. Into the female mold 6. In this state, in the female die 6, the dam bar 1 and the inner lead dam bar 2 are left as concave portions.

Next, as shown in FIG. 1 (c), while the lead frame 8 is being fitted into the female mold 6, the dam bar 1 on the female mold and the concave portion corresponding to the inner lead dam bar 2 are, for example, UV-curable. Epoxy resin, etc.
Light or ultraviolet curable resin 7 having an insulating property is filled.

Next, as shown in FIG.
And by squeezing the lead frame 8 with a squeegee 9 to densely fill the concave portion with the resin 7,
Excess resin on the lead frame 8 is scraped off.

Next, the resin 7 filled in the concave portion is cured by irradiating light or ultraviolet light. Next, by taking out the lead frame 8 with the resin 7 from the female mold 6, a lead frame with a dam bar 1 made of insulating resin and a dam bar 2 for inner leads shown in FIG. 2 is obtained. Next, a manufacturing process such as precious metal plating and resin molding is performed on the lead frame by a known method to obtain an IC package.

In the above embodiment, after the concave portion is filled with the resin 7, excess resin is scraped off with the squeegee 9. Both steps, that is, scraping of a suitable resin, may be performed simultaneously. Further, in the above embodiment, both the dam bar 1 and the inner lead dam bar 2 are formed on the lead frame 8, but either one of them may be formed if necessary.

[0022]

According to the present invention, by attaching a dam bar using an insulating resin to the outer lead of the lead frame, the metal dam bar can be cut and removed using a punching die or the like, which has been performed with a metal dam bar. This eliminates the necessity of performing such a process, so that it is possible to prevent defective deformation of the extra-fine outer lead caused by cutting and removing the dam bar using a conventional die for punching, and to improve production efficiency. Next, when a dam bar for inner leads using insulating resin is attached to the inner leads, the noble metal plating solution sprayed during noble metal plating can be prevented from leaking to the side of the inner leads, and the durability of the IC package due to resin molding failure Can be prevented from decreasing. In addition, since the tip of the inner lead, which has become ultra-fine due to the increase in the number of pins, is fixed with resin, it is possible to suppress variations in the inner lead during the manufacturing process, and due to external pressure vibration during manufacturing and the inner roller caused by entanglement of the transport roller. Deformation defects of the lead can be prevented.

In the present invention, when filling the concave portion with the insulating resin, the excess resin is scraped by stroking with a squeegee. Therefore, the insulating resin does not adhere to and remain in an extra portion on the lead frame, and a plating defect and a bonding defect due to the extra resin adhesion can be prevented.

Furthermore, in the present invention, if a light or ultraviolet curable resin is used as the insulating resin forming the dam bar, the curing of the resin filled in the concave portion can be performed in a short time by irradiating light or ultraviolet light. It can be said that the present invention is practically excellent in manufacturing a multi-pin lead frame.

[0025]

[Brief description of the drawings]

FIGS. 1A to 1D are perspective explanatory views showing an embodiment of a method of manufacturing a lead frame provided with an insulating resin dam bar according to the present invention in the order of steps.

FIG. 2 is a plan view showing one embodiment of a lead frame provided with an insulating resin dam bar of the present invention.

FIG. 3 is a plan view showing an example of a conventional lead frame provided with a dam bar.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dam bar 2 Dam bar for inner lead 3 Outer lead 4 Inner lead 5 Plating area 6 Female type 7 Insulating resin 8 Lead frame 9 Squeegee 10 Lead frame for molding

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Claims (3)

(57) [Claims] 1. A method for manufacturing a lead frame having a dam bar made of an insulating resin on at least one of an outer lead and an inner lead, wherein the recess has a shape corresponding to the dam bar, and has a recess having no dam bar. A lead frame without a dam bar is inserted into a concave portion having a shape, and a concave portion having a shape corresponding to the dam bar is filled with an insulating resin and cured. 2. The method according to claim 1, wherein the insulating resin is a light or ultraviolet curable resin. 3. The method for manufacturing a lead frame according to claim 1, wherein the insulating resin is applied to the concave portion having a shape corresponding to the dam bar, and then the concave portion is filled with the squeegee.