JPH07211835A - Manufacture of lead frame - Google Patents

Abstract

PURPOSE:To prevent inner lead distortion due to tie bar cut of an inner lead, and facilitate the bonding position alignment of an inner lead frame and an outer lead frame, when pitch is narrowed, the number of pins is increased, and thickness is reduced, in a bonded lead frame wherein the inner lead and the outer lead are formed by different systems and bonded together. CONSTITUTION:When an inner lead frame 1 is formed by additive plating, an inner lead tie bar 4 is set on the outside of the bonding part to an outer lead frame 2, and an inner lead 3 is fixed with a polyimide tape 8. Then an inner lead tie bar cut part is cut, and the inner lead frame 1 is bonded to the outer lead frame 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a lead frame of a semiconductor package which can realize a narrow pitch and a large number of pins and high reliability.

[0002]

2. Description of the Related Art In order to meet the demands of electronic devices for downsizing, weight saving, speeding up, and functioning of semiconductor packages, new forms are being developed one after another and the types of semiconductor packages are increasing. Further, as logic semiconductors such as CPUs and ASICs have more advanced functions, more input / output pins are required, which inevitably requires a narrower lead pitch. The limit of increasing the number of pins in the lead frame package is limited by the processing limit of the lead frame.

Conventionally, the lead frame is mechanically punched from one side with a metal plate such as copper or 42 alloy and the etching frame is formed with a pattern punched hole from both sides by a chemical etching method according to its manufacturing method. The islands for mounting the semiconductor elements, the inner leads for connecting the semiconductor elements with the bonding wires, and the outer leads for mounting on the wiring board are collectively manufactured. FIG. 8A is a sectional view of the lead of the conventional stamping frame, and FIG. 8B is a sectional view of the lead of the same etching frame. The stamping frame has a sufficient lead width for wire bonding and is cheaper in mass production than the etching frame. On the other hand, if there is a possibility that the shape of the etching frame will be changed by trial manufacture and evaluation, the frame shape can be changed relatively easily by changing the mask and the delivery time can be shortened. Therefore, the cost can be reduced. Also,
The etching frame is superior to the stamping frame in terms of microfabrication of the multi-pin frame, and currently, with a plate thickness of 0.15 mm, it is possible to manufacture about 350 pins against about 200 pins for a press frame.

Although the above-mentioned manufacturing method is mainly used for the lead frame, there is another manufacturing method called an additive method for forming the lead frame by depositing and depositing a required metal on the frame pattern shape by plating.
FIG. 9 is a schematic view of a lead frame manufacturing process by a conventional etching method. First, a resist is applied to the front and back surfaces of the metal material. Next, after masking and printing exposure,
develop. Then, an unnecessary portion is removed by etching and the resist is peeled off to obtain a desired lead frame.

Further, FIG. 10 is a schematic view of a manufacturing process of a lead frame by a conventional additive method. First, a resist is applied to the upper surface of the substrate, masked, baked and exposed, and then developed to remove unnecessary portions of the resist. Next, after plating the substrate, the resist is peeled off, and then the frame is peeled off from the substrate to obtain a desired lead frame.

In the etching which is advantageous for the narrow pitch, there is a drawback that the wire bonding surface becomes narrow as can be seen from the sectional shape of FIG. 8. In contrast, in the additive method, the sectional shape of the lead depends on the resist and the inner lead frame is When manufacturing, there is an advantage that a more stable bonding area can be secured.

In recent years, along with the increase in the number of pins of the lead frame, it is desired to make the frame thinner in the manufacturing process of the frame, but it becomes difficult to secure the mechanical strength due to this, so that the inner lead frame becomes narrower in lead pitch. , Which has a relatively large lead pitch and requires sufficient lead rigidity for lead forming in the assembly, is manufactured by another method, and the two are joined by thermocompression bonding, etc. to achieve a narrower pitch. There are many lead frames.

A description will be given below of a bonded lead frame in which the inner lead frame is manufactured by the additive method and the outer lead frame is manufactured by another method such as stamping and etching.

FIGS. 11A, 11B, and 11C are schematic plan views of the manufacturing process of the conventional bonded lead frame.
(A), (b), (c) is a manufacturing process sectional schematic diagram of the conventional joining lead frame, and FIG. 13 is a partially expanded view of the conventional inner lead frame. The manufacturing process will be described below. First, the inner lead frame 1 and the outer lead frame 2 shown in FIGS. 11A and 12A are separately formed. The inner lead frame 1 is manufactured by the additive method. In the figure, 3 is an inner lead, which is connected by an inner lead tie bar 4,
The inner lead 3 is made of an insulating material such as polyimide tape 8.
Is fixed. 7 is an island. The outer lead frame 2 is manufactured by stamping or etching. Outer leads 5 are formed on the outer lead frame 2, and the outer leads 5 are connected by outer lead tie bars 6.

As shown in FIGS. 11 (b) and 12 (b), the inner lead frame 1 and the outer lead frame 2 are aligned, and the leads, which have been surface-treated by silver plating or the like, are joined by thermocompression bonding or the like. After that, the portion corresponding to the lead gap of the inner lead tie bar 4 of the inner lead frame 1 is cut (FIG. 11C, FIG.
2 (c)), the lead frame is completed. In FIG. 13, the hatched portion indicated by reference numeral 10 is an inner lead tie bar cut portion.

[0011]

However, in order to narrow the pitch of the inner leads 3 and increase the number of pins, it is necessary to make the plate thickness of the inner lead frame 1 thinner than before for the convenience of processing. If so, there is a problem in that the mechanical strength of the inner lead frame 1 decreases. Further, if the pitch is narrowed and the number of pins is increased, the lead gap of the inner lead tie bar 4 of the inner lead frame 1 is also reduced, which makes it difficult to align the punch edge of the die for cutting the inner lead tie bar cut portion 10. As a result, the shape of the inner lead 3 such as twist and warp is easily deformed by this cutting process,
Even in the step of joining with the outer lead frame 2, there is a problem that lead misalignment and chipping are likely to occur, and the manufacturing of the punch blade edge becomes difficult.

Therefore, the present invention solves the above-mentioned conventional problems and prevents the inner lead frame from being deformed due to the tie bar cut even if the inner lead has a narrow pitch, a large number of pins, and a thin shape. It is an object of the present invention to provide a method for manufacturing a lead frame, which enables easy alignment of the outer lead frame.

[0013]

To this end, according to the present invention, the inner lead tie bar is set outside the joint between the inner lead frame and the outer lead frame, and the inner lead is fixed with an insulating material such as a polyimide tape. , Cut the entire tie bar of the inner lead frame. Alternatively, remove the inner lead tie bar and perform additive plating with a pattern design in which each inner lead is independent, fix the inner leads and islands with an insulating material such as polyimide tape, and then peel from the substrate to remove the tie barless inner A lead frame is manufactured and joined to the outer lead frame.

[0014]

According to the present invention, the inner tie bar cut portion in the tie bar cutting step has a simple shape due to the above-described structure. In addition, the inner lead tie bar itself is eliminated and the inner lead tie bar cutting step is eliminated to prevent deformation of the inner lead having weak mechanical strength. As a result, lead displacement and chipping at the time of joining are eliminated, and a highly reliable, narrow-pitch lead frame is manufactured.

[0015]

Embodiments of the present invention will now be described with reference to the drawings. 1 (a), (b), (c), (d), (e)
Is a schematic sectional view of the manufacturing process of the bonded lead frame of the first embodiment of the present invention, FIGS. 2A, 2B and 2C are schematic plan views of the same manufacturing process, and FIG. 3 is the first embodiment of the present invention. 3 is a partially enlarged view of the inner lead frame of FIG. The same components as those in the conventional example are designated by the same reference numerals. In FIG. 1A, the inner lead frame 1 is formed on the substrate 11 by the additive method and is peeled off from the substrate 11 at the time of additive plating (FIG. 1B). In this case, the inner lead tie bar 4 is formed outside the joint between the inner lead frame 1 and the outer lead frame 2. Next, the inner lead 3 is fixed with an insulating material such as a polyimide tape 8 (see FIG. 1C and FIG.
(See (a)), and the entire inner lead tie bar 4 is cut (see FIGS. 1 (d) and 2 (b)). In FIG. 3, a hatched portion indicated by reference numeral 10 is an inner lead tie bar cut portion. 1D and 2C, the outer lead frame 2 is separately formed by another method such as stamping or etching. Further, the inner lead frame 1 and the outer lead frame 2 are subjected to a surface treatment such as silver plating in advance at a joint portion, and the both are aligned and joined by thermocompression bonding to obtain a normal lead frame shape (FIG. 1). (E) and FIG.
(See (d)).

Thus, according to the first embodiment of the present invention,
Inner lead frame 1 due to narrower pitch and more pins
If the inner lead tie bar 4 is set outside the joint between the inner lead frame 1 and the outer lead frame 2,
After being fixed with an insulating material such as a polyimide tape 8, the entire inner lead tie bar 4 of the inner lead frame 1 is cut and removed. Therefore, the shape of the inner lead tie bar cut portion 10 is simpler than that of the conventional case shown in FIG. The inner lead 3 having a low mechanical strength can be prevented from being deformed when the tie bar is cut. As a result, the alignment of the inner lead frame 1 and the outer lead frame 2 can be facilitated, the lead displacement and the dropout at the time of joining can be eliminated, and a highly reliable narrow pitch lead frame can be manufactured.

Next, a second embodiment of the present invention will be described. 4 (a), (b), (c), and (d) are schematic cross-sectional views of the lead frame manufacturing process of the second embodiment of the present invention, and FIG. 5 (a), (b), (c). FIG. 3 is a schematic plan view of the same manufacturing process. In FIG. 4A and FIG. 5A, the inner lead frame 1 is designed in a shape without the inner lead tie bar 4 and manufactured by an additive method. However, the substrate 11 at the time of the additive is subjected to a pretreatment by electrolysis to improve the adhesion with the inner lead frame 1 and prevent the inner lead 3 from being damaged due to the peeling of the plating before taping. Also, substrate 1
When the inner lead frame 1 is peeled from the inner lead frame 1, the through holes 9 are provided to prevent the entrapment of air when taping the inner lead 3 and the island 7 (see FIG. 5).
(A)) This is performed after connecting and fixing with a square-shaped polyimide tape 8 that does not cover the area for joining with the outer lead 5. The joint portion between the inner lead frame 1 and the outer lead frame 2 is subjected to surface treatment such as silver plating in advance, and the both are aligned and joined by thermocompression bonding to obtain a normal lead frame shape ( 4 (c) and (d) and FIGS. 5 (b) and (c)).

Thus, according to the second embodiment of the present invention,
Inner lead frame 1 due to narrower pitch and more pins
Even if the thickness becomes thin and the strength becomes insufficient, the inner lead tie bar 4 is eliminated to design the individual leads independently, and the inner leads 3 and the island 7 are formed on the polyimide tape 8 etc. before the peeling from the substrate 11 after plating. The inner lead frame 1 having no tie bar is manufactured by fixing the inner lead frame 1 by fixing with an insulating material, and the deformation of the inner lead 3 having weak mechanical strength can be prevented by eliminating the tie bar cutting step. As a result, the alignment of the inner lead frame 1 and the outer lead frame 2 can be facilitated, the lead displacement and the dropout at the time of joining can be eliminated, and a highly reliable narrow pitch lead frame can be manufactured.

Next, a third embodiment of the present invention will be described. 6 (a), (b), (c), and (d) are schematic cross-sectional views of the manufacturing process of the bonded lead frame of the third embodiment of the present invention, and FIGS. ) Is a schematic plan view of the same manufacturing process. In FIGS. 6A and 7A, the inner lead frame 1 is designed in a shape without the inner lead tie bar 4 and manufactured by an additive method. However,
A metal 12 different from additive plating is thinly plated on the entire substrate 11 (FIG. 6B), a pattern is formed thereon with a resist, and then additive plating is performed. In addition, the inner lead frame 1 from the substrate 11
The peeling is performed by peeling off the thin plated metal 12 after connecting and fixing the inner lead 3 with the square-shaped polyimide tape 8 that does not cover the area for joining the island 7 and the outer lead 5. The joint portion between the inner lead frame 1 and the outer lead frame 2 is subjected to surface treatment such as silver plating in advance, and the both are aligned and joined by thermocompression bonding to obtain a normal lead frame shape ( 6 (c) and (d) and FIGS. 7 (b) and (c)).

As described above, according to the third embodiment, even if the inner lead frame 1 becomes thin and its strength becomes insufficient due to the narrower pitch and more pins, the inner lead tie bar 4 is eliminated and the individual leads are made independent. Tie bar-less inner lead in the manufacturing process in which the inner lead 3 is fixed with an insulating material such as a polyimide tape 8 before performing the pattern designing after the additive plating and by peeling off the thin plated portion from the substrate 11. By manufacturing the frame 1 and deleting the tie bar cutting step, it is possible to suppress inner lead deformation of the inner lead 3 having weak mechanical strength during the tie bar cutting step.

[0021]

As described above, according to the present invention, the inner lead tie bar of the inner lead frame is joined to the inner lead frame and the outer lead frame even if the lead frame has a narrow pitch, a large number of pins, and a thin shape. Set it to the outside of the part and fix the inner leads with an insulating material such as polyimide tape, then cut the entire inner lead tie bar of the inner lead frame, or separate the individual leads as tie barless with the inner lead frame By designing the pattern and fixing the inner leads with an insulator such as polyimide tape after additive plating and before peeling from the substrate, the inner lead frame without tie bars is made by manufacturing the tie barless inner lead frame. Prevent the inner Which facilitates bonding positioning of the lead frame and the outer lead frame. Also, by performing a pretreatment by electrolysis on the substrate at the time of additive plating, the adhesion with the inner lead frame is increased,
Prevents lead loss due to plating peeling before taping. Also, by peeling a metal different from additive plating, which is thinly plated on the entire substrate, the inner lead frame can be easily peeled off, whereby a highly reliable narrow pitch lead frame can be obtained.

[Brief description of drawings]

1A is a schematic sectional view of a manufacturing process of a bonded lead frame of a first embodiment of the present invention, FIG. 1B is a schematic sectional view of a manufacturing process of a bonded lead frame of a first embodiment of the present invention, and FIG. Manufacturing process cross-sectional schematic view of the bonding lead frame of the first embodiment of the present invention (d) is a manufacturing process cross-sectional schematic view of the bonding lead frame of the first embodiment of the present invention (e) is the first embodiment of the present invention Manufacturing process cross-sectional schematic diagram of bonded lead frame

FIG. 2A is a schematic plan view of the manufacturing process of the bonded lead frame of the first embodiment of the present invention. FIG. 2B is a schematic plan view of the manufacturing process of the bonded lead frame of the first embodiment of the present invention. Manufacturing process plan schematic diagram of the bonding lead frame of the first embodiment of the present invention (d) is a manufacturing process plan schematic diagram of the bonding lead frame of the first embodiment of the present invention

FIG. 3 is a partially enlarged view of the inner lead frame of the first embodiment of the present invention.

4A is a schematic cross-sectional view of the manufacturing process of the bonded lead frame of the second embodiment of the present invention. FIG. 4B is a schematic cross-sectional view of the manufacturing process of the bonding lead frame of the second embodiment of the present invention. (D) manufacturing process cross-sectional schematic diagram of the bonding lead frame of the second embodiment of the present invention

FIG. 5A is a schematic plan view of a bonding lead frame of the second embodiment of the present invention, and FIG. 5B is a schematic plan view of a manufacturing process of the joint lead frame of the second embodiment of the present invention. Schematic plan view of the manufacturing process of the bonding lead frame of the second embodiment of the present invention

6A is a schematic cross-sectional view of the manufacturing process of the bonded lead frame of the third embodiment of the present invention, and FIG. 6B is a schematic cross-sectional view of the manufacturing process of the bonded lead frame of the third embodiment of the present invention. (D) manufacturing process cross-sectional schematic diagram of the bonding lead frame of the third embodiment of the present invention

FIG. 7A is a schematic plan view of the manufacturing process of the bonding lead frame of the third embodiment of the present invention, and FIG. 7B is a schematic plan view of the manufacturing process of the bonding lead frame of the third embodiment of the present invention. Schematic plan view of the manufacturing process of the bonding lead frame of the third embodiment of the present invention

8A is a sectional view of a lead of a conventional stamping frame, and FIG. 8B is a sectional view of a lead of a conventional etching frame.

9A is a schematic diagram of a lead frame manufacturing process by a conventional etching method, and FIG. 9B is a schematic diagram of a lead frame manufacturing process by a conventional etching method, and FIG. 9C is a lead frame manufacturing process by a conventional etching method. Schematic diagram (d) is a schematic diagram of the lead frame manufacturing process by the conventional etching method (e) is a schematic diagram of the lead frame manufacturing process by the conventional etching method (f) is a schematic diagram of the lead frame manufacturing process by the conventional etching method (G) Schematic drawing of lead frame manufacturing process by conventional etching method

10A is a schematic diagram of a lead frame manufacturing process by a conventional additive method, FIG. 10B is a schematic diagram of a lead frame manufacturing process by a conventional additive method, and FIG. 10C is a lead frame manufacturing process by a conventional additive method. Schematic diagram (d) is a schematic diagram of a lead frame manufacturing process by the conventional additive method. (E) is a schematic diagram of a lead frame manufacturing process by the conventional additive method. (F) is a schematic diagram of a lead frame manufacturing process by the conventional additive method. (G) is a schematic diagram of a lead frame manufacturing process by the conventional additive method. (H) is a schematic diagram of a lead frame manufacturing process by the conventional additive method.

11A is a schematic plan view of a manufacturing process of a conventional bonding lead frame, FIG. 11B is a schematic plan view of a manufacturing process of a conventional bonding lead frame, and FIG. 11C is a schematic plan view of a manufacturing process of a conventional bonding lead frame.

12A is a schematic sectional view of a manufacturing process of a conventional bonding lead frame, FIG. 12B is a schematic sectional view of a manufacturing process of a conventional bonding lead frame, and FIG. 12C is a schematic sectional view of a manufacturing process of a conventional bonding lead frame.

FIG. 13 is a partially enlarged view of a conventional inner lead frame.

[Explanation of symbols]

 1 Inner Lead Frame 2 Outer Lead Frame 3 Inner Lead 4 Inner Lead Tie Bar 5 Outer Lead 6 Outer Lead Tie Bar 7 Island 8 Polyimide Tape 9 Through Hole 10 Inner Lead Tie Bar Cut 11 Substrate 12 Metal

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[Procedure amendment]

[Submission date] June 29, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Figure 9

[Correction method] Change

[Correction content]

FIG. 9 is a schematic view of a lead frame manufacturing process by a conventional etching method.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 10

[Correction method] Change

[Correction content]

FIG. 10 is a schematic view of a manufacturing process of a lead frame by a conventional additive method.

Claims (6)

[Claims] 1. An inner lead frame having an inner lead is formed by additive plating, and an outer lead frame having an outer lead is formed by stamping or etching to bond the inner lead frame and the outer lead frame. A method of manufacturing a lead frame, wherein an inner lead tie bar connecting the inner leads is provided outside a joint between the inner lead frame and the outer lead frame, and the inner lead is fixed with an insulator such as a polyimide tape. After that, the inner lead tie bar is cut and removed, and the inner lead tie bar is joined to the outer lead. 2. The inner lead is tie barless,
Pretreatment by electrolysis on the substrate at the time of additive plating increases the adhesion with the inner lead frame, is fixed with an insulating material such as polyimide tape, then peeled from the substrate and joined to the outer lead. The method for manufacturing a lead frame according to claim 1. 3. The inner lead is tie barless,
A metal different from additive plating is thinly plated on the entire substrate, a resist is used to create a pattern, then additive plating is applied, and the product is fixed with an insulating material such as polyimide tape. The method for manufacturing a lead frame according to claim 1, wherein the lead frame and the lead frame are joined together. 4. The lead frame according to claim 1, wherein all of the inner leads and the island inside the joint portion are fixed by an insulating material such as a rectangular polyimide tape. Production method. 5. The method of manufacturing a lead frame according to claim 1, wherein the inner lead inside the joint portion is fixed with an insulator such as a polyimide tape having a corner cut out. 6. The method of manufacturing a lead frame according to claim 4, further comprising a polyimide tape or an island provided with a through hole for preventing air entrapment during taping of the polyimide tape.