JP2001024128A - Manufacture of lead frame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure flatness of a flexible board or a circuit board by locally heating the part of a metal frame applied with adhesive and bonding a flexible board to the metal frame thereby retarding thermal deformation of the metal frame and the flexible board. SOLUTION: Using a heat block 4 provided with a part 4A for locally heating a metal frame 1, a flexible board 2 comprising a polyimide insulating film formed with a plurality of circuit boards 2A is bonded to the metal frame 1 through thermoplastic or thermosetting adhesive 3. The heating part 4A is formed to have a level difference from the surface of the heat block 4 and heats the part of the metal frame 1 applied with adhesive 3 from the rear side over contact length and width smaller than those of the part applied with adhesive 3. According to the method, thermal deformation of the metal frame 1 and the flexible board 2 can be retarded while ensuring flatness of the flexible board 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, and more particularly to a lead for manufacturing a lead frame in which a flexible substrate having a wiring pattern formed on an insulating film such as polyimide is adhered and fixed to a metal frame such as a copper alloy. The present invention relates to a frame manufacturing method.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for miniaturized and highly integrated semiconductor devices. In order to utilize existing equipment and reduce waste of materials, a metal frame and wiring on an insulating film such as polyimide are used. A lead frame in which a flexible substrate on which a pattern is formed is combined has been proposed.

A flexible board is a circuit board formed by applying a photo application and an etching process to a conductive layer such as a copper foil provided on an insulating film to form a wiring pattern.
(Ball Grid Arrey) etc. In a semiconductor device manufacturing process, a semiconductor device is formed by mounting a semiconductor element on a circuit board and then resin-sealing with a mold resin, and separating the semiconductor device from a metal frame in a later process. Commercialize.

As a method of fixing a flexible substrate to a metal frame, bonding using an adhesive is performed. First, a rectangular opening is formed in a metal frame, and an adhesive is applied to the periphery of the opening. Next, the flexible substrate is punched out with a press die so as to have a size larger than the opening of the metal frame by the amount of the attachment, and is positioned on the metal frame. Then, the metal frame and the flexible substrate are thermocompression-bonded by using a bonding die such as a heat block heated to a predetermined temperature. As a result, the adhesive is melted, and the flexible substrate is bonded to the metal frame.

The lead frame formed in this manner can be used in an existing semiconductor manufacturing apparatus for manufacturing a QFP (Quad Flat Package), and a CSP (Chip Scale Package) can be used while suppressing an increase in equipment cost. Can be manufactured. Further, since the required amount of the insulating film as the flexible substrate is bonded to the metal frame, the amount of the insulating film used can be reduced.

[0006]

However, according to the conventional lead frame manufacturing method, when a metal frame having a different coefficient of thermal expansion and a flexible substrate are thermocompression-bonded with a heat block, the thermally expanded metal frame and the flexible substrate contract. Since there is a difference in the amount of expansion and contraction when the flexible substrate is deformed, the flexible substrate is deformed such as warping or bending, and the flatness of the circuit board is reduced. There is a problem that it becomes possible. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for manufacturing a lead frame capable of suppressing thermal deformation of a metal frame and a flexible substrate and securing flatness of a flexible substrate or a circuit substrate.

[0007]

According to the present invention, there is provided a lead frame for bonding a flexible substrate having a wiring pattern formed on an insulating tape to a metal frame with a thermoplastic or thermosetting adhesive. In the manufacturing method, there is provided a lead frame manufacturing method for locally heating an application portion of the adhesive applied to the metal frame and bonding the flexible substrate to the metal frame.

According to the above-described lead frame manufacturing method, by locally heating the adhesive applied portion,
The difference in the amount of expansion and contraction during thermocompression bonding between the metal frame and the flexible substrate is reduced.

[0009]

FIG. 1 shows a method for manufacturing a lead frame according to an embodiment of the present invention.
(B) is a cross section along the line bb in (a). An apparatus for implementing this lead frame manufacturing method has a heat block 4 provided with a heating unit 4A for locally heating the metal frame 1, and is made of an insulating film such as polyimide on which a plurality of circuit boards 2A are formed. The flexible substrate 2 is bonded to the metal frame 1 with a thermoplastic or thermosetting adhesive 3. The heating section 4A is formed to have a step with the surface 4B of the heat block 4, and the metal frame 1
Is formed so as to heat the back surface of the application part of the adhesive 3 with a contact length and a contact width smaller than the application part of the adhesive 3 applied to the adhesive. In the present embodiment, the height h of the heating unit 4A is 1.5 mm. The height h only needs to have a height at which the metal frame 1 can be partially heated.
Preferably, it is provided in the range of 0.2 mm to 5.0 mm.

FIGS. 2A to 2D show steps of manufacturing a lead frame by the above-described lead frame manufacturing method. FIG. 2A shows a step of forming the metal frame 1.
Etching is performed on a copper alloy having a length of 160 mm, a width of 40 mm, and a thickness of 200 μm to form four 30 mm × 30 mm square openings 1 </ b> A. In addition, a plurality of guide holes 1B are formed on two sides (both sides) in the width direction of the opening 1A for positioning during lead frame conveyance.

FIG. 2B shows a step of applying an adhesive to the metal frame 1, wherein the opening 1 formed in the metal frame 1 is formed.
The adhesive 3 is applied by a machine-controlled dispenser in a straight line along two sides in the frame width direction of the periphery of A.

FIG. 2C shows a process of attaching a film to the metal frame 1. The flexible substrate 2 punched into a size of 30 mm × 34 mm is positioned in the opening 1 A of the metal frame 1 and adhered by the adhesive 3. Fix it. Specifically, the flexible substrate 2 is arranged on the metal frame 1 to which the adhesive 3 has been applied, and the heating section 4A of the heat block 4 is brought into contact with the back surface of the application section of the adhesive 3. At this time,
It is preferable that the flexible substrate 2 be pressed from above to make close contact with the heating section 4A of the heat block 4. Heating unit 4
A heats the application part of the adhesive 3 so that the adhesive 3
Is melted, and the film 2 is bonded to the metal frame 1.

FIG. 2D shows the back surface of the metal frame 1 to which the flexible substrate 2 shown in FIG.
A is provided with four circuit boards 2A on which a predetermined wiring pattern is formed and a mold line 2B as a reference line. A semiconductor device is manufactured by applying a resist resin to this circuit board 2A, mounting a semiconductor element, connecting an electrode pad of the semiconductor element to a bonding pad of the circuit board 2A, and performing resin molding. Commercialize.

According to the above-described lead frame manufacturing apparatus, the heat block 4 having the heating section 4 locally heats the metal frame 1 and does not heat the portions other than the adhesive application section, so that the adhesive 3 In this case, the heat of the heat block 4 can be efficiently transmitted and quickly melted, and the time required for bonding the flexible substrate 2 can be shortened by improving the heat conductivity. In addition, since the heat block 4 does not come into contact with the portion where the adhesive 3 is not applied, thermal deformation of the metal frame 1 is prevented, and as a result,
The flatness can be improved without warping or bending of the flexible substrate 2.

In the above embodiment, the metal frame 1
Although the adhesive 3 is applied to two sides in the frame width direction of the periphery of the opening 1A formed in the above, the adhesive 3 may be applied to three or four sides. Although the thermosetting adhesive 3 is applied to the metal frame 1, the adhesive 3 may be applied to the flexible substrate 2.

The lead frame manufactured according to the above-described embodiment is, for example, an FBGA (Fine Pitch Ball).
Grid Arrey), CSP, DRAM (Dinamic Random Ac)
cessMemory), SRAM (Static Random Access Memory)
For semiconductor devices such as memories, CPUs, and MPUs.

[0017]

As described above, according to the lead frame manufacturing method of the present invention, since the application portion of the adhesive applied to the metal frame is locally heated to adhere the flexible substrate, the metal frame and the Thermal deformation of the flexible substrate can be suppressed, and flatness of the flexible substrate can be ensured.

[Brief description of the drawings]

FIG. 1A is a perspective view of a heat block of an apparatus for performing a lead frame manufacturing method according to an embodiment of the present invention. FIG. 1B is a view of the heat block taken along line bb in FIG. Sectional view

FIGS. 2A to 2D are explanatory views showing a lead frame manufacturing process based on the lead frame manufacturing method of the present invention.

[Explanation of symbols]

 1, metal frame 1A, opening 1B, guide hole 2, flexible board 2A, circuit board 2B, mold line 3, adhesive 4, heat block 4A, heating section 4B,

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hironori Shimazaki 3550 Kida Yomachi, Tsuchiura-shi, Ibaraki Hitachi Cable, Ltd. System Materials Research Laboratory F-term (reference) 5F067 AA11 CC01 CC08 DA00 DA05 DA16

Claims (4)

[Claims] 1. A lead frame manufacturing method for bonding a flexible substrate having a wiring pattern formed on an insulating tape to a metal frame with a thermoplastic or thermosetting adhesive, wherein the application of the adhesive applied to the metal frame is performed. A method of locally heating a portion to adhere the flexible substrate to the metal frame. 2. The lead frame manufacturing method according to claim 1, wherein the local heating locally heats a back surface of a portion where the adhesive applied to the metal frame is applied. 3. The method for manufacturing a lead frame according to claim 1, wherein said local heating is performed by bringing a protrusion formed on a heat block and having a height of at least 0.2 mm or more into contact with said back surface. 4. The local heating is performed by bringing a protrusion formed on a heat block into contact with the back surface with a contact length and a contact width smaller than those of the adhesive applied portion.
13. The lead frame manufacturing method according to any one of the preceding claims.