JPH07202114A - Film adhering method for lead frame, and chip adhering method for lead frame - Google Patents

Abstract

PURPOSE:To eliminate the poor bonding caused by the burrs generated when a film is punched by improving the glueability of a film and to decrease warped lead frames after adhesion of film. CONSTITUTION:A binder-applied polyimide film 7, on which polyetheramide- imide is applied to both sides, is fed to the prescribed place on a punching mold. The film 7 is punched into the prescribed shape, and they are sucked by a collet 23. A film 8 is carried to a solvent vessel 25, and the bonding agent is swellingly dissolved by bringing the surface to be adhered into contact with the solvent 24. At this time, the burrs generated when punching are dissolved and removed. The film 8 is conveyed to the prescribed position on a lead frame 19, and it is pressed thereto. Then, the film is carried to a point between heat blocks 5, dried up at 100 deg.C or thereabout, and its adhesion is completed. As the film is dried up at the low temperature of 100 deg.C, the warpage, due to the diffusion in linear expansion coefficient when the film returns to the normal temperature, is not generated on the lead frame.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for attaching a film to a lead frame for attaching a film to a lead frame via an adhesive, and a method for attaching a chip to a lead frame for attaching a semiconductor chip to the lead frame.

[0002]

2. Description of the Related Art COL (Chip on) that enables high-density mounting
Lead) or LOC (Lead on Chip) structure package, pre-fabricated lead frame by attaching a film with adhesive to the lead frame, in which adhesive is applied to one or both sides of high heat resistant polyimide film in advance for chip mounting. Has been put to practical use.

As shown in FIG. 2 (A), the method of attaching the film to the lead frame is as follows. The lead frame 9 conveyed to a fixed position of the die 6 is provided with the heater block 5 preheated to a predetermined temperature on the lower surface of the lead frame. Then, the adhesive-attached film 7 is punched out by the punch 1 and the die 2. Then, as shown in FIG. 2B, the film 8 punched through the lead frame 9 is pressed against the heater block 5 immediately below the die 2, and the film 8 is thermocompression bonded to the lead frame 9. In the figure, 3 is a stripper, 4 is a suction port for sucking the film 7 on the punch 1, 10 is a pilot hole, 11 is a pilot pin, 12 is a guide rail, 17
Is a guide post.

By the way, the initial shape of the film 7 attached to the lead frame is a simple rectangular shape for connecting the leads 9a according to the pattern of the lead frame 9 as shown in FIG. 3 (A). What was presented was the mainstream.

However, if the polyimide film has such a simple rectangular shape, the polyimide film has a high hygroscopic property, so that it is necessary to minimize the use area, but the polyimide film is also attached to an unnecessary portion between the leads 9a. Has a large area. Further, when the film area is large, the film 7 between the leads 9a is bent 13 due to the pressure applied at the time of die bonding (at the time of attaching the chip), as shown in FIG.
A gap is created between the film 7 and the film 7. All of these problems of area and gap are not preferable because they cause package cracks after the product is manufactured.

Therefore, most recently, studies have been conducted to cut off unnecessary film between the leads 9a. For example, FIG. 4A shows an example of a LOC lead frame for a DRAM, but a bus bar 9b is provided inside the lead 9a in order to shorten the wiring length and speed up the access time. For this reason, the punching film 7 is required to have a complicated shape (comb shape) traced along the periphery of the lead in the area necessary for fixing the chip. In this case, the used area of the film is minimized, and as shown in FIG.
As shown in (B), the film gap problem due to pressure during die bonding does not occur.

[0007]

As described above, in the conventional device, the film to be attached to the lead frame has a complicated shape. Therefore, the following problems occur in the process of attaching the film to the lead frame. Was newly born.

(1) If the physical properties of the film to be used vary, or if the punched-out film has a complicated shape, fibrous burrs often occur at the cut end of the film, greatly impairing productivity. . That is, as shown in FIG. 5, when the burr 18 generated during punching adheres to the bonding surface at the tip of the lead 9a or the tip of the capillary 16 of the wire bonder, the wire is not crimped or the capillary is clogged. Cause bonding failure.

(2) A semiconductor package is assembled by mounting a Si chip on a highly accurately processed lead frame. However, in a lead frame with an adhesive such as LOC to which a film is attached, a high temperature (about 400 ° C.) is used. After the film is pasted with), hardening starts at the glass transition temperature Tg (about 250 ° C), so at room temperature, due to the difference in linear expansion coefficient between the film and the lead frame material, the lead frame is largely warped like a bimetal. In some cases, this may occur, which may hinder the assembly of the semiconductor device.

(3) Since the punching and the sticking of the film are carried out by the same mold, it is necessary to incorporate the heat generating part necessary for sticking and forced water cooling, which makes the mold shape complicated and expensive.

(4) The same high-temperature drying process is performed not only when the film is attached to the lead frame but also when the chip is attached, so that the lead frame under the chip is warped.

An object of the present invention is to solve the drawbacks of the prior art by improving the sticking property of the film, to eliminate the defective bonding due to the burr generated at the time of punching the film, and to warp the lead frame after sticking the film. It is an object of the present invention to provide a method for attaching a film to a lead frame, which can significantly reduce

Another object of the present invention is to provide a method of attaching a chip to a lead frame, which is capable of greatly reducing the warp of the lead frame after the chip is attached by improving the attachability of the chip. is there.

[0014]

The present invention provides a method for attaching a film to a lead frame, wherein an insulating or conductive film is attached to the lead frame via an adhesive, and the film is attached to the surface to be attached with the adhesive. After applying, punch out into a predetermined shape with a die, swell and dissolve the adhesive applied to the adhered surface of the punched film with a solvent, and attach the above film to the lead frame through the swelled and dissolved adhesive After attachment, it was dried at a low temperature around 100 ° C.

The present invention also provides a method for attaching a chip to a lead frame, wherein a semiconductor chip is attached via an adhesive applied to the adhered surface of an insulating or conductive film attached to the lead frame. The adhesive applied to the surface to be adhered is swollen and dissolved with a solvent, the semiconductor chip is attached to the lead frame via the swollen and dissolved adhesive, and the adhesive is dried at a low temperature around 100 ° C. Is.

In these cases, a thermoplastic or thermosetting adhesive or the like can be used as the above-mentioned adhesive, and a known solvent for swelling and dissolving them can be used as the solvent.
In particular, when polyether amide imide is used for the adhesive, the solvent is preferably NMP in which swelling and dissolution start in a short time.

[0017]

When the film is punched into a predetermined shape with a die, fibrous burrs are generated from the cut end of the film. However, when the surface to be adhered of the film coated with the adhesive is immersed in a solvent tank, the adhesive swells and dissolves by the solvent, so that the burr is dissolved and removed at this time. The remaining adhesive is viscous and ready for direct bonding even at room temperature.

In this state, the film is pressed and attached to the lead frame. After sticking, when drying is performed at an ambient temperature of about 100 ° C. and the bonding is completed, since the temperature difference from room temperature is small, even if there is a difference in linear expansion coefficient between the film and the lead frame material, warpage does not occur in the lead frame. Even if it occurs, it is extremely small.

On the lead frame with the film attached,
Also when the semiconductor chip is attached with the adhesive applied to the film surface, it can be attached by the same method as the above-mentioned attachment of the film, and the lead frame is not warped.

[0020]

EXAMPLES Examples of the present invention will be described below. Figure 1
It is process drawing which shows the Example of the film sticking method to the lead frame for LOC. With regard to the film sticking die, the conventional example in which punching and sticking were performed using the same die (Fig. 2
(See), punching and pasting are done in different molds and stages.

That is, the punching die is a punching method from the bottom, not from the top, in transporting the film, and is provided with a punch 1, a stripper 3 and a die 2, but a heater block for sticking is provided on the die 2. Absent. Instead, a die suction collet 23 is used to convey the punched film 8 (FIG. 1A). In addition, the bonding stage includes two heat blocks 5 and 5 which are vertically opposed to each other and is controlled to a low ambient temperature of about 100 ° C. (FIG. 1 (E)).

Now, an adhesive-attached polyimide film 7 coated with polyetheramideimide on both sides as an adhesive
Is prepared and supplied to a fixed position of the punching die (FIG. 1 (A)), the film 7 is punched into a predetermined shape by the punch 1, and the punched film 8 is adsorbed by the collet 23 (FIG. 1 ( B)).

The adsorbed film 8 is directly conveyed as a solvent 24 onto a solvent tank 25 containing NMP or the like, and only the adhered surface to be attached to the lead frame 9 is brought into contact with the solvent 24 to swell and dissolve the surface of the adhesive. (FIG. 1 (C)). The reason why only the adhered surface is brought into contact is that the film is not damaged. In the experiments, the inventors confirmed that when the adhesive is a polyether amide imide, when it is immersed in NMP, the surface of the adhesive layer becomes viscous after about 10 seconds and can be bonded at room temperature in about 20 seconds. ing.

Next, the collet 23 is transferred to a predetermined position on the lead frame 9 while the film 8 is adsorbed, and the film 8 is pressed against the lead frame 9 with a viscous adhesive (FIG. 1 (D)). Then, it is transferred between the heat blocks 5 on the attaching stage and dried at a low ambient temperature of about 100 ° C. to complete the adhesion (FIG. 1 (E)).

As described above, according to this embodiment, only the adhered surface of the punched film 8 is brought into contact with the solvent 24 to swell and dissolve the adhesive before sticking to the lead frame. Since burr also swells and dissolves together, burr generation can be ignored. This is a great advantage because it is not necessary to consider a burr countermeasure when punching out a complicated film shape in which burr is particularly often generated. Therefore, it is possible to eliminate wire crimping defects due to the burr 18 that must be absolutely prevented in the lead frame manufacturing process and bonding defects due to capillary clogging.

Further, according to this embodiment, since the film is pressed against the lead frame and then dried at a low temperature of about 100 ° C. at most, the film is stuck at a high temperature of about 400 ° C. and then at the glass transition temperature Tg. Unlike the conventional process in which the curing is started, the warp due to the difference in the linear expansion coefficient of the material does not occur in the lead frame even at room temperature, and the assembly of the semiconductor device becomes smooth.

Further, since punching and pasting are performed separately and the heat generating portion and the forced water cooling mechanism are eliminated from the punching die, the die shape is simple and the cost can be reduced.

By the way, in the above embodiment, the method of attaching the film to the lead frame has been described.
The same applies to the case where a semiconductor chip is mounted on the lead frame. This is because the leads and the chips are attached to each surface of the adhesive-coated film whose both surfaces are coated with the adhesive. For chips,
Therefore, only the adhered surface of the film that is the chip attachment surface attached to the lead frame is immersed in a solvent to swell and dissolve the applied adhesive, and the semiconductor chip is attached to the lead frame through the dissolution and dustproof adhesive. Stick it in place. After attachment, if the same low temperature drying is performed at around 100 ° C., the lead frame under the chip does not warp.

When the punched film is dipped in a solvent, if not only one side but also both sides of the film are dipped,
Since the chip can be continuously attached to the lead frame after the film is attached to the lead frame, the lead frame can be easily manufactured. In the above embodiment, L
Although the lead frame for OC has been described, the present invention uses C
It can also be applied to an OL lead frame. The film attached to the lead frame is not limited to the insulating layer (polyimide film) and may be a conductive film. Further, Haimaru (manufactured by Hitachi Chemical Co., Ltd.) can be used as the thermoplastic adhesive.

Further, although the punching die is a punching method from the bottom, it may be a punching method from the top as in the conventional case. In that case, it is preferable to use the coating method instead of dipping the solvent.

[0031]

EFFECTS OF THE INVENTION (1) According to the invention described in claim 1, since the temperature of the film after drying is about 100 ° C. after attachment of the film, the warp of the lead frame due to the difference in linear expansion between the materials is extremely small. . In addition, since burrs generated during punching of the film swell and dissolve, burrs can be ignored in the work. Therefore, the sticking workability and the bonding property are remarkably improved and the reliability is excellent.

(2) According to the second aspect of the present invention, even when the chip is attached, the temperature of the lead frame during drying is around 100 ° C., so that the warp of the lead frame due to the difference in linear expansion of the material is extremely small.

(3) According to the invention described in claim 3, since the polyether amide imide is used as the adhesive and the adhesive is immersed in NMP, it is possible to create a state in which the adhesive can be adhered in a short time. , Work efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a work process diagram illustrating an embodiment of a method for attaching a film to a lead frame of the present invention.

2A and 2B are schematic cross-sectional views of a mold device for explaining a conventional method of attaching a film of a LOC package, wherein FIG. 2A is an explanatory diagram before attaching the film, and FIG. 2B is an explanatory diagram after punching and attaching the film.

3A and 3B are explanatory views showing a film pasting state of a conventional LOC package lead frame, FIG. 3A is a plan view of the film pasting state, and FIG. 3B is a sectional view showing a film deformed state at the time of die bonding.

FIG. 4 is an explanatory view showing a pasted state of a film of a conventional improved LOC package lead frame,
(A) is a plan view of a film attached state in which the inter-lead film is cut off, and (B) is a sectional view showing the film attached state at the time of die bonding.

FIG. 5 is an explanatory view showing a defect situation at the time of conventional wire bonding.

[Explanation of symbols]

 1 Punch 2 Die 3 Stripper 5 Heat Block 7 Film 8 Punched Film 9 Lead Frame 23 Collet 24 Solvent 25 Solvent Tank

Claims (3)

[Claims] 1. A method of sticking a film to a lead frame via an adhesive, comprising: applying the adhesive to a surface to be adhered of the film; then punching the film into a predetermined shape by a die and punching. The adhesive applied to the adhered surface of the film is swollen and dissolved with a solvent,
A method of sticking a film to a lead frame, which comprises sticking the film to a lead frame via the swelling-dissolved adhesive, and drying the film at a low temperature around 100 ° C. after sticking. 2. A chip attaching method to a lead frame, wherein a semiconductor chip is attached via an adhesive applied to an adhered surface of a film attached to a lead frame,
The adhesive applied to the surface to be adhered of the film is swollen and dissolved with a solvent, the semiconductor chip is attached to the lead frame via the swollen and dissolved adhesive, and after the attachment, 100
A method of attaching a chip to a lead frame, characterized in that it is dried at a low temperature around ℃. 3. The method of attaching a film to a lead frame according to claim 1, wherein the adhesive is polyether amide imide and the solvent is N-methylpyrrolidone (NMP). The method of attaching the chip to the lead frame described in.