JP2746062B2 - How to attach film to lead frame - Google Patents

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 by attaching an insulating or conductive film with an adhesive or a film composed of only an adhesive (hereinafter referred to as a film) to a lead frame. Especially,
The present invention relates to a method for attaching a film to a lead frame, which can stably provide a good attached state of a film even if the properties of the film with an adhesive differ.

[0002]

2. Description of the Related Art A COL (Chip O
Adhesives (thermoplastic and thermosetting adhesives, etc.) are previously applied to one or both sides of a high heat-resistant polyimide film for mounting semiconductor chips on lead frames with n Lead) or LOC (Lead on Chip) structures. There is a film that has been put into practical use as a prefabricated lead frame by attaching a film with an adhesive.

[0003] When a film is to be attached to such a lead frame, for example, a film attaching device as shown in FIG. 5 is used.

[0004] This film sticking apparatus cooperates with a die 5 to punch and shear the film 2 into a predetermined shape.
And a heater block 6 for heating the lead frame 1 to a predetermined temperature, and a stripper 4 for peeling the punched film 2 from the punch 1. After punching and shearing the located film 2 into a predetermined shape with a punch 3,
As shown in FIG. 6, the punched film 2 is lowered as it is, and is pressed against the heat block 6 together with the lead frame 1 thereunder, whereby the film 2 is adhered to a predetermined position of the lead frame 1 by thermocompression bonding. In this thermocompression bonding method, when the film 2 is pressed against the lead frame 1, a constant pressure bonding method in which the heater block 6 is pressed at a constant pressure from below is employed.

[0005]

However, according to the conventional method of attaching a film to a lead frame, the viscosity of the adhesive at a high temperature is not constant due to the manufacturing conditions of the adhesive of the film to be used. There is a problem that variation occurs. To prevent this problem,
Pressure conditions had to be set for each production lot of film. For example, in the case of a thermoplastic adhesive, its molecular weight and glass transition temperature have a large effect on the viscosity at high temperature. Due to the required characteristics of the film used for the package, it is necessary to increase the viscosity at high temperature (glass transition temperature) as much as possible. Therefore, it is considered that it is extremely difficult to control the molecular weight at the time of producing a film.

Accordingly, the problems can be arranged as follows. (1) Since the viscosity at high temperature differs greatly depending on the manufacturing conditions of the adhesive used for the film or the inherent physical properties of the varnish,
Variations occur in the state of adhesion, making quality control of the product difficult. Further, in order to obtain a stable bonding state, the pressure condition must be set each time depending on the film production lot. (2) In the film composed only of the adhesive layer, the residual thickness of the film at the affixed part varies, and the electrical characteristics (insulation)
May be damaged. (3) If the thickness of the film bonding part varies, the vertical position of the chip in the package will vary if assembled as a package. In this case, the tolerance is lost, which causes chip exposure.

[0007] Accordingly, an object of the present invention is to attach a film to a lead frame which can provide a sound adhesion state without complicated work and facilitate product quality control even if the film characteristics are different. Is to provide a way.

Another object of the present invention is to provide a method of attaching a film to a lead frame, which can keep the remaining thickness of a film composed of only an adhesive layer constant.

Still another object of the present invention is to provide a method for attaching a film to a lead frame, which can stabilize the vertical position of a chip in a package by eliminating variations in the thickness of a film bonding portion. is there.

[0010]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides a sound bonding state without complicated work and facilitates quality control of products, even if the film characteristics are different. In order to stabilize the vertical position of the chip in the package, the remaining thickness of the film composed of only the adhesive layer can be made constant, and furthermore, the thickness of the film bonding portion can be made uniform and the vertical position of the chip in the package can be stabilized. by controlling the amount of vertical displacement of the punches, always with an adhesive film-
Reduce it by a certain thickness and crush it.
There is provided a film sticking method to the lead frame so as to bond the attached adhesive film to the lead frame. That is, the present invention provides a method for attaching a film to a lead frame based on displacement control instead of conventional pressure control.

The predetermined thickness is most preferably about 3 to 5 μm. This is because if it is less than 3 μm, a partial non-adhered portion occurs, and if it is more than 5 μm, it is excessively pushed by the adhesive layer and peeled off.
In other words, when the bonding pressure is released, the rapidly softened adhesive flows in the adhesive layer around the lead where the surface pressure is higher than the central part of the lead, hardens during the flow, and a vacuum is applied to this part. This is because voids are formed. In particular, peeling due to excessive pushing may remain even after the package is sealed with a resin, and absorption of moisture causes a package crack, so that it must be prevented during manufacturing. When bonding the lead frame to the lead frame, the heater presses the lead frame at a constant pressure from below, that is,
When the constant pressure bonding method is used together, a more stable bonding state can be secured.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for attaching a film to a lead frame according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an apparatus for attaching a film to a lead frame applied to the present invention. In this figure, the same parts as those in FIG. 5 are denoted by the same reference numerals, and a duplicate description will be omitted.

The apparatus for attaching a film to a lead frame is connected to an air cylinder 10 for raising and lowering the punch 3, an air cylinder 11 for raising and lowering the heater block 6, and air cylinders 10 and 11 via valves 8 and 9. The apparatus includes a pneumatic pressure source 7, a displacement sensor 13 for detecting the amount of downward displacement of the punch 3 after coming into contact with the lead frame 1, and a control unit 12 for controlling the air cylinders 10 and 11 through valves 8 and 9.

As described above, the displacement sensor 13 detects the amount of downward displacement of the punch 3 from the contact with the lead frame 1,
That is, the crushing amount (thickness) of the film 2 is detected.

The control unit 12 controls the air cylinders 10 and 11 through the valves 8 and 9. The control of the valve 8 raises and lowers the punch 3, and the control of the valve 9 controls the heater block 6 from below. Pressing force, that is, while controlling the sticking pressure constant,
When the crushing amount of the film 2 detected by the displacement sensor 13 reaches a preset value (3 to 5 μm), the valve 8
To stop the lowering of the punch 3 by controlling the air cylinder 10.

Hereinafter, a method for attaching a film to a lead frame according to the present invention will be described with reference to the flowchart of FIG.

First, prior to the lowering of the punch 3, the heater block 6 is raised by the air cylinder 11 to heat the lead frame 1 to a predetermined temperature. Next, the air cylinder 10 is operated to lower the punch 3, and the film 2 is punched and sheared into a predetermined shape by the cooperation of the punch 3 and the die 5, and then the film 2 punched to the lead frame 1 below the die 5. Is pressed down to contact a predetermined position of the lead frame 1.

When the punch 3 is further pushed down, the film 2 is crushed by the lead frame 1 as shown in FIGS. 3 and 4, and the thickness of the adhesive layer 12 formed on the surface of the base film 2 is reduced. The amount of crushing δ is reduced and the adhesive layer 12
Protrudes over the width b. Film 2 crushing amount δ
Is detected by the displacement sensor 13, and when the crushing amount δ reaches a predetermined thickness (3 to 5 μm), the control unit 12 controls the air cylinder 10 through the valve 8 to lower the punch 3. To stop. The film 2 and the lead frame 1 punched out by the downward movement of the punch 3 are pressed into the heater block 6 and sandwiched, so that the film 2 is adhered to a predetermined position of the lead frame 1 by thermocompression.

Here, the reason why the crushing amount δ is set to about 3 to 5 μm is that if the crushing amount is smaller than 3 μm, a partial unbonded portion occurs. When the application pressure was released, the rapidly softened adhesive flowed in the adhesive layer around the lead where the surface pressure was higher than the central part of the lead, hardened during the flow, and a vacuum gap Because it can be. Excessive peeling may remain even after the package is sealed with a resin. Absorption of moisture may cause cracking of the package and must be prevented during manufacturing.

The use of the width b of the adhesive layer 12 protruding from the periphery of the lead frame 1 makes it possible to easily manage the state of affixed products.

In the present invention, the displacement of the punch is detected to control the bonding state.
Furthermore, it is possible to secure a stable attachment state,
Abnormalities in film physical properties can also be detected.

Further, by applying a vertical exciting force to the force for pressing to a predetermined displacement, the fluidity of the adhesive at a high temperature can be promoted, and the stabilization of the bonding can be achieved, and the bonding time can be improved. Can be shortened.

The present invention is not limited to affixing a film to a lead frame having a LOC / COL structure.
The present invention can also be applied to attaching a lead fixing tape.

[0025]

As described above, according to the method for affixing a film to a lead frame according to the present invention, the amount of vertical displacement of the punch is controlled in order to eliminate variations in the vertical position of the chip in the package. In this way, the adhesive-attached film is crushed so as to reduce by a predetermined thickness and adhered to the lead frame, so that even if the film characteristics are different, a sound adhesive state can be obtained without performing complicated work. In addition, the quality control of the product can be facilitated, the remaining thickness of the film composed only of the adhesive layer can be kept constant, and the thickness of the film bonding portion can be made uniform, and the vertical position of the chip can be reduced. Can be stabilized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a film sticking apparatus applied to the present invention.

FIG. 2 is a flowchart showing one embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a bonded state of a film according to one embodiment.

FIG. 4 is a top view showing a bonded state of a film according to one embodiment.

FIG. 5 is a sectional view showing a conventional film sticking apparatus.

FIG. 6 is a sectional view showing a conventional film sticking apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Lead frame 2 Film 3 Punch 4 Stripper 5 Die 6 Heater block 7 Pneumatic source 8, 9
Valve 10, 11 Air cylinder 12 Control unit 13 Displacement sensor

Claims (3)

(57) [Claims] 1. A lead for punching an insulating or conductive film with an adhesive positioned on a die into a predetermined shape with a punch, and bonding the film to a predetermined position of a lead frame on a heater positioned below the die. In the method of attaching a film to a frame, by controlling the amount of vertical displacement of the punch,
Always reduce the film with adhesive by a certain thickness
A method for attaching a film to a lead frame, wherein the film with the adhesive is adhered to the lead frame by crushing . 2. The method according to claim 1, wherein said predetermined thickness is about 3 to 5 μm. 3. The method for attaching a film to a lead frame according to claim 1, wherein when the film with adhesive is adhered to the lead frame, the heater presses the lead frame from below under a constant pressure.