JPH0936183A - Solder resist and tape carrier for tab - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a TAB tape carrier which is free from warpage and excellent in adhesion to sealing resin by a method wherein solder resist is formed of epoxy resin below a specific value in heat deformation temperature. SOLUTION: Epoxy solder resist whose heat deflection temperature measured through a prescribed measuring method is below 70 deg.C is used. A cured epoxy resist sheet 7 of thickness 0.1mm is formed, wound on a mandrel 13 of 40ϕ, and heated for five minutes in the air. Then, the sheet 7 is made to stand for cooling off, separated from the mandrel 13, and measured to obtain a deformation rate(DR) based on a following formula, DR=(x/t)×100(%), wherein X denotes a distance between a reference plane in contact with the ends of the sheet 7 and the surface center point of the sheet 7, and t is a distance between a reference plane in contact with the ends of the sheet 7 and the surface center point of the sheet 7 when the sheet 7 is wound on the mandrel 13 and 7.5mm long by calculation. Heating temperatures in the air and deformation rates are plotted, and a temperature at which the sheets 7 changes markedly in deformation rate is defined as a heat deformation temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder resist for protecting leads and a TAB tape carrier using the same.

[0002]

2. Description of the Related Art As shown in FIG. 4, a TAB tape carrier 1 has a lead pattern repeatedly formed on a polyimide resin film 4 having a sprocket hole 2 and a device hole 3 formed therein. It has an inner lead protruding to the device hole 3 and connected to the semiconductor chip, and an outer lead connected to an external circuit. Insulating paint is applied to protect the lead pattern on the intermediate lead portions other than the inner leads and the outer leads that do not contribute to the connection. This paint is generally called solder resist 6.

The tape carrier 1 is mounted on a device such as a liquid crystal after connection with a semiconductor chip and after a work called solid stripping for separating each pattern one by one. A problem at the time of this mounting is the warp of the tape carrier shown in FIG. This is because if the warpage is large, precise mounting cannot be performed. The warp is represented by the average value of the distances a and b at each end from the base when the film carrier 1 is placed on a smooth base with the convex side facing downward.

Warp = (a + b) / 2 (1) Warp is generated by applying a solder resist. At present, the solder resist of the tape carrier has an epoxy resin as a main component, and the warp is caused by a difference in thermal expansion between the epoxy resin and the polyimide resin as a base material. The coefficient of thermal expansion of the solder resist is larger than that of the polyimide, and when the solder resist is cured by heat or the resin for sealing the semiconductor chip part is heated and cooled, the solder resist contracts and warps.

Conventionally, the following measures have been taken to prevent warpage.

(1) As the solder resist, a material having the same coefficient of thermal expansion as the polyimide of the film base material, for example, a polyimide coating material is used.

(2) As the solder resist, a material having a remarkably small elastic modulus such as silicone rubber, for example, a silicone rubber material is used.

[0008]

However, the polyimide-based coating material (1) is expensive and can be practically used only for very limited purposes. Also, the rubber-based material of (2) is
Since it does not adhere to the epoxy used as the sealing resin,
A gap is generated between the solder resist and the sealing resin, resulting in a product that is extremely unreliable.

Thus, there is a demand for a solder resist which does not cause warpage and has good adhesiveness to the sealing resin, and in particular, a warpage of 1.0 mm or less is required.

An object of the present invention is to solve the above-mentioned problems of the prior art and to reduce the warp significantly, and for a TAB which has an extremely small amount of warp and can significantly reduce the troubles caused by the warp. To provide a tape carrier.

[0011]

The present invention is an epoxy-based solder resist having a heat distortion temperature of 70 ° C. or less measured by the measuring method shown in FIG.

A sheet sample 7 of cured solder resist having a thickness of 0.1 mm is prepared.

The sheet 7 is wound around the 40φ mandrel 13, and both ends are fixed with the holding tape 8. In that state, it is heated at a predetermined temperature in air for 5 minutes to be cured.

After cooling, the sheet 7 is removed and the deformation rate is calculated by the following equation.

Deformation rate = (x / t) × 100 (%) (2) where x is the distance from the reference plane contacting both ends of the sheet to the center point of the sheet surface t is the time when the sheet is wound around the mandrel, It is the distance from the reference plane that touches both ends of the sheet to the center point of the sheet surface, and the calculated value is 7.5 mm. As shown, the heating temperature of the sheet and the deformation rate are plotted, and the temperature at which the deformation rate changes greatly is taken as the heat deformation temperature. In the illustrated example, 100 ° C. is the heat distortion temperature.

An epoxy-based solder resist is, for example, CCR-232GS under the trade name of Asahi Kaken Co., Ltd.
V, CCR-240GS and the like.

The present invention is also a TAB tape carrier in which the above-mentioned solder resist is applied to leads on a polyimide resin film.

The solder resist used in the present invention can be obtained by mixing an appropriate amount of generally available epoxy, curing agent, flexibility imparting agent and the like. The mixing ratio differs depending on the type of epoxy curing agent used, etc.
A general common sense is acceptable. Of course, when considering the composition, it is necessary to select a material that has a low heat distortion temperature.

The reason why the solder resist is defined as an epoxy resin in the present invention is that the sealing resin is an epoxy resin, and it is the best that the solder resist is also an epoxy resin from the viewpoint of adhesiveness with the epoxy resin.

Further, the heat distortion temperature is defined as 70 ° C. or less at a level where the degree of warpage becomes a problem at 80 ° C., and at a temperature of 60 ° C. or less, no problem occurs.
This is because it can be determined that the vicinity of ℃ is the boundary.

Here, the measurement of the heat distortion temperature was carried out by the above-mentioned measuring method. This method is different from the method defined by JIS and is a method specially developed for solder resist.

When the epoxy-based solder resist whose heat distortion temperature is lowered in this way is applied to the leads on the polyimide resin film, the warp of the TAB tape carrier can be greatly reduced. Also, the adhesiveness with the epoxy resin becomes good.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the present invention will be described below together with comparative examples. Examples 1 to 3 and Comparative Examples 1 to 3 shown in Table 1 in which an appropriate amount of epoxy, a curing agent, a flexibility-imparting agent, etc. are blended.
Various solder resists were prepared. Incidentally, the solder resist which has been mainly used for the tape carrier hitherto corresponds to Comparative Example 3.

[0024]

[Table 1]

The heat distortion temperatures of these solder resists were measured by the above-mentioned measuring method and were as shown in the upper column of Table 1.

Each of these various types of solid resist was applied in a thickness of 50 μm on a lead which was attached to a polyimide resin film with an adhesive layer. The TAB tape carrier and lead pattern used here are shown in FIG. That is,
It has lead patterns repeatedly formed on a polyimide resin film 4 having a sprocket hole 2 on both sides of the film width and a device hole 3 in the center. The lead 5 projects into the device hole 3 and is connected to an unillustrated semiconductor chip.
The outer lead 11 is connected to an external circuit. The solder resist is an inner lead 10 and an outer lead 11.
Other than the above, it is applied to the intermediate lead portion 12 that does not contribute to the connection.

After the solder resist was applied, it was cured by heat, and after heating was completed, the sample portion C for warpage measurement was cut off. The warpage measurement sample portion C is a strip-shaped portion that is offset from the outer lead side of the solder resist 9 applied in a rectangular shape to the inner lead side by a predetermined width.

Specifically, the sample portion C for measuring the warpage is
20 mm lead with 5 mm length and 80 μm width at 0.15 pitch
The parts are arranged in mm, and the thickness of the lead is 35 μm. The widthwise dimension of the solder resist is 20.4 mm, and the resist thickness is 50 μm as described above.

The cut sample portion C was placed on a smooth table and the warpage was measured based on the equation (1). The results are shown in the lower column of Table 1. Conventionally, the solder resist that has been mainly used for a tape carrier has a particularly large heat distortion temperature and a large warp as shown in Comparative Example 3. On the other hand, it can be seen that the warp becomes smaller as the heat distortion temperature decreases.
By using a solder resist having a heat distortion temperature of 70 ° C. or less, the warpage can be suppressed to 1.0 mm or less. Further, since the epoxy resin is used, it is inexpensive and can be used for various purposes. Moreover, since it is the same material as the encapsulating resin material, the adhesiveness is extremely good, and there is no gap between the solder resist and the encapsulating resin, and a highly reliable product can be obtained.

In the present invention, the method for measuring the heat distortion temperature is based on the method described above, but a method for making the critical value clearer, for example, a method for obtaining an inflection point in a plot, or a differential curve is obtained. If there is another method, it is preferable to adopt it.

[0031]

According to the solder resist of the present invention, since the epoxy resist having a low thermal deformation temperature is used, the amount of deformation after curing can be reduced.

According to the TAB tape carrier of the present invention, the lead of the polyimide resin film is coated with the epoxy-based solder resist having a reduced heat distortion temperature, so that the warp is extremely small and the adhesiveness with the sealing resin is small. A good tape carrier can be obtained, and troubles due to warpage and adhesiveness can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a heating temperature and a deformation rate of a solder resist sheet according to an example of the present invention.

FIG. 2 is an explanatory diagram showing a method of measuring a deformation rate according to the present invention.

FIG. 3 shows T representing a sample for warpage measurement performed in this example.
It is a top view of a tape carrier for AB.

FIG. 4 is a plan view of a general TAB tape carrier.

FIG. 5 is an explanatory diagram showing a method of measuring a warp, which is TAB.
It is a longitudinal cross-sectional view of a tape carrier for use.

[Explanation of symbols]

 2 Sprocket hole 3 Device hole 4 Polyimide resin film 5 Lead 7 Solder resist sheet 9 Solder resist 10 Inner lead 11 Outer lead 12 Intermediate lead part 13 Mandrel C Warpage measurement sample part

Claims (2)

[Claims] 1. An epoxy-based solder resist having a heat distortion temperature of 70 ° C. or less measured by the following measuring method. Make a cured 0.1mm thick sheet. The sheet is wrapped around a 40φ mandrel and heated in air for 5 minutes. After cooling, remove the sheet from the mandrel and calculate the deformation rate using the following formula. Deformation rate = (x / t) × 100 (%) where x is the distance from the reference plane contacting both ends of the sheet to the center point of the sheet surface t is the reference contacting both ends of the sheet when the sheet is wound around the mandrel The distance from the surface to the center of the sheet surface, and the calculated value is 7.5 mm. Plotting the heating temperature in air and the deformation rate,
The temperature at which the deformation rate changes greatly is called the heat deformation temperature. 2. A tape carrier for TAB, characterized in that the solder resist according to claim 1 is applied to leads on a polyimide resin film.