JPH11289151A - Surface protection layer forming method for circuit substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately form an aperture part without deviations on a surface protective layer, for the purpose of connecting an electronic component, a connector and the like. SOLUTION: This surface protection layer 7 of a circuit substrate is formed while a part of a resist layer 3, to be used for formation of a circuit wiring pattern 2A, is used as a mask 5A for an aperture part 6 of the surface protective layer 7 used for the circuit wiring pattern 2A. An exposure mask 4 for exposing the resist layer 3 is formed in such a manner that the light transmittance of the part corresponding to the aperture part 6 of the surface protection layer 7 and the light transmittance of the part corresponding to the circuit wiring pattern 2A are different.

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 circuit board, such as a flexible circuit board, which does not shift an opening provided in a surface protective layer for connecting electronic components, connectors and the like on the circuit board. The present invention relates to a method for forming a surface protective layer on a circuit board for accurate formation and an exposure mask used for the method.

[0002]

2. Description of the Related Art In recent years, as electronic equipment has become higher in density and smaller in size, the structure of a circuit board to be used has not only been reduced to a fine pattern of circuit wiring patterns, but also to a higher density as a whole mounted circuit board. There is a demand for miniaturization and miniaturization, and accordingly, the number of electronic components such as LSIs and chips mounted on one circuit board, the number of connectors and the like, and the like are increasing.

For this reason, a circuit board having a large number of openings as a land for electronic parts and a land for connectors is required for a surface protective layer commonly called a cover material. In particular, the flexible circuit board has a thinner material than other boards and a better heat dissipation, so the circuit board for high current capacity,
It is drawing attention as a circuit board for heat dissipation when mounting high-density components.

Further, since the flexible circuit board is made of a film material, it can be used in a bent state. It has been put to practical use as a circuit board integrated with a cable or a cable.

A surface protective layer as a cover material used for a general flexible circuit board includes a cover film and a cover.
There are two types of coats. The cover film is formed of a film of an insulating material provided with an adhesive component. As a method of forming the opening, a film type in which the opening is formed in advance by a mold or the like before bonding with the base material, There are two types of exposure types, in which a photosensitive film is used for the cover film, which is bonded to a base material, and then exposed and developed through a light shielding mask to form an opening.

On the other hand, the cover coat is made of a solution of an insulating material provided with an adhesive component, and the opening is formed by a printing method using a screen printing machine or the like and a cover provided with a photosensitive component. There are two types of exposure types, in which a coating material is applied to a base material by a curtain coating method or the like, and is exposed and developed through a light shielding mask to form an opening.

[0007]

The following problems occur in the method of forming the surface protective layer as a general cover material in accordance with the above-mentioned demand for high density. First, in the case of a cover film, as the demand becomes higher, a high-density die and a punching device are required to form the opening, so that the cost becomes high and the die cost increases.

Further, when bonding with a base material, a guide hole formed in the material is inserted and temporarily fixed to a guide rod provided in the bonding machine, so that the opening of the cover and the design position are adjusted according to the accuracy of both. A gap occurs between them. Then, there is a melt out of the adhesive component due to heat and pressure at the time of bonding,
This also causes a deviation between the area of the opening of the cover and the design area.

An exposure type cover film requires an exposure mask, which must be manufactured at a correction rate corresponding to the etching shrinkage rate of the base material, and the base material has a variation in shrinkage rate. In some cases, a deviation from the design value of the opening occurs. In addition, a deviation occurs when the exposure mask is fixed, and a deviation between a cover opening formed by exposure and development processing and a design value occurs. Further, since a photosensitive component is added to the material, the cost of the material is higher than that of a general cover film material.

On the other hand, in the case of a cover coat, a deviation occurs between the cover opening and the design position in accordance with the accuracy of the guide holes of the printing press. In addition, since the solution has a low viscosity, a flow such as bleeding occurs, and a gap between an opening area of the cover and a design area occurs.

Since the exposure type cover coat also requires an exposure mask as in the case of the film, even in this case, it is necessary to manufacture the exposure type at a correction rate corresponding to the etching shrinkage rate of the base material. If the base material has a variation in shrinkage, a deviation from the design value of the opening occurs. Also,
Since a shift occurs when the mask is fixed, a shift occurs between the cover opening formed by the exposure and the development processing and the design value. Further, since a photosensitive component is added to the material, the cost of the material is higher than that of a general cover coat material.

In view of the above, according to the present invention, when fabricating a circuit board such as a flexible circuit board, an opening provided in a surface protective layer for connecting electronic components and connectors on the circuit board can be accurately formed without displacement. An object of the present invention is to provide a method for forming a surface protective layer on a circuit board to be formed and an exposure mask for use in the method.

Also, the present invention provides a method for forming an opening using a photosensitive cover material and a method for forming a surface protective layer by bonding a cover film having an opening with a high-precision mold. It has an extremely excellent opening structure that eliminates the deviation from the design value of, and furthermore, the material cost is lower than that of the photosensitive cover material, and the total processing cost is lower than that of the mold production. The present invention provides a method of forming a surface protective layer on an inexpensive and extremely excellent circuit board, and an exposure mask for use in the method.

[0014]

Therefore, in the method of forming a surface protective layer on a circuit board according to the present invention, when a circuit board is manufactured, a resist layer used for forming a circuit wiring pattern is manufactured. The present invention is characterized in that a surface protective layer of a circuit board is formed while a part thereof is diverted to a mask for an opening of the surface protective layer for the circuit wiring pattern.

Here, a photosensitive resist may be used for the resist layer, a polyimide varnish may be used for the surface protective layer, and an exposure mask for exposing the resist layer may include the surface resist. By using a material having a different light transmittance from the portion corresponding to the opening of the protective layer and the portion corresponding to the circuit wiring pattern, the surface protection under a predetermined resist peeling condition is performed. A part of the resist layer can be left as a mask at a portion corresponding to the opening of the layer.

An exposure mask for exposing the resist layer has a light transmittance of a portion corresponding to an opening of the surface protective layer and a light transmittance of a portion corresponding to a circuit wiring pattern. Use a differently formed one.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in further detail with reference to the illustrated embodiments. In the present invention, when a circuit board is manufactured by an etching method, a part of the resist layer used for forming a circuit wiring pattern is diverted to a mask for an opening of a surface protective layer as a cover material. In this way, the present invention has been devised so that deviation from the design value of the opening in the formation of the surface protective layer can be eliminated.

In this case, a photosensitive resist can be used for the resist layer, and a polyimide varnish can be used for the surface protective layer. However, if both have a function as a mask layer and a surface protective layer, they can be used. Can also be used as appropriate.

Here, a general exposure mask is used in which the light transmittance of a portion where a conductive layer such as a copper foil is etched is different from the light transmittance of a portion corresponding to a circuit wiring pattern. Instead, a material is prepared in which the light transmittance of the portion corresponding to the opening of the surface protective layer is different from the above light transmittance.

By exposing the resist layer at a predetermined exposure amount using this exposure mask, the exposure processing of the circuit wiring pattern forming portion and the surface protection of the circuit wiring pattern forming portion having different exposure amounts are performed. Exposure processing of the opening of the layer can be performed at a time, and thereby, the deviation between the opening of the surface protective layer and the opening at the designed value can be eliminated.

Then, the resist region of the etched portion is peeled off by the developing process, and the exposed conductive layer portion is removed by etching, so that a circuit wiring pattern can be formed. Under a certain resist stripping condition, the mask for forming the circuit wiring pattern is stripped, but the resist in the opening of the surface protection layer having a different exposure amount remains. It is diverted to a part of the mask.

In this state, polyimide varnish or the like as a material of the surface protective layer is thinned in the opening of the surface protective layer by using a screen printing machine, a curtain coat or a bar coater. After coating the entire surface and drying it, the resist portion remaining as a mask in the opening of the surface protective layer under conditions different from the above-mentioned resist peeling is removed, so that the deviation from the design value is eliminated. Can be formed, so that a surface protection layer for a circuit board can be finally formed by adding a curing process.

FIGS. 1 (1) to 1 (7) are views showing one manufacturing process thereof. First, as shown in FIG. 1 (1), an adhesive is used for a suitable flexible insulating base material 1. An adhesive-free copper-clad laminate composed of a copper foil 2 as a conductive layer without any lamination was prepared, and a dry film type photosensitive resist layer 3 was heated to 90 ° C. on the copper foil 2 by a roll laminator. Were used for uniform bonding.

Therefore, an exposure mask 4 was fixed on the photosensitive resist layer 3 as shown in FIG. This exposure mask 4
Are a non-exposed area 4A for shielding the portion where the copper foil 2 is etched, a semi-exposed area 4B for shielding the portion corresponding to the opening of the surface protection layer, and a whole exposed area 4C for forming a circuit wiring pattern. It consists of.

Next, as shown in FIG. 3C, a portion where the copper foil 2 is etched by using an exposure machine has an unexposed portion 3A,
A semi-exposed portion 3B is provided at a portion corresponding to the opening of the surface protection layer
Exposure treatment was applied to the portions where the circuit wiring pattern is to be formed so as to form the entire exposed portion 3C.

At this point, as shown in FIG. 4D, the photosensitive resist layer 3 in the unexposed portions 3A is removed by developing using a 1% aqueous sodium carbonate solution, and then using an aqueous copper sulfate solution. The exposed portion of the copper foil 2 was removed by etching to form a required circuit wiring pattern 2A. Furthermore, 0.25
A portion of the photosensitive resist layer 3 in the entire exposed portion 3C is removed by using a sodium hydroxide solution.
B remains as a mask for the opening of the surface protection layer. As a result, the formation of the circuit wiring pattern 2A and the semi-exposed portion 3B as a mask for the opening of the surface protection layer can be formed simultaneously.

Next, as shown in FIG. 5 (5), a polyimide varnish solution was used as a material for the surface protective layer using a coating machine so that the thickness of the polyimide varnish solution was about 10 μm after being vapor-phase dried over the entire surface. The varnish layer 5 was entirely coated. At this time, the thickness of the polyimide varnish at the portion 5A of the semi-exposed portion 3B functioning as a mask is appropriately reduced.

Therefore, as shown in FIG.
When the semi-exposed portion 3B functioning as a mask is removed together with the polyimide varnish of the portion 5A formed thin with a sodium hydroxide solution, an opening 6 in which a part of the circuit wiring pattern 2A is exposed can be formed.

Finally, 2 is applied to the remaining polyimide varnish layer 5.
By performing the heat treatment at 70 ° C. for a required time, a surface protective layer 7 having an opening 6 having excellent electrical properties and weather resistance and having no deviation can be formed as shown in FIG.

[0030]

According to the present invention, it is possible to stably provide a circuit board in which a difference between a design value and an opening to be formed in a surface protective layer can be provided. Compared with the method of forming the opening of the protective layer or the method of forming the opening using the photosensitive cover material, the surface protective layer having the accurate opening can be formed at low cost.

By adopting the present invention, 1
Circuit boards with many openings in the surface protection layer can be manufactured and provided at high quality and at low cost as land for chip parts and land for connectors for mounting a large number on one circuit board. Thus, a circuit board having extremely excellent cost performance can be stably provided.

[Brief description of the drawings]

1 (1) to 1 (7) are manufacturing process diagrams according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flexible insulating base material 2 Copper foil 2A Circuit wiring pattern 3 Photosensitive resist layer 3B Semi-exposure part as a mask 4 Exposure mask 5 Polyimide varnish layer 6 Opening 7 Surface protective layer

Claims (4)

[Claims] When manufacturing a circuit board, a part of a resist layer used for forming a circuit wiring pattern is diverted to a mask for an opening of a surface protection layer for the circuit wiring pattern. Forming a surface protection layer on the circuit board while forming the surface protection layer on the circuit board. 2. A photosensitive resist is used for the resist layer,
2. The method for forming a surface protective layer on a circuit board according to claim 1, wherein a polyimide varnish is used for the surface protective layer. 3. An exposure mask for exposing said resist layer has a light transmittance of a portion corresponding to an opening of said surface protective layer and a light transmittance of a portion corresponding to a circuit wiring pattern. Wherein a part of the resist layer is left as a mask at a portion corresponding to an opening of the surface protective layer under a predetermined resist stripping condition by using a different resist. The method for forming a surface protective layer on the circuit board according to the above. 4. An exposure mask for exposing the resist layer has a light transmittance of a portion corresponding to an opening of the surface protective layer and a light transmittance of a portion corresponding to a circuit wiring pattern. An exposure mask for forming a surface protective layer on a differently formed circuit board.