JPH07153797A - Bump of circuit board and manufacturing method of it - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing bumps of a uniform shape stably and bumps formed by this method. CONSTITUTION:A solution of polyimide resin is applied on a copper foil conductor 3 of EPC1 and a polyimide layer 4 is formed by curing the polyimide resin. A hole 5 is formed in the polyimide layer 4. A bump 6 is formed in the hole 5 of the polyimide layer 4 by electroplating of solder. As plating liquid does not act on the polyimide layer 4, the bump 6 is formed only inside the hole 5 of the polyimide layer 4 in a specified form. The bump 6 is kept protruding from the polyimide layer 4. With this, the bump 6 is mated with an electronic component easily and a terminal of the electronic component is soldered reliably by heat melting the bump 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bump of a circuit board for connecting an electronic component to a conductor of the circuit board and a method for manufacturing the bump.

[0002]

2. Description of the Related Art As is well known, metal bumps are formed in advance on a conductor of a circuit board, terminals of electronic parts are butted against the bumps, and the bumps are heated and melted, whereby terminals of the electronic parts are fixed. There is a method of connecting.

To form this bump, for example, as shown in FIG.
As shown in (a), a polyimide film 15 is laminated on a flexible substrate 13 composed of a polyimide film 11 and a copper foil conductor 12 via an adhesive layer 14, holes 16 are formed in the polyimide film 15, and then electric soldering is performed. Plating. As a result, solder bumps 17 are formed in the holes 16 of the polyimide film 15 as shown in FIG.

[0004]

However, since the adhesive layer 14 deteriorates during the pretreatment of the electric solder plating or during the treatment, the adhesive force of the adhesive layer 14 may be lowered. In this case, the plating solution is polyimide film 1
It has been found by research and study that the solder plating penetrates under the holes 5 and penetrates not only into the holes 16 but also around the holes 16, which causes defective bump shape.

Although solder plating is exemplified here, bumps may be formed by gold plating or silver plating. In the case of gold plating or silver plating, bump shape defects occur due to the same reason as solder plating.

Therefore, an object of the present invention is to provide a method for stably manufacturing a bump having a uniform shape, and a bump formed by this method.

[0007]

In order to solve the above-mentioned problems, the manufacturing method according to claim 1 of the claims is to apply a solution of a polyimide resin to a circuit board and to cure the polyimide resin, A step of forming a polyimide layer covering the conductor of the circuit board, a step of forming a hole reaching the conductor of the circuit board in the polyimide layer, a bump that grows on the conductor of the circuit board and protrudes from the polyimide layer by metal plating Forming a hole in the layer.

Further, the bumps of the circuit board according to claim 2 are formed by the manufacturing method according to claim 1, and are directly applied to the conductor on the circuit board. It is formed in the hole of the polyimide layer, is connected to the conductor of the circuit board, and protrudes from the polyimide layer.

[0009]

According to the manufacturing method of the first aspect, the solution of the polyimide resin is applied to the circuit board to form the polyimide layer, the polyimide layer is perforated, and then the metal plating is performed. Bumps are formed in the holes of the polyimide layer. Since the polyimide layer is not deteriorated by metal plating and is not attacked by the plating solution, bumps having a predetermined shape are stably formed in the holes of the polyimide layer.

Further, since the bump of the circuit board according to claim 2 is formed by the manufacturing method according to claim 1, it has a predetermined shape and does not deform irregularly. Therefore, the bump and the terminal of the electronic component can be accurately brought into contact with each other, the bump can be melted, and the terminal of the electronic component can be reliably connected.

[0011]

FIG. 1 shows an embodiment of a bump manufacturing method according to the present invention. With reference to FIG. 1, a method of manufacturing the bump of this embodiment will be described below.

(Step 1) As shown in FIG. 1A, a flexible printed circuit board (hereinafter referred to as FPC) 1 is formed by laminating a polyimide film 2 and a copper foil conductor 3. This F
A solution of a polyimide resin is applied onto the copper foil conductor 3 of the PC 1 and the polyimide resin is cured to form the polyimide layer 4.

(Step 2) As shown in FIG. 1B, holes 5 are formed in the polyimide layer 4. This hole 5 is for the copper foil conductor 3
Has reached. An excimer laser, for example, may be used to form the hole 5.

(Step 3) The bumps 6 are formed in the holes 5 of the polyimide layer 4 by electric solder plating as shown in FIG.
To form. At this time, since the polyimide layer 4 is not attacked by the plating solution, the bumps 6 are formed only inside the holes 5 of the polyimide layer 4 and have a predetermined shape.

Further, electric solder plating is performed so that the bumps 6 project from the polyimide layer 4. This facilitates abutting of the bumps 6 with the terminals of the electronic component, and when the bumps 6 are heated and melted, the terminals of the electronic component are reliably soldered.

By the way, a plurality of bumps were formed by the manufacturing method of this embodiment, and the heights of these bumps were measured to determine the variations. The results are shown in Table 1.

In order to compare with the bump formed by the manufacturing method of this embodiment, a plurality of bumps are formed by the conventional method shown in FIG. It is shown in Table 1.
Of course, in order to make this comparison accurately, the circuit board by the manufacturing method of this embodiment and the circuit board by the conventional method are
Except for the adhesive layer 14, they are made substantially the same.

In both the manufacturing method of this embodiment and the conventional method, the current density and processing time of the electric solder plating were calculated so that the bump height would be 50 μm. The current density and processing time were set.

[0019]

[Table 1]

As is clear from Table 1, the bumps formed by the manufacturing method of this embodiment have the predicted height and the variation is small. On the other hand, the bumps formed by the conventional method are much lower than the predicted height and have large variations.

[0021]

As described above, according to the present invention, the polyimide layer is directly applied to the conductor of the circuit board, the holes are formed in the polyimide layer, and the bumps are formed in the holes of the polyimide layer by metal plating. Is forming. Since the polyimide layer is not deteriorated by metal plating and is not attacked by the plating solution, bumps having a predetermined shape are stably formed in the holes of the polyimide layer.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a bump manufacturing method according to the present invention.

FIG. 2 is a diagram showing a conventional bump manufacturing method.

[Explanation of symbols]

 1 Flexible Printed Circuit Board 2 Polyimide Film 3 Copper Foil Conductor 4 Polyimide Layer 5 Hole 6 Bump

Claims (2)

[Claims] 1. A step of applying a solution of a polyimide resin to a circuit board and curing the polyimide resin to form a polyimide layer covering a conductor of the circuit board, and forming a hole reaching the conductor of the circuit board in the polyimide layer. And a step of forming bumps that grow on the conductor of the circuit board and project from the polyimide layer in the holes of the polyimide layer by metal plating. 2. A bump of a circuit board formed by the manufacturing method according to claim 1, wherein the bump is formed in a hole of a polyimide layer directly attached to the conductor of the circuit board and connected to the conductor of the circuit board. , Bumps on the circuit board protruding from the polyimide layer.