JP3236352B2 - Circuit board manufacturing method - 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 of manufacturing a circuit board, and more particularly, to a method of manufacturing a circuit board, wherein thermal damage to the circuit board caused when through-hole processing is performed on the circuit board and decomposition products of an insulating resin are formed on the circuit board. The present invention relates to a method for manufacturing a circuit board, which can prevent adhesion and residue on a circuit board.

[0002]

2. Description of the Related Art Recent advances in the semiconductor industry have led to further reductions in the size and weight of semiconductor elements and semiconductor devices. As a result, circuit patterns on circuit boards on which elements and devices are mounted have become finer. The demand for is increasing. Generally, in order to miniaturize a circuit pattern, it is preferable to reduce the thickness of the circuit pattern layer by plating, vapor deposition, or the like. In addition, forming a through hole or the like on a circuit board having a miniaturized circuit pattern and forming a conduction path for conducting the surface to the front and back surfaces requires a higher height than the conventional mechanical drilling method. A processing method using laser light in the ultraviolet region of energy has been attracting attention as a desirable method.

However, in processing using high-energy ultraviolet laser light, there is a possibility that a circuit board, which is a workpiece, is thermally damaged, thereby oxidizing a circuit pattern or causing a pattern defect. In addition, when a through hole is formed in the insulating resin layer by irradiating the substrate with a laser beam, the insulating resin is decomposed, and the decomposed product is firmly attached to the through hole opening on the substrate surface. It is necessary to remove the objects by means such as washing, which complicates the process and may not be able to be reliably removed.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to solve various problems arising in processing with high-energy ultraviolet laser light in the above-mentioned conventional method for manufacturing a circuit board. No thermal damage,
It is an object of the present invention to obtain a circuit board having high electrical reliability in which no decomposed matter is attached to a substrate surface.

[0005]

The inventors of the present invention have conducted intensive studies to achieve the conventional object, and as a result, prior to laser processing, a cover resin layer for covering and protecting a circuit pattern has been laminated in advance. After that, irradiate the laser light, or protect the circuit pattern with a protective metal layer and then irradiate the laser light, so that the circuit pattern is not damaged and the resin decomposition product does not adhere at all. Was found, and the present invention was completed.

That is, in a first method of manufacturing a circuit board according to the present invention, a step of forming a circuit pattern of a predetermined shape on one or both surfaces of an insulating resin layer; A step of laminating a resin layer, and forming a hole for conducting a high-energy ultraviolet laser beam to a predetermined position of the cover resin layer and the adjacent insulating resin layer from the side where the cover resin layer is formed to conduct the front and back surfaces. The process of
The method includes a step of removing the cover resin layer, and a step of filling the hole with a conductive substance to conduct electricity to the front and back surfaces.

Further, a second method of manufacturing a circuit board according to the present invention comprises the steps of forming a circuit pattern of a predetermined shape on one or both surfaces of an insulating resin layer, and forming a protective metal layer on the circuit pattern. A step of irradiating a high-energy ultraviolet laser beam to a predetermined position of the insulating resin layer from the protective metal layer forming side to form a hole for conducting the front and back surfaces,
Removing the protective metal layer.

Hereinafter, the present invention will be described with reference to the drawings. 1A to 1H are cross-sectional views illustrating each step of an example of the first method for manufacturing a circuit board according to the present invention.

According to the first manufacturing method of the present invention, for example, as shown in FIG. 1A, one or both surfaces of the insulating resin layer 1 are made of gold, silver, copper, nickel, cobalt, or an alloy thereof. A substrate on which a metal conductive layer 2 made of metal is formed is formed, and the substrate is subjected to a known etching method or the like to form a substrate shown in FIG.
As shown in (b), a circuit pattern 12 having a predetermined shape is formed. The conductive layer 2 to be laminated is preferably a metal mainly composed of copper from the viewpoint of electrolytic plating property in a later step, and the insulating resin layer 1 is laminated by casting, crimping, sputtering, vapor deposition, plating or the like. The thickness of the conductive layer 2 or the circuit pattern 12 is 0.01 to 10 μm, preferably 0.1 to 1 μm for forming a fine pattern.
It is preferable to set the thickness to about 0 μm.

Next, as shown in FIG. 1C, the cover resin layer 3 is laminated on the surface of the circuit pattern 12 on which the laser processing is to be performed, and then the cover resin layer 3 and the insulating resin layer 1 adjacent thereto are formed. A predetermined position is irradiated with high-energy ultraviolet laser light to form a hole 4 as shown in FIG. At this time, the surface of the circuit pattern 12 is protected from damage by the cover resin layer 3. In addition, as shown in FIG. 1D, the decomposition product 5 of the insulating resin adheres to the periphery of the opening of the hole 4.

The ultraviolet laser light is light having a high energy wave having an oscillation wavelength in the ultraviolet region, and an excimer laser is preferably used. Irradiation is performed by directly condensing the light on the processed surface or through an appropriate photomask. The diameter of the hole 4 to be formed is usually 15 to 100 μm from the viewpoint of miniaturization of a circuit pattern.
m, preferably about 20 to 50 μm.

Next, as shown in FIG. 1 (e), by peeling off the laminated cover resin layer 3, the protected circuit pattern 12 is exposed and the adhered resin decomposed material is removed. 5 is removed at the same time.

As shown in FIG. 1 (f), the exposed circuit pattern 12 of the circuit board on which the hole 4 for conducting the front and back surfaces is formed is covered and protected by a plating-resistant resist 6, as shown in FIG. After that, as shown in FIG. 1G, the bottom and side surfaces of the hole 4 are exposed by photolithography.

Then, a metal material 7 such as gold, silver, copper, tin, lead, nickel, cobalt, indium, solder, or the like is plated and filled in the hole 4 by electrolytic plating, and FIG.
A circuit board as shown in FIG. FIG.
(H) As shown in FIG.
The connection terminal can be formed by protruding into a bump shape of not less than μm, preferably about 5 to 100 μm, so that electrical connection can be ensured. The hole 4 is not only filled with a metal substance by electroplating, but also by electroless plating or by mechanically injecting and filling a conductive paste formed by dispersing a metal powder in a resin to form a paste. Is also good.

The insulating resin layer 1 and the cover resin layer 3 used in the manufacturing method of the present invention have an electric insulating property, and have a thickness of 1 to 200 μm, preferably 10 to 200 μm in order to form a flexible circuit board. A film having a thickness of about 100 μm is preferable. Examples of the resin that can be used include a polyester resin, an epoxy resin, a urethane resin, a polystyrene resin, a polyethylene resin, a polyamide resin, a polyimide resin, and A
Any thermosetting resin or thermoplastic resin such as BS resin, polycarbonate resin and silicone resin can be used, and these resins can be used for either the insulating resin layer or the cover resin layer. When the insulating resin layer 1 requires flexibility, silicone rubber, urethane rubber,
It is preferable to use an elastic body such as fluororubber, and when heat resistance is required, it is preferable to use a heat-resistant resin such as polyimide, polyethersulfone, or polyphenylene sulfide. It is preferable that the cover resin layer 3 be made of a material that is more soluble in an acid, an alkali solution, or a solvent than the insulating resin layer 1 in order to peel off only the cover resin layer in a later step. The thickness is 0.1 μm or more, preferably 1 μm or more in order to exhibit a cover effect.

FIGS. 2A to 2H are cross-sectional views illustrating the steps of one embodiment of the second method for manufacturing a circuit board according to the present invention.

In this second manufacturing method, FIG.
As shown in (a), first, a plating-resistant resist 6 is applied to the surface of the conductive layer 2 so as to obtain a circuit pattern having a predetermined shape. Next, as shown in FIG. 2B, electrolytic plating is performed using the conductive layer 2 as an electrode to form a circuit pattern 12 on the surface of the conductive layer, and then the resist 6 is peeled off as shown in FIG. 2C. The circuit pattern 12 is formed on the surface of the conductor layer 2 as described above.

Next, as shown in FIG. 2D, after the insulating resin layer 1 is formed on the surface of the circuit pattern 12, the conductive layer 2 is formed.
Is removed by etching to form a circuit board having a circuit pattern 12 of a predetermined shape formed on one surface of the insulating resin layer 1.

After a protective metal layer 8 is formed on the circuit pattern 12 as shown in FIG. 2F, ultraviolet laser light is applied to a predetermined position of the insulating resin layer 1 from the side where the protective metal layer 8 is formed. Irradiation forms a hole 4 for conducting the front and back surfaces as shown in FIG. 2 (g). Since the protective metal layer 8 is etched away in a later step, the metal forming the circuit pattern 12 and the metal used for the protective metal layer 8 need to be different so that the circuit pattern 12 is not removed at the same time. Preferably, a more noble metal, a metal having a significantly different oxidation-reduction potential, or a metal which forms a complex with a specific eluent component can be employed. The thickness is adjusted to 0.1 μm or more, preferably 1 μm or more, similarly to the cover resin layer.

Finally, the protective metal layer 8 covering the circuit pattern 12 is removed by etching to obtain the circuit board of the present invention. The hole can be filled with a conductive substance by a known method.

The insulating resin layer 1, conductive layer 2, circuit pattern 12, resist 6 and the like used in each step of the second manufacturing method of the present invention are the same as those described in the first manufacturing method. Any of these can be used, and the same applies to the etching treatment and the peeling method.

[0022]

EXAMPLES Examples of the present invention will be shown below, and will be described more specifically.

Example 1 Copper was sputter-deposited on both sides of a polyimide resin film having a thickness of 25 μm, and further subjected to electroless plating to form a copper layer having a thickness of 3 μm. Next, a photosensitive resist was applied to the surface of the copper layer, and the resist layer was formed into a predetermined circuit pattern by photolithography. After that, wet etching was performed with a ferric chloride solution to form a copper circuit pattern on both surfaces of the polyimide resin film, and then the resist layer was peeled off.

Next, a novolak resin solution was applied to the circuit pattern forming surface side, and a cover resin layer having a thickness of 10 μm was formed by effect. Then, an excimer laser beam was irradiated from the cover resin layer side to form a 25 μmφ hole reaching the circuit pattern on the other surface.

After that, the cover resin layer was removed and the adhering resin decomposed products were also removed at the same time.

Next, the circuit pattern is protected using a plating-resistant resist, only the inner surface and the bottom of the hole are exposed by photolithography, and the hole is filled with gold as a conductive material by electrolytic plating. The plating was continued when the gold was raised to a height of 15 μm from the opening of the hole, and the plating was stopped.

Finally, by stripping the resist,
As shown in FIG. 1 (h), a circuit board having no resin decomposition product attached thereto and having no damage to the circuit pattern was obtained.

Example 2 A photosensitive resist was applied to both sides of a copper foil having a thickness of 18 μm, and formed into a negative pattern by photolithography such that the resist layer on one side had a predetermined circuit pattern. Next, after gold plating was performed on the exposed surface of the copper to form a gold circuit pattern having a thickness of 1 μm, the resist layer was peeled off.

A precursor solution of a polyimide resin is applied to the obtained gold circuit pattern forming surface side, dried and imide-converted to obtain a solution.
A 2 μm thick polyimide resin layer was formed. Thereafter, the copper foil was removed by etching with a ferric chloride solution to obtain a circuit board having a gold circuit pattern on one surface.

Next, nickel was formed as a protective metal layer on the circuit pattern surface to a thickness of 3 μm by electrolytic plating. Then, an excimer laser beam was irradiated from the side where the protective metal layer was formed to form a 15 μmφ hole.

Finally, by removing the protective metal layer with a ferric chloride solution, the adhered resin decomposition product was also removed at the same time, and a circuit board having no damage to the circuit pattern could be obtained.

[0032]

As described above, according to the method for manufacturing a circuit board of the present invention, the resin decomposed product which is generated when the circuit board is irradiated with an ultraviolet laser beam and subjected to fine processing, and the circuit pattern is adhered to the circuit board. It is possible to obtain a circuit board without any damage.

[Brief description of the drawings]

FIGS. 1A to 1H are cross-sectional views of respective steps for explaining one example of a first method for manufacturing a circuit board of the present invention.

FIGS. 2A to 2H are cross-sectional views of respective steps for explaining one example of a second method for manufacturing a circuit board of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating resin layer 2 Conductive layer 3 Cover resin layer 4 Hole 5 Decomposition product 6 Resist 7 Metal substance 8 Protective metal layer 12 Circuit pattern

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-291087 (JP, A) JP-A-3-142091 (JP, A) JP-A-3-190186 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H05K 3/00 B23K 26/00

Claims (3)

(57) [Claims] A step of forming a circuit pattern of a predetermined shape on one or both sides of the insulating resin layer; a step of covering the circuit pattern and laminating a cover resin layer on the insulating resin layer; From the cover resin layer and a predetermined position of the adjacent insulating resin layer is irradiated with high-energy ultraviolet laser light to form a hole for conducting the front and back surfaces, and a step of removing the cover resin layer , Lead to hole
Filling a conductive material to make the surface conductive . Wherein the steps of forming a circuit pattern having a predetermined shape on one side or both sides of the insulating resin layer, forming a protective metal layer on the circuit pattern, a predetermined insulating resin layer from the protective metal layer formation side A method for manufacturing a circuit board, comprising: a step of irradiating a position with a high-energy ultraviolet laser beam to form a hole for conducting between the front and back surfaces; and a step of removing a protective metal layer. 3. The method for manufacturing a circuit board according to claim 2 , further comprising the step of filling the hole with a conductive material to make the front and back surfaces conductive.