JP2760093B2 - Circuit board manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a circuit board in which terminals of a circuit pattern formed on an insulating base material are short-circuited by a jumper made of a conductive paste. Things.

[Related Art] Conventionally, only a portion of an insulating base material corresponding to each terminal portion is heated and evaporated from a side opposite to a surface of the insulating base material on which a circuit pattern is formed, and a conductive metal of each terminal portion is exposed. As a means for forming, a CO ₂ laser and a YAG laser have been proposed.

[Problems to be Solved by the Invention] However, a YAG laser has an absorptivity of almost zero to a transparent polyester film used as an insulating base material of a flexible substrate during processing, and a conductive material (copper) for forming a circuit pattern. The processing efficiency is poor to the extent that the film is processed by the heat generated by the laser slightly absorbed by the film. Furthermore, since the polyester film is evaporated by heat to process the concave portion, there is a problem that the polyester film cannot be completely removed from the surface of the conductive material to be exposed. Furthermore, a raised portion is formed around the concave portion due to thermal deformation, and there is a problem in printing the conductive paste or in filling the concave portion with the paste.

On the other hand, in the CO ₂ laser, the laser absorptivity to the polyester film is higher than 50% and the processing efficiency is high, but the thin film is easily formed on the surface of the conductive material due to the melting of the polyester film due to thermal processing. It was impossible to completely remove the polyester film as an insulating material with good reproducibility.

The present invention has been made in order to solve the above-described problems, and a polymer insulating material such as polyester forming an insulating base material is completely formed so that the surface of a conductive material forming a circuit pattern is exposed. It is an object of the present invention to provide a method of manufacturing a circuit board that can be removed to form a concave portion accurately.

[Means for Solving the Problems] To achieve this object, the present invention provides a method for manufacturing a circuit board, wherein a polymer insulating material is used as an insulating base material,
An excimer laser with a wavelength λ of 250 nm or less for generating light in the ultraviolet region is irradiated on the insulating base material corresponding to each terminal from the side opposite to the surface of the insulating base material on which the circuit pattern is formed, and is insulated. By removing the base material by an ablation action, a concave portion where the conductive metal of each terminal portion is exposed is formed, and the conductive paste is filled in each concave portion, and the jumper is applied by applying between the concave portions. We take the method of forming.

[Operation] The present invention having the above-described configuration uses a laser having an extremely high energy level belonging to the ultraviolet region to break molecular bonds forming a polymer, and then scatters the broken molecules. Since the concave portion is formed using the ablation phenomenon, the insulating material on the conductive surface, which is a circuit pattern material, is reliably removed to completely expose the surface, and the concave portion is also processed into an appropriate shape.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

First, an example of a circuit board obtained by the manufacturing method of the present invention will be described with reference to FIGS.

The insulating base 1 is made of a polyester film, and circuit patterns 2 and 3 made of a conductive material such as copper are formed on the polyester film by a method such as etching. This circuit pattern 2,3
Is an electrically different circuit pattern, a terminal portion 4 is formed at the tip of the circuit pattern 3, and an ablation phenomenon occurs when an excimer laser, which will be described later, is irradiated on the insulating base 1 below a central portion of the terminal portion 4. Scattered and removed by the recess 5
The conductive material on the lower surface of the terminal portion 4 is exposed on the bottom surface of the concave portion 5 to form a conductive surface 4a. A conductive paste is filled into the conductive surface 4a to form a jumper 6, and the terminal portion 4 is electrically connected. Is electrically conductive.

Next, with reference to FIG. 5, an outline of a laser generator used in the manufacturing method of the present invention will be described.

The laser 12 output from the excimer laser oscillator 11 is
Only a good laser at the center is extracted through the aperture 13. Next, the good laser 12 is
As a result, the light is deflected vertically, enters the processing lens 15, and is condensed on one point of the insulating base material 1, which is the portion to be processed. Also, during processing, an inert gas 16 such as argon (Ar) is supplied from the side in order to skip evaporated molecules.

Next, a method of manufacturing the circuit board shown in FIGS. 3 and 4 by the laser generator will be described with reference to FIGS.

FIG. 6 shows a circuit board before laser processing.
Have circuit patterns 2 and 3 formed on the surface thereof. With respect to the side surface of the insulating base 1 opposite to the terminal portion 4 of the circuit pattern 3,
When the laser 12 is irradiated from the laser generator, the concave portion 5 is formed in the polyester film (100 μm thick) which forms the insulating base 1 below the terminal portion 4 as shown in FIG.
The diameter of the recess 5 is usually about 1 mm. By this processing, the conductive metal forming the terminal portion 4 is exposed, and the conductive surface 4a is formed.

Each of the recesses 5 is filled with the conductive paste, and the conductive paste is applied between the recesses 5 on the surface opposite to the surface on which the circuit turn terminal portion 4 is formed, so that the jumper is formed. 6 are formed, and the circuit board shown in FIGS. 3 and 4 is manufactured. As the conductive paste, a paste in which a conductive metal such as silver powder is mixed as a conductive filler in a binder, a solvent, or the like is used.

Here, when the relationship between the binding energy of the polyester, which is a component of the insulating base material 1, the wavelength of the excimer laser, and the type of laser, was examined, the following was found.

 The chemical formula of the polyester is represented as follows:

The bond having the highest energy in the above bond is a double bond of carbon and oxygen (C = 0), which is 173 Kcal / mo10 ゜ K.

FIG. 2 shows the relationship between the wavelength λ of the excimer laser and the binding energy. As is clear from FIG. 2, the highest binding energy of polyester is 173Kcal / mo10 ゜ K.
To break the double bond (C = 0)
It is necessary to work with F ₂ excimer laser or short-wavelength 7 nm, when the laser 12, since it is a somewhat heated excitation, in fact is the wavelength λ also processing possible with KrF excimer laser of 249 nm. However, with a YAG laser having a wavelength of λ = 1060 nm or a CO ₂ laser having a wavelength of λ = 1060 nm, it is impossible to cut off the binding energy of the above molecules, resulting in a problem of thermal processing.

FIG. 1 shows the relationship between the type of excimer laser, its wavelength λ, and the amount of removal of the polyester film.

As is clear from FIG. 1, the energy density is 1J
polyester film 100 in each excimer laser at / cm ²
The removal amount by ablation of μm was measured assuming that the number of pulse shots was 100 pulses. As a result, ArF and KyF having a wavelength λ of 250 nm or less were completely 100 μm, but the wavelength λ was 3 μm.
It was found that the bonding efficiency of molecules was not sufficiently cut due to the low laser energy of XeCl of 08 nm, and the removal efficiency was poor.

As described above, the insulating base material 1 is formed by excimer laser processing.
The degree of exposure of the conductive surface of the terminal portion 4 exposed on the bottom surface of the concave portion 5 formed as described above was as follows.

From an SEM reference photograph in which the polyester film was processed by excimer laser, it was found that the conductive surface 4a of the terminal portion 4 was damaged by the laser 12, and it can be said that the degree of exposure was excellent. The excimer laser used had a wavelength λ of 249 nm.
An rF excimer laser has an energy density of 1 J / cm ² and a pulse shot count of 180 pulses. The diameter of the recess 5 is approximately 1
mm.

The conductive surface 4a of the terminal portion 4 is completely formed in the concave portion 5 of the reference photograph
Was exposed on the surface and further confirmed by EPMA analysis. FIG. 8 shows the results of analysis of two end positions about 0.1 mm inside the circumference of the recess 5 and the conductive surface 4a at the center. At each point, the peak of the X-ray intensity of the CuKr line is present, and the presence of copper is clearly seen.

FIG. 9 shows an analysis of the enzyme as a component of the polyester at the three points in the same manner as in FIG. 8 described above. However, since no peak of the X-ray intensity was present, the enzyme was not present, and therefore, the residual polyester was almost zero. It can be said that.

Based on the above measurement results, the polyester film forming the insulating base material 1 can be completely removed by irradiation with an excimer laser having a wavelength λ of about 250 nm or less. The electrical conduction was measured and found to be complete.

The number of pulse shots at the time of excimer laser irradiation described above is desirably set as the energy per pulse is reduced as the number increases, so that thermal processing is less likely to occur. At least 100 pulses or more are required.

[Effects of the Invention] As is clear from the above description, according to the present invention, by using an excimer laser having a wavelength λ of approximately 250 nm or less, the insulating base material of a circuit board made of a polymer insulating material is used. It is possible to form an appropriately shaped concave portion in which the conductive surface of the terminal portion is completely exposed by completely removing the terminal portion, and there is an effect that electrical conduction between the terminal portions can be ensured.

[Brief description of the drawings]

FIG. 1 shows the wavelength of the excimer laser used in the present invention,
2 is a graph showing the relationship between the wavelength of the excimer laser and the binding energy, and FIG. 3 is a plan view showing an example of a circuit board manufactured by the manufacturing method of the present invention. , FIG. 4 is AA of FIG.
FIG. 5 is a schematic front view showing an excimer laser processing apparatus, FIG. 6 is a cross-sectional view showing an insulating base material before processing, FIG.
FIG. 8 is a cross-sectional view having a concave portion obtained by processing a polyester film with an excimer laser. FIG. 8 is a graph showing the result of EPMA analysis on whether or not a conductive material (copper) is exposed in the concave portion.
The figure is a graph showing the results of oxygen analysis by EPMA to confirm whether polyester as an insulating material remains in the concave portions. DESCRIPTION OF SYMBOLS 1 ... Insulating base material, 2,3 ... Circuit pattern, 4 ... Terminal part, 4a ... Conductive surface, 5 ... Concave part, 6 ... Jumper, 11 ...
... excimer laser oscillator, 12 ... laser.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-120096 (JP, A) WO 89/1842 (WO, A1) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05K 3 / 40,3 / 00

Claims (1)

(57) [Claims] 1. A predetermined circuit pattern made of a conductive metal formed on one surface of an insulating substrate, and at least one pair provided on the circuit pattern and short-circuited to each other with a part of the circuit pattern interposed therebetween. And a jumper coated with a conductive paste and short-circuiting between the terminal portions, wherein the circuit pattern is formed by using a polymer insulating material as the insulating base material. Above the insulating substrate of the part corresponding to each terminal part from the opposite side of the surface of the insulating substrate that was irradiated with an excimer laser with a wavelength λ of 250 nm or less that generates light in the ultraviolet region, ablation of the insulating substrate By removing by action, a concave portion where the conductive metal of each terminal portion is exposed is formed, and a conductive paste is filled in each concave portion, and the conductive paste is applied between the concave portions to thereby form a conductive paste. Method of manufacturing a circuit board, which comprises forming a jumper.