JPS5929159B2 - Manufacturing method of printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses laser beams to process holes during the manufacturing process of printed wiring boards, thereby improving the reliability of connections between electronic components and conductor circuits, reducing insertion errors of electronic components into holes, and The present invention relates to a method for manufacturing a printed wiring board that can easily improve the connection reliability of front and back conductive circuits.

Conventionally, a copper-clad laminate is used, and the unnecessary copper foil is etched to form a conductor circuit, and if necessary, holes are formed either before or after etching, and then through-hole plating is applied. Printed wiring boards using the method are well known, and include single-sided copper-clad printed wiring boards, single-sided copper-clad through-hole printed wiring boards, and double-sided copper-clad through-hole printed wiring boards.

However, in the manufacturing process of these printed wiring boards, hole processing such as punching or drilling is common, and these methods have the following problems.

B. The through-hole obtained by hole machining is made slightly larger than the lead wire of the electronic component, so when inserting the lead wire of the electronic component into the through-hole and performing the soldering process, the electronic component may fall off and the number of man-hours is increased. It has the disadvantage of increasing.

There are many problems, especially when mass production is performed, such as for consumer use, and automatic insertion and soldering of electronic components are performed. In addition, regarding the reliability of the front and back connections of printed wiring boards in which through-holes are formed in double-sided copper-clad laminates and through-hole plating is applied by chemical plating or electroplating, protrusions (burrs) of the copper foil during hole drilling are ) may occur, or even if no protrusions occur, the same copper foil may have different layers. Especially in the case of paper base materials, cracks may occur in the copper foil due to shrinkage in the direction perpendicular to the base material. There was a problem that the wire was easily connected and disconnected.

The present invention solves the above-mentioned conventional problems and provides a method for manufacturing a printed wiring board that is further improved, and has the following objectives: (a) To facilitate the insertion of electronic components; (c) To improve the reliability of soldering connections between electronic components and conductive circuits on printed wiring boards; (ii) To improve the reliability of connections between front and back conductor circuits by through-hole plating. The goal is to measure improvement.

In the present invention, when an insulating substrate having conductive metal foil on one or both sides is irradiated with a laser beam to form a through hole, the diameter of the through hole in the conductive metal foil is smaller than the diameter of the through hole in the insulating substrate. This is an application of that property.

The reason for this is thought to be that the insulating substrate burns and disappears more quickly when irradiated with a laser beam, whereas the melting temperature or combustion temperature of the conductive metal layer is higher and the rate of disappearance is slower. Embodiments of the present invention will be described in detail below based on the drawings.

Example 1 A 1.67!1I1 thick copper-clad paper-phenol laminate was heated to an output of 450 W1 using a Panaraze GM-CL4 (manufactured by Matsushita Giken Co., Ltd., published in the November 1977 issue of "Machine and Tools" magazine). As a result of irradiation for 0.012 seconds with a beam diameter of 4wItφ, the through hole 3 of the insulating substrate 1 was 0.471 mφ as shown in FIG.
was 0.271I11tφ.

Example 2 Using the same laser device on a 1.6wt thick copper-clad paper-phenol laminate, the output was 450W and the beam diameter was 87!
Irradiation was performed for 0.05 seconds at Illφ to form through holes 3 in the insulating substrate 1 with a diameter of 0.871gtφ and through holes 4 in the copper foil 2 with a diameter of 0.4W1φ.

Next, as shown in FIG. 2, after forming a solder mask 5 by screen printing to prevent solder from adhering to unnecessary parts, the lead wire 6 of the electronic component 8 with a diameter of 0.7 mm is connected to the insulating substrate.
As a result of inserting the lead wire 6 into the through hole 3 of the copper foil 2 and further strongly inserting it into the center of the through hole 4 of the copper foil 2, the electronic component 8 was fixed in such a manner that the lead wire 6 broke through the copper foil 2. Next, as shown in FIG. 2, two sides of the copper foil were soldered and fixed with solder 7. By processing the electronic component 8 as described above, the lead wire 6 is held by the copper piece 9, the electronic component 8 does not fall off during soldering work, and the contact area between the copper piece 9 and the solder 7 is reduced. solder connection strength 12-15Kf/3W1φ (conventional 8
~12Kf/3? φ) was obtained.

Example 3 Using a laser beam under the same conditions as in Example 2, the irradiation angle of the laser beam was tilted so that the axes 10 and 30 of the through hole 3 of the insulating substrate 1 were aligned, and the axis 10 of the through hole 3 was When the laser beam is rotated around the center, one end of the through hole 3 of the insulating substrate 1 becomes tapered 9 as shown in FIG.

The through-hole 3 formed in this manner allows the lead wire 6 of the electronic component 8 to be maintained even if the through-hole position shifts due to dimensional changes during the manufacturing process of the printed wiring board when inserting the component, especially when automatically inserting the component. easily inserted into a predetermined through hole 3;
Moreover, since the lead wire 6 pierces the through hole 4 of the copper foil 2 and the lead wire 6 is fixed, it is possible to prevent the electronic component 8 from falling off during the process up to the soldering process.

Example 4 After forming a through hole 3 in an insulating substrate 1 with a laser beam in the same manner as in Example 2, a portion of the copper foil 2 smaller than the diameter of the through hole 3 in the insulating substrate 1 is punched to form a through hole in the insulating substrate 1. By narrowing down to the 3rd side, a printed wiring board as shown in FIG. 4 was obtained.

Electronic components 8 are mounted on the printed wiring board thus formed.
When inserted into the through hole 3 and soldered, the solder also adheres to the surface of the insulating substrate 1 and the copper foil portion 11 drawn into the through hole 3, so that the soldered connection of the electronic component 8 becomes strong.

Example 5 Copper sulfate 10 p/t 1 ethylene diamine thiacetic acid 14 was applied to the inner wall of the through hole of a printed wiring board created in the same manner as in Example 4, in which the copper foil 2 was squeezed toward the inner wall of the through hole 3 of the insulating substrate 1.
t/T, formalin 10CC/11 sodium hydroxide (
...12.7) and deposited copper until the thickness of the plated copper 12 reached 15μ, resulting in single-sided copper-clad through-hole printing as shown in Figure 5. A wiring board is obtained.

Here, when conventionally performing electroless copper plating, an activation treatment is required as a pretreatment for plating to adsorb palladium metal, which is a catalyst for electroless copper plating, but according to the present invention, through-hole 3 Since this is provided using a laser beam, the inner wall of the through hole 3 of the insulating substrate 1 is carbonized and a carbon layer is formed on the surface, so plating is possible without performing an activation process.

In addition, if activation treatment is carried out, the adsorption layer of palladium metal will increase due to the effect of the carbon layer on the surface of the inner wall of the through hole 3, which will enable dense plating and through hole plating with fewer pinholes. When soldering to through-holes, the gas blown out from the insulating base material is shielded, the occurrence rate of blowholes and pinholes is significantly reduced, and the solder connection reliability is improved. Furthermore, when the lead wire 6 of the electronic component 8 is inserted into the through-hole of the printed wiring board obtained in this way and soldering is performed, the contact area between the solder and the copper foil increases, and the lead wire of the electronic component becomes strong. Since it is fixed, the solder connection reliability is further improved than in the fourth embodiment.

Example 6 A double-sided copper-clad paper-epoxy laminate with a thickness of 1.671i11t was produced using the same laser device with an output of 450W and a beam diameter of 0.8mmφ.
The insulating substrate 1 of 0.871gtφ was irradiated for 0.05 seconds at
Through hole 3 and 0.0471I! A through hole 4 of copper foil 2 having a diameter of 1 tφ is provided, and a printed wiring board as shown in FIG. 6 is produced.

Next, the copper foil 2 on both sides is squeezed onto the inner wall of the through hole 3 of the insulating substrate 1 with a punch, copper sulfate 10r/t1 ethylenediamine 4 acetic acid 14f/t1 formalin 5cc/t1 potassium cyanide 0.002y/T, sodium hydroxide. (PHl2.O
Electroless copper plating foil 13 is formed on the front and back copper foils 2 and in the through holes 3 using an electroless copper plating solution consisting of obtain. According to this example, as in Example 5, electroless plating can be applied to the through holes 3 without performing an activation treatment to adsorb palladium metal, which serves as a catalyst for electroless copper plating. In addition, if you dare to perform activation treatment, the amount of adsorption of palladium metal will increase due to the effect of the carbon layer on the surface of the inner wall of the through-hole, allowing dense plating and through-hole plating with fewer pin horns. When performing soldering, the gas blown out from the insulating base material is shielded, reducing the incidence of blowholes and pinholes. Furthermore, the copper through-hole printed wiring board obtained in this manner can be applied to the corners of the through-holes 3 of the insulating substrate 1 even if shrinkage stress is concentrated due to temperature and humidity in the thickness direction of the insulating substrate 1. Since the corner portions of the through holes 3 of the insulating substrate 1 are covered and reinforced with electroless copper foil formed thereon, cracks do not occur in the corner portions and disconnections do not occur. In other words, the printed wiring board has high through-hole connection reliability. As described above, the present invention has great industrial utility value because the object of the present invention can be easily achieved using a laser beam.

[Brief explanation of drawings]

1 to 7 are cross-sectional views for explaining an embodiment of the method for manufacturing a printed wiring board of the present invention. 1... Insulating substrate, 2... Conductive layer, 3.
...Through hole, 4...Through hole, 9...
... Taper 1 12 ... Plated copper, 13 ...
...Metsuki foil.

Claims (1)

[Claims] 1. A method for manufacturing a printed wiring board, characterized in that a through hole is formed in an insulating substrate having a conductive layer on at least one side using a laser beam, and a through hole having a diameter smaller than the diameter of the through hole in the insulating substrate is formed in the conductive layer. .