JPH06190792A - Boring method for printed circuit board - Google Patents

Abstract

PURPOSE:To establish a method for effectively boring micro-holes having a high aspect ratio in a printed circuit board. CONSTITUTION:A drill 2 is provided with a spiral groove 1 and bores a printed circuit board 3, which has an insulative layer of complex composition of resin compound and an insulative aggregate consisting of one or more of inorganic or organic particles and fibers or of an inorganic porous structure, or a printed circuit board 3 consisting of inorganic sintered body. To the rotary connection part 4 of the drill 2, a liquid 5 having at least a viscosity of 0.1c-poise is supplied at a flow speed of at least 5cm/sec, and boring is performed while a swirl 6 is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for punching a printed wiring board, and more particularly to a method for efficiently punching fine holes in a printed wiring board using a drill having a spiral groove.

[0002]

2. Description of the Related Art Conventionally, a printed wiring board having a conductor circuit, for example, a resin composite substrate such as a glass fiber-epoxy resin substrate or a paper-phenol resin substrate is dry-punched using a drill having a spiral groove. . Usually, when drilling with a drill having a spiral groove, chips are discharged from the spiral groove. In the case of a drill with a fine diameter, the spiral groove must be made small in view of mechanical strength. When the aspect ratio is increased, the discharge of the cutting chips is further deteriorated, so that there is a drawback that the drill burns or is broken. On the other hand, drilling using a drill has not been carried out on a substrate having high hardness and difficult to cut such as alumina ceramic or so-called glass ceramic.

On the other hand, the metal member is drilled in water or lubricating oil, but the hole diameter is 1 at the smallest.
A method of digging holes in mm and having a large aspect ratio was divided into several tens to several thousands of times, and the method was dug in stages, which was very inefficient.

[0004]

With the recent progress in high-density mounting of electronic equipment, the diameter of holes has been increasing as circuit wiring has become thinner and the number of holes per board of printed wiring boards has increased. Is becoming finer. Since productivity is emphasized and several substrates are stacked and simultaneously drilled, a drilling process with a large aspect ratio is required.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for efficiently making fine holes having a high aspect ratio in a printed wiring board. .

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the means adopted by the present invention will be described with reference to the reference numerals used in the embodiments. "Drill (2) having spiral groove (1)" According to the above, a printed wiring board (3) having an insulating layer composed of a composite of an insulating aggregate composed of at least one of particles or fibers made of inorganic or organic substances or an inorganic porous structure and a resin composition, or inorganic A method for making a hole in a printed wiring board (3) made of a sintered body, comprising:
A liquid (5) having a viscosity of at least 0.1 centipoise is applied to the rotary tangent portion (4) of the drill (2) at least 5 cm /
The method is to supply holes at a flow rate of 2 seconds to form a swirling flow (6) while making holes. ”

[0007]

According to the invention, it is important to supply the liquid (5) to the rotary tangent (4) of the drill (2) having the spiral groove (1). In the conventional technology, the liquid supply is simply irradiating the entire surface of the drill or completely immersing the material in the liquid, but with this method, the flow of cutting chips discharged along the spiral groove is disturbed, Especially, when the flow rate of the supplied liquid increases, the liquid flow inside the spiral groove is hindered and conversely the discharge of the cutting chips is suppressed. In the present invention, the above-mentioned drawbacks are extremely small, and the cutting chips are quickly discharged.
Further, it is more effective that the place for supplying the liquid (5) is directed to the insertion portion of the drill (2) into the printed wiring board (3). As the liquid (5), water, freon, synthetic oil, castor oil, polyethylene glycol,
A single product or a mixed liquid of several kinds such as glycerin can be used. Further, an additive such as a rust preventive agent may be added. On the contrary, it is not preferable to use a corrosive fluid that destroys the structure of the printed wiring board, such as an acid or alkali solution.

According to the invention, it is important that the viscosity of the liquid (5) is at least 0.1 centipoise. The reason for this is that if it is smaller than 0.1 centipoise, it moves a long distance in a thin spiral groove, especially in the case of drilling with a large aspect ratio, so the viscous resistance of the liquid becomes smaller than the resistance of the spiral groove wall. This is because the swarf easily adheres to the wall of the spiral groove or is easily accumulated, and the outflow of the swarf is obstructed. On the other hand, if the viscosity is too large, the liquid (5) supplied from the gap (8) between the drill (2) and the hole wall surface (7) tends to be hard to reach the drill tip. Therefore, in the present invention, when the viscosity of the liquid (5) is 0.3 to 200 centipoise, a more preferable result is obtained.

According to the invention, it is important that the supply flow rate of the liquid (5) is at least 5 cm / sec. The reason for this is that if it becomes smaller than 5 cm / sec, the cutting chips discharged from the spiral groove will diffuse into the supply liquid (5), and the liquid containing the cutting chips will be supplied to the drill tip. . Faster feed rates give better results,
The higher the viscosity of the liquid, the higher the flow velocity, which is more effective.
For example, when supplying 1 centipoise of water, a flow rate of 20 cm / sec or more is very good, and with 10 centipoise of lubricating oil, 30 cm / sec or more is very effective. On the contrary, it is 10 cm / with a CFC liquid of 0.3 centipoise.
Greater effect in seconds or more.

According to the invention, it is important to supply the liquid (5) to form the swirling flow (6). By forming the swirling flow (6), it is possible to prevent the generation of turbulence and the retention of the liquid, so that it is possible to prevent the cutting chips discharged from the spiral groove from diffusing into the supply liquid. That is, the flow of cutting chips discharged from the spiral groove of the drill (1
0) and the flow of the feed liquid are effective. Therefore, it is important that the swirl flow due to the supply liquid forms a strong flow even in a very small part, and it is optimal that the swirl flow is formed at the contact portion between the drill and the printed wiring board. If the rotation direction is the same, the above effect is further enhanced.

[0011]

EXAMPLE Next, an example of a method for punching a printed wiring board according to the present invention shown in FIG. 1 will be described. The printed wiring board (3) used was a ceramic in which the porous portion of porous cordierite ceramic having a thickness of 1.6 mm and a porosity of 30% was 100% filled with epoxy resin.
It is an epoxy resin composite substrate (commonly called CERACOM substrate). The drill (2) having the spiral groove (1) has an outer diameter of 0.
It is a 3 mm carbide drill. The diameter of the hole (9) formed in the pressure foot is 1.0 mm, and the viscosity is 1 centipoise from the two directions to the tangent part (4) of the drill contour from two directions at a flow rate of 15 cm / sec. Water (3
% Containing rust preventive agent). The supply direction was the direction in which the drill (2) having the spiral groove (1) was inserted into the printed wiring board (3), and at this time, a swirling flow of about 2 mm was formed around the drill. In this situation, drill speed 600
When drilling was performed at 00 rpm and an insertion speed (drill feed speed) of 600 mm / min into the printed circuit board, no drill breakage was observed, drill wear was small, and drilling was possible up to 3000 holes without replacing the drill. At this time, the holes formed in the printed circuit board were good without cracks.

Same as the above embodiment, but the drilling performance is shown when the type of the printed wiring board and the drill are changed, the type of the supply liquid, the viscosity and the speed are changed, and the direction is changed. Summarized in 1.

[0013]

[Table 1]

[0014]

As described in detail above, according to the method for boring a printed wiring board of the present invention, even for a material that is very difficult to process, it is very suitable for boring a through hole having a high aspect ratio. It is an excellent drilling method. According to this method, not only various printed wiring boards but also metal materials can be easily drilled.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a punching process for a printed wiring board according to an example of the present invention.

[Explanation of symbols]

 1 spiral groove 2 drill 3 printed wiring board 4 drill rotation tangent part 5 supply liquid 6 swirl flow 7 hole wall 8 gap between hole and drill 9 liquid supply port 10 chip flow 11 pressure foot

Claims (3)

[Claims] 1. At least one of particles and fibers made of an inorganic or organic substance by a drill having a spiral groove.
A method for making a hole in a printed wiring board having an insulating layer formed by combining an insulating aggregate made of a seed or an inorganic porous structure and a resin composition, or a printed wiring board made of an inorganic sintered body, A method for punching a printed wiring board, comprising supplying a liquid having a viscosity of at least 0.1 centipoise at a flow rate of at least 5 cm / sec to a rotary tangent portion of a drill to form a swirl flow while punching. 2. The method for boring a printed wiring board according to claim 1, wherein the supply liquid is concentrated at an insertion portion of the drill into the printed wiring board. 3. The method for punching a printed wiring board according to claim 1, wherein the swirling flow generated by the supply liquid is the same as the rotating direction of the drill.