JP2003209334A - Drill for drilling process and its processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drilling process method to prevent a crack by finding a drill shape which can control the crack occurring on an insulating resin surface, in a substrate process including an insulating resin layer being hard and brittle on its surface. <P>SOLUTION: A torsion angle of a drill for a drilling process is made 35° or more, a top angle is made 110° to 125°, and a first relief angle is made 15° or more. The process using this drill can reduce the crack occurring in the insulating resin layer of the substrate even if plural substrates are overlaid. The crack on a drill's plunging side, furthermore, can be prevented if a paper phenol resin substrate is used as an upper board. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drilling method and a drill suitable for forming a through hole on a printed circuit board by using a drill.

[0002]

2. Description of the Related Art As a portion of a printed circuit board on which a pattern for electrical connection is formed (hereinafter referred to as a land) becomes smaller, a hole diameter required for drilling a through hole is increased year by year. It has become smaller and now has a diameter of 0.3 mm
The following are required:

In drilling with a drill, a phenomenon (hereinafter referred to as "chip") in which a portion around the processed hole is partially chipped due to an impact or the like when the drill cuts into a printed circuit board. In particular, when a circuit pattern is formed on a conductor layer made of metal of a printed circuit board and holes are drilled after adhering insulating resin layers to both surfaces, the resin usually used as an insulating resin is hard and brittle because heat resistance is important. Moreover, since no reinforcing material such as glass fiber is contained, chipping easily occurs. The situation is shown in FIG. In FIG. 6, 1
Numerals 4 and 4 are insulating resin layers, 2 and 5 are lands, 3 is a base layer made of a core material of a printed circuit board, and 8 is a chipped portion.

When a chipping larger than the land diameter occurs around the machined hole, a metal film is plated as a post-process and the photosensitive film is adhered and exposed to light, and the metal film is etched leaving the photosensitive film at the land. However, since the photosensitive film on the land portion is not adhered due to chipping, the metal film on the land portion is also removed by etching, resulting in a problem.
In particular, this problem has become remarkable in recent years when a small land diameter is required.

As a method of preventing this chipping, it is generally practiced to use an aluminum thin plate with a lubricant as an upper plate and stack it on the substrate, but it is not so effective as shown in FIG. .

FIG. 7 shows a progressing process of drilling. 9 is an aluminum thin plate, 10 is a lubricant, 11
Is a lower burr of an aluminum thin plate formed on the lower side, 12 is a drill, and 13 is a tip portion of a bush used for holding and supporting the substrate during drilling. When drilling is done using a drill, the lower burr on the lower side of the thin metal plate 1
1 is formed. After that, when the drill moves to process another hole, the lower burr 11 is pressed by the bush 13 for pressing the substrate, and the chip 8 in FIG. 6 occurs.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to find a drill shape capable of suppressing chipping which occurs on a hard and brittle insulating resin surface, and to provide a drilling method for preventing chipping.

Another object of the present invention is to provide a method for drilling a hole in which a lower burr is less likely to occur, and an upper plate which does not damage the insulating resin layer when the burr occurs is found and a chipping is prevented.

[0009]

In order to achieve the above object, a hole having a helix angle of 35 ° or more, a tip angle of 110 ° to 125 °, and a clearance angle of 15 ° or more is characterized. It is recommended to use a drill for drilling.

2 and 3 show the definition of drill shape specifications. FIG. 2 is a front view and a side view of the drill. A is the drill diameter, B is the blade length, C is the helix angle, E / D is the groove width ratio, F is the web taper, G is the body clearance, H is the core thickness, and J is J.
Is the tip angle, K is the first clearance angle, L is the second clearance angle, and M is the margin width. FIG. 3 schematically shows the cross-sectional structure of the cutting edge of the drill tip, and shows the relationship among the first clearance angle K, the second clearance angle L, and the margin width M. Also, the rake angle is almost the helix angle C
be equivalent to.

In the conventional general drilling process, a substrate whose both surfaces are covered with copper foil is often used, and it is difficult for chipping to occur. Therefore, the drill has a shape that is more focused on hole position accuracy and reduction of burrs than prevention of chipping. Then, the shape of the drill which can suppress generation | occurrence | production of a chip | tip with respect to the hard and brittle insulating resin layer made into the object of this invention was discovered.

FIG. 4 shows the difference in the cutting load direction due to the difference in the tip angle between the conventional drill and the drill according to the present invention. The conventional drills have a subscript 1 and the drills according to the present invention have a subscript 2. J is the tip angle, F is the load vector, and θ is the angle of the load vector measured from the substrate surface. Indicates. Here, the tip angle J ₁ of the conventional drill is 130 ° to 140 °. The chipping becomes more remarkable as the radial force applied when the drill pierces the insulating resin layer on the substrate surface is larger. Therefore, the tip angle J
_By setting ₂ to 110 ° to 125 °, which is an acute angle from the conventional tip angle J ₁ , θ ₁ <θ ₂ is satisfied, and the component of the force in the radial direction is reduced.

On the other hand, when the force in the thrust direction is increased as a result, burrs generated in the metal layer (copper foil) of the land portion formed under the insulating resin layer become large, and the insulating resin layer is peeled off. There is a fear. Therefore, we devised to sharpen the sharpness of the tip cutting edge and suppress the occurrence of burrs.

FIG. 5 shows the direction of the cutting force due to the difference in the tip cutting edges of the conventional drill and the drill according to the present invention. Subscripts 1 are attached to the conventional drill and 2 to the drill according to the present invention, and K is the first
The clearance angle, φ indicates the angle of the cutting force vector measured from the hole bottom surface during cutting. The rake angle is approximately equal to the helix angle C.
Here, the first clearance angle K ₁ of the conventional drill is 10 °.
˜15 °, and the twist angle C ₁ is 30 ° to 40 °. In the present invention, in order to sharpen the cutting edge, the first
The clearance angle K ₂ is set to 15 ° or more, which is larger than K ₁ , and the helix angle C ₂ is set to 35 ° or more, which is a large helix angle, so that the cutting force direction φ ₂ is substantially the same as φ _1. did. It was found that this makes it possible to suppress burrs on the copper foil land portion due to the sharp tip angle J ₂ .

Further, as the upper plate for achieving the above-mentioned other purpose, it is preferable to use a resin laminated plate using a resin material softer than the insulating resin layer material. This is because the resin laminated plate using the soft resin material is less likely to cause the lower burr, and even if it is generated, the resin material is softer than the insulating resin layer material, so that the insulating resin layer is less likely to be damaged.

Particularly, the paper phenolic resin plate is suitable because the occurrence of lower burrs is small, and even if it occurs, the phenolic resin is softer than the insulating resin layer material, so that the insulating resin layer is not easily scratched and the price is low. is there.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The shape of a drill according to the present invention will be described in detail below with reference to FIGS. 2 and 3 used previously. The twist angle C is 35 ° or more, and the tip angle J is 110 ° to 125.
The first clearance angle K is 15 ° or more. In addition, the drill diameter A is 0.05 mm to 0.60 mm in diameter, the number of blades is 2 or more, the groove width ratio E / D is 1 or more, and the second clearance angle L is the first clearance angle K or more (15 ° or more). ), Margin width M is 0.01 m
m or more and the core thickness H is 1/10 or more of the drill diameter A, and the thinning process is not specified. Other blade lengths, drill materials, blade types (straight, undercut, etc.), web taper F, and body clearance G are not specified.

FIG. 1 shows a drill hole drilling method according to the present invention. Reference numerals 1 and 4 are insulating resin layers, 2 and 5 are lands, 3 is a base layer made of a core material of a printed circuit board, 6 is a resin laminated plate used as an upper plate, and 7 is a drill having an acute tip angle according to the present invention. Is. As the resin laminated plate 6, a resin laminated plate using a resin material softer than the insulating resin layer material may be used. In particular, the paper phenolic resin plate is suitable because the occurrence of lower burrs is small, and even if it occurs, the phenolic resin is softer than the insulating resin layer material, so that the insulating resin layer is not easily scratched and the price is low.

[0019]

Examples Table 1 shows a drill according to the present invention and a conventional drill.
Was manufactured in accordance with the specifications described above and a processing test was performed. Here, the production drill is the drill according to the present invention.

[0020]

[Table 1]

Here, HF0 of Sumitomo Electric Tool Net Co., Ltd. was used as the drill material. Further, as the blade tip type, an undercut type in which a blade was attached only to the drill tip portion and the root portion was thin was used, but the length of the blade portion was 0.4 mm.

Table 2 shows the conditions of the processing test.

[Table 2]

Here, since the paper phenolic resin plate needs to have a flat surface, a paper phenolic resin substrate (RCC substrate) having copper foil bonded to one or both sides was used. In a commercially available product, a paper base material appears on the surface, so that the surface has irregularities and cannot be used in the present invention.

<Example 1> As a result of inspecting the holes near the 1200th hole by stacking three substrates, using the "manufacturing drill" according to the present invention and using the "t0.5 mm paper phenol resin plate" as the upper plate, Almost no chipping was observed on any of the three substrates or on both the entry side and the exit side of the drill.

<Embodiment 2> Three substrates are stacked and the "manufacturing drill" according to the present invention is used to obtain "t0.1 aluminum + lubricant".
As a result of inspecting the holes near the 1200th hole using
The chip was generated only on the drill entry side of the uppermost stacked substrate, but almost no other chip was observed.

<Example 3> As a result of inspecting holes near the 1200th hole by stacking three substrates and using "t0.1 aluminum + lubricant" as an upper plate using a "conventional drill", three substrates Chips were found on both the entry and exit sides of all drills.

[0027]

In the processing of a substrate having an insulating resin layer, a conductor layer and a base layer in order from the surface side, the twist angle is 35 ° or more, the tip angle is 110 ° to 125 °, and the most clearance angle is 15 °. By using a drill for drilling, which has the characteristics described above, it is possible to reduce chipping that occurs in the insulating resin layer of the substrate.

In processing a substrate having an insulating resin layer, a conductor layer and a base layer in this order from the surface side, the twist angle is 35 ° or more, the tip angle is 110 ° to 125 °, and the clearance angle is 15 ° or more. By using the drill for drilling having the above characteristics and using the resin laminated plate made of a resin material softer than the insulating resin layer material as the upper plate, it is possible to reduce even cracks occurring in the uppermost insulating resin layer of the substrate.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a processing method of the present invention.

FIG. 2 is a front view and a side view for explaining the definition of drill specifications according to the present invention.

FIG. 3 is a cross-sectional view for explaining the definition of specifications of the tip cutting edge portion of the drill according to the present invention.

FIG. 4 is a view showing a difference in cutting load direction due to a difference in tip angle between a conventional drill and a drill according to the present invention.

FIG. 5 is a diagram showing a difference in cutting force direction due to a difference in cutting edge between a conventional drill and a drill according to the present invention.

FIG. 6 is a diagram showing a result of a processing method using a conventional drill.

FIG. 7 is a diagram illustrating a cause of occurrence of chipping due to a processing method using a conventional drill.

[Explanation of symbols]

1,4 Insulating resin layer 2,5 land 3 Base layer 6 Resin laminated plate upper plate 7 Drill with a sharp tip angle according to the present invention 8 missing parts 9 Aluminum sheet 10 Lubricant 11 Lower burr 12 drills 13 Bush tip

Claims (3)

[Claims] 1. A working drill used for drilling a substrate having an insulating resin layer, a conductor layer and a base layer in this order from the surface side, wherein the helix angle is 35 ° or more and the tip angle is 110 ° to 125 °. A drill for drilling, which has a clearance angle of 15 ° or more. 2. A method for forming a hole in a substrate having an insulating resin layer, a conductor layer and a base layer in this order from the surface side, wherein the twist angle is 35 ° or more and the tip angle is 110 ° to 125 °.
A drilling method characterized by using a drill for drilling having a clearance angle of 15 ° or more. 3. A method of punching a substrate having an insulating resin layer, a conductor layer and a base layer in this order from the surface side, wherein the twist angle is 35 ° or more and the tip angle is 110 ° to 125 °.
A drilling method, characterized by using a drill for drilling having a clearance angle of 15 ° or more and using a resin laminated plate using a resin material softer than an insulating resin layer material as an upper plate.