JPH08258032A - Drilling tool for forming viahole and viahole forming method - Google Patents

Abstract

PURPOSE: To accurately form a viahole excellent in shape, not generating the clogging with punching refuse and having a small diameter to a ceramic green sheet by forming the tip part of a punch and/or a die from a super-hard material. CONSTITUTION: A die 2 composed of a super-hard material is fixed to the central part of a die holder 1 composed of a sintered hard alloy such as tungsten carbide or tungsten carbide-cobalt by a solder material or adhesive 3. A punch tip 5 composed of a super-hard material is fixed to a punch 4 composed of a sintered hard alloy by the solder material or adhesive 3. The punch 4 falls to bore a hole in a green sheet. The punched refuse of the green sheet is separated at a position where the punch tip 5 pierces the through-hole of the die 2 and, thereafter, the punch 4 rises to complete the formation of a viahole. By this method, the viahole having a sharp edge can be formed to the green sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drilling tool for forming a via hole in a ceramic green sheet and a method for forming a via hole in a ceramic green sheet using the tool. More specifically, the present invention provides a tool for forming a via hole having a minute hole diameter, which has excellent wear resistance, has a long life, has a good shape of a hole formed in a ceramic green sheet, and is free from clogging by punching scraps. And a method for forming a via hole.

[0002]

2. Description of the Related Art A laminated ceramic substrate for mounting a semiconductor element is usually manufactured by laminating ceramic green sheets on which a conductor pattern and a metallizing layer forming paste are printed and firing them. The ceramic green sheet used here mixes raw materials such as ceramic powder, binder resin, solvent, and thermoplastic, and pulverizes and mixes with a ball mill to form a slurry composition, which is degassed to adjust viscosity. After that, it is made by a method of thinning it by a doctor blade method, stretching it for a long time, and drying it. Since the conductor pattern formed on this green sheet needs to be electrically connected between a plurality of layers, in that case, by forming a via hole in the green sheet and embedding the conductor in the via hole, a predetermined conductor is formed. A method of electrically connecting the patterns is adopted. In recent years, with the high integration of LSIs and the like, the density of circuit patterns has increased, and the need for fine via holes has increased. For example, a conventional via hole has a size of about 0.2 mm at the smallest, but recently, a via hole having a diameter of 0.1 mm or less has been required. To form a via hole,
As shown in FIGS. 4 to 6, a tool including a punch 9 and a die 8 having a through hole 10 for the punch 9 is used (for example, Japanese Patent Laid-Open No. 4-52105). Tungsten Carbide (WC), Tungsten Carbide-Cobalt (WC-Co) for die and punch of
Cemented carbide or cermet is used. When making a hole, the green sheet 6 is placed on the die 8 and the punch 9 is lowered to form the via hole 7 in the green sheet 6. Further, the punch 9 is lowered to penetrate through the through hole 10 provided in the die 8, and the punching waste 12 generated when the via hole is formed is separated from the tip end portion of the punch 9 so that the punch 9 is placed under the die 8. It is a mechanism to drop.

[0003]

When the diameter of the via hole is up to about 0.2 mm as in the conventional case, the above-mentioned drilling method causes no particular problem. However, when the diameter of the via hole is about 0.1 mm or less, the following problems occur with an increase in the number of holes drilled in the green sheet. (A) The shape of the via hole opening on the back side of the green sheet becomes bad. (B) Debris after punching remains in the via hole, resulting in hole clogging. The problems of (a) and (b) above are related to the punch tip and It was found that it was caused by the wear of the die through hole. That is, it was confirmed that the edge portion at the tip of the punch (A portion shown in FIG. 6) and the edge portion at the die through hole (B portion shown in FIG. 6) were worn out and the punchability was deteriorated. When the punch tip portion and the die through hole are worn, naturally, a via hole having a sharp shape is not formed.
In particular, the shape of the via hole opening on the back surface side of the green sheet becomes poor. Further, the punching dust adheres to the tip of the punch, and the detachability from the tip of the punch deteriorates. Therefore, the punching dust adheres to the inner wall of the via hole when the punch rises, and is left there. In order to solve these problems, it is sufficient to frequently replace the punch and the die, but this replacement work requires a lot of time and is economically unusable. The present invention has been made to solve the above-mentioned problems, and it is possible to accurately process a ceramic green sheet with a small diameter via hole that is excellent in shape and has no clogging of punching waste, and has a long life. It is an object of the present invention to provide a tool which is long and excellent in productivity and economy, and a via hole forming method using the tool.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the inventors of the present invention have realized that the via hole forming tool for a ceramic green sheet is made of an ultra-hard material to improve its shape. It has been found that a via hole without hole clogging can be formed and the tool life can be extended, and the present invention has been completed based on this finding. That is, the present invention is characterized by the following via hole forming tool and via hole forming method. (1) For forming a via hole of a ceramic green sheet comprising a die and a die having a through hole attached to a punch and a die holder. In a hole drilling tool, the tip of the punch and / or the die are made of an ultra-hard material, (2) the hole tool for forming a via hole, (2) the ultra-hard material is polycrystalline sintered diamond, A drilling tool for forming a via hole according to item (1), and (3) a method of forming a via hole in a ceramic green sheet using a punch and a die, wherein the tip of the punch and / or
Alternatively, the present invention provides a via hole forming method, characterized in that the die is a drilling tool made of an ultra-hard material.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings. In the present invention, a punch and / or a punching tool for forming a via hole of a ceramic green sheet are used.
Alternatively, the die is made of a super hard material. As the ultra-hard material, for example, single crystal diamond, polycrystalline sintered diamond (diamond compact), boron nitride sintered body, vapor phase synthetic diamond, vapor phase synthetic boron nitride and the like can be used. Among these, polycrystalline sintered diamond is
Since it has higher hardness than boron nitride and does not have a cleavage plane like single crystal diamond, it is less likely to be chipped on the cleavage plane and has excellent impact resistance, and thus it can be used particularly preferably. FIG. 1 (a) is a plan view of a drilling tool for forming via holes of the present invention, and FIG. 1 (b) is
It is sectional drawing of the AA line of Fig.1 (a). At the center of a die holder 1 made of a cemented carbide such as tungsten carbide or tungsten carbide-cobalt, a die 2 made of a superhard material is provided.
Are fixed by a brazing material or an adhesive 3. A punch tip 5 made of a super hard material is fixed to a punch 4 made of a cemented carbide by a brazing material or an adhesive 3. Usually, the through hole of the die and the tip of the punch are circular, and the diameter of the through hole of the die is processed to be several microns to several tens of microns larger than the diameter of the punch tip. During punching, the center of the through hole of the die and the center of the punch tip are adjusted so as to be completely aligned with each other. FIG. 2 is an explanatory diagram of a via hole forming method using the via hole forming drilling tool of the present invention. As shown in FIG. 2A, the ceramic green sheet 6 is placed on the die and die holder. Then, as shown in FIG. 2 (b), the punch descends to make holes in the green sheet. After the punching waste 12 of the green sheet is released at a position where the tip of the punch penetrates the through hole of the die, the punch rises as shown in FIG. 2 (c), the via hole formation is completed, and the green sheet has a sharp edge. A via hole is formed. FIG. 3 is an explanatory view of a via hole forming tool of the present invention and a via hole forming method using the tool. 3 (a) is a partially enlarged view of FIG. 1 (b). The die 2 is fixed to the die holder 1 with the brazing material or the adhesive 3, and the punch 4 is fixed with the brazing material or the adhesive 3. The punch tip 5 is shown. FIG. 3B is a sectional view of the green sheet 6 in which holes are punched by the punch tip and the die, and a true cylindrical via hole 7 having a sharp edge is formed.
There is no particular limitation on the method of processing the tip of the punch made of an ultra-hard material used in the drilling tool for forming a via hole of the present invention, and an ordinary method of processing an ultra-hard material can be used. For example, using a columnar ultra-hard material, medium finish of outer diameter by centerless polishing, rough finish of length by cutting, finish of outer diameter by centerless polishing, length edge surface finishing by end face grinding polishing and cutting edge finishing by centerless polishing By performing polishing, a cylindrical punch tip can be manufactured. Further, there is no particular limitation on the method for processing a die made of an ultra-hard material used in the drilling tool for forming a via hole of the present invention, and a usual method for processing an ultra-hard material can be used. For example, a cylinder manufactured by the same method as the above punch tip is subjected to die-sinking electrical discharge machining using a highly accurate electrode, punching holes, finishing the cutting edge, and polishing the die surface to form a die. Can be manufactured. The die can be fixed to a die holder made of cemented carbide by brazing with a silver solder or the like, or by adhering with a heat resistant adhesive or the like.

FIG. 4 (a) is a plan view of a conventional drilling tool for forming via holes, and FIG. 4 (b) is a sectional view taken along the line A--A of FIG. 4 (a).
It is sectional drawing of a line. The die of the conventional drilling tool for forming a via hole does not have a die portion made of a super hard material, and the portion including the die of the present invention and the die holder constitutes the die 8 as a whole, and is made of a cemented carbide, for example, tungsten carbide. ,
It is formed of tungsten carbide-cobalt or the like. Further, the conventional punch 9 does not have a punch tip made of a super hard material unlike the punching tool of the present invention, and is entirely formed of a super hard alloy such as tungsten carbide or tungsten carbide-cobalt. FIG. 5: is explanatory drawing of the via-hole formation process using the conventional drilling tool for via-hole formation. As shown in FIG. 5 (a), the ceramic green sheet 6 is placed on the die, and as shown in FIG. 5 (b), the punch is lowered to punch holes in the green sheet, and then, as shown in FIG. 5 (c). As shown in (4), the punch rises to complete the via hole forming step, and the via hole 7 is formed in the green sheet. However, the conventional drilling tool for forming a via hole does not have a punch tip and a die made of an ultra-hard material, so the cutting edge of the punch and die rapidly wears and sharp edges as the green sheet drilling is continued. lose. FIG. 6 is an explanatory diagram of a worn conventional drilling tool for forming a via hole and a via hole forming process using the tool. FIG. 6 (a) is a partially enlarged view of FIG. 4 (b) and schematically shows a state in which the cutting edges of both the die 8 and the punch 9 are worn. FIG. 6B is a cross-sectional view schematically showing a green sheet in which holes have been punched by a worn punch and die, and the corner 11 of the via hole opening on the back surface side of the green sheet from which the tip of the punch comes out is cut off. The shape of the opening is defective. Also, FIG. 6 (c)
When a hole as shown in FIG. 6 (b) is punched, since the releasability of punching scraps of the green sheet from the punch tip portion deteriorates, the punching scrap 12 is left in the via hole 7 when the punch is pulled out, and the hole clogging occurs. Shows a state in which is generated. Before the shape of the via hole formed in the green sheet deteriorates and before the hole is clogged, the punch and die must be replaced and the drilling tool must be readjusted. Had to be replaced and readjusted about every 200,000 to 300,000 shots. The replacement of the punch and the die and the readjustment of the drilling tool are time-consuming operations, and the cost of the punch and the die is high, so that it is not possible to economically and efficiently form the fine via hole of the ceramic green sheet. The drilling tool for forming a via hole of the present invention,
It is possible to form a via hole having a sharp edge for a long period of time, which has a life of 20 times or more that of a conventional drilling tool for forming a via hole. Further, according to the drilling tool for forming a via hole and the via hole forming method of the present invention, the number of times of exchanging and re-adjusting the punch and the die can be significantly reduced, so that it is economical to form a fine via hole in the green sheet with high accuracy. Can be done efficiently and efficiently.

[0007]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Example 1 0.12 mm in diameter and 0.1 in height from polycrystalline sintered diamond
A 0 mm columnar punch tip was manufactured and silver brazed to a tungsten carbide punch having a diameter of 0.12 mm. Also,
It has a cylindrical shape with a diameter of 2.0 mm and a height of 0.30 mm, and has a diameter of 0.3 at the center.
A die having a hole of 14 mm was manufactured and silver brazed to a die holder made of tungsten carbide. As described above, the diameter of the through hole of the die was 20 μm larger than the diameter of the punch tip. A punch and a die were combined to form a via hole forming tool. A binder and a solvent were blended with a ceramic powder containing alumina as a main raw material, and the mixture was mixed with a ball mill to prepare a green sheet having a thickness of 0.3 mm by a doctor blade. When a via hole was formed in this green sheet using the above-mentioned drilling tool, 50
Even after the 10,000 shots, a normal via hole having a sharp edge was formed. Comparative Example 1 A punch and a die made of only tungsten carbide and having the same dimensions as in Example 1 were manufactured without using polycrystalline sintered diamond, and both were combined to form a via hole forming drilling tool. Using this drilling tool, Example 1
When a via hole was formed in the same green sheet as above, the shape of the via hole opened in the green sheet became defective after 250,000 shots, and at the same time, hole clogging occurred and it was necessary to replace the punch and die. When the punches and dies after the replacement were observed, wear was recognized on all the cutting edges. Although the punch tip and the die are made of a super-hard material in the above embodiment, the object of the present invention can be sufficiently achieved even if either of them is used. Therefore, an ultra-hard material may be used only for the punch tip or die.

[0008]

The drilling tool for forming a via hole of the present invention has a punch tip and a die of an ultra-hard material, and when used for fine hole processing of a via hole of a ceramic substrate, without causing burrs around the hole for a long time, It is possible to obtain a ceramic substrate having excellent flatness. In addition, since the number of times of exchanging the tip of the punch and the die is reduced, it is possible to reduce the cost for forming via holes in the ceramic substrate, including jig and tool costs and setup.

[Brief description of drawings]

FIG. 1 is a plan view and a cross-sectional view of a via-hole forming drilling tool of the present invention.

FIG. 2 is an explanatory view of a via hole forming method using the via hole forming drilling tool of the present invention.

FIG. 3 is an explanatory view of a via hole forming tool of the present invention and a via hole forming method using the tool.

FIG. 4 is a plan view and a sectional view of a conventional drilling tool for forming via holes.

FIG. 5 is an explanatory diagram of a via hole forming step using a conventional drilling tool for forming a via hole.

FIG. 6 is an explanatory view of a worn conventional drilling tool for forming via holes and a via hole forming process using the tool.

[Explanation of symbols]

 1 Die holder 2 Die 3 Brazing material or adhesive 4 Punch 5 Punch tip 6 Green sheet 7 Via hole 8 Die 9 Punch 10 Through hole 11 Chipped corner 12 Punching waste

Front Page Continuation (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location H05K 3/00 H05K 3/00 K 3/46 6921-4E 3/46 Y (72) Inventor Hideaki Inamasu Mie Prefecture 2331 Tianjingawa, Saimyoji, Ueno City Asahi Dai Yamond Industry Co., Ltd., Mie No. 2 Factory (72) Inventor Masanori Nakanomori 13 Tanabe-cho, Tsubaki-gun, Kyoto Pref. Kitamachida 13 Nichidai Co., Ltd. Kazumi Yamaguchi Prefecture Omine-cho Omine-cho East branch Iwakura 2701-1 Sumitomo Metal Ceramics Co., Ltd.

Claims (3)

[Claims] 1. A punching tool for forming a via hole of a ceramic green sheet, which comprises a die equipped with a punch and a through hole through which the punch penetrates. In the punching tool for forming a via hole of a ceramic green sheet, the tip of the punch and / or the die are made of a super hard material. A drilling tool for forming a via hole, which is characterized in that 2. The drilling tool for forming a via hole according to claim 1, wherein the ultra-hard material is polycrystalline sintered diamond. 3. A method of forming a via hole in a ceramic green sheet by using a punch and a die, wherein a tip end portion of the punch and / or the die uses a drilling tool made of an ultra-hard material. Forming method.