JPS61149464A - Steel for die for working printed wiring board - Google Patents

Abstract

PURPOSE:To provide a steel for dies having improved suitability to drilling with a drill having a small diameter by incorporating a restricted amount of one or more among Pb, S, Te, Bi and Se into a steel having a specified composition. CONSTITUTION:This steel for dies for working a printed wiring board consists of, by weight, 0.6-1.1% C, 0.1-1.0% Si, 0.7-2.5% Mn, <=0.5% Cu, <=0.5% Ni, 0.3-2.5% Cr, 0.1-2.5% Mo, 0.02-0.60% in total of one or more among Pb, S, Te, Bi and Se, and the balance Fe with impurities. Pb, S, Te, Bi and Se in the composition are effective in improving the suitability to drilling with a drill having a small diameter. The steel has the superior hardenability required for a steel for dies and is hardly deformed by heat treatment.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is suitably used as a material for a mold when a mold is used to process a large number of wiring holes formed in a printed wiring board. This relates to steel for printed wiring board processing dies.

(Prior art) In recent years, wiring connections between components in various electronic devices, etc.
The conventional method of soldering connections using lead wires has been replaced by a method using boards with copper foil printed wiring, and the demand for printed wiring boards has increased significantly.

Conventionally, as such printed wiring boards, paper phenol-based boards have been mainly used for consumer use, and epoxy resin + glass cloth-based boards have tended to be used for industrial use. Among these, the former accounts for more than half of the demand for printed wiring boards because it is advantageous in terms of cost, although its heat resistance and strength are slightly lower. Furthermore, although the cost of the latter is higher than that of the former, it has superior performance such as heat resistance and strength, and demand is increasing at a high rate with the trend toward higher density wiring.

In such a printed wiring board, a large number of wiring holes (about 0.6 to 1.5+sm in diameter) are provided.
Broadly speaking, two types of methods for forming the wiring conductive holes are employed. One of these methods is to drill directly into the printed wiring board to form wiring holes, and although this method is currently the most commonly used, it takes a considerable amount of time to process. At the same time, the amount of drills consumed is large, and the cost is high. Another method is to form wiring holes by punching using a mold. Although a mold is required and the cost tends to be high, the processing efficiency is extremely good, especially in the case of mass production. Since mold costs are relatively reduced, there is a tendency in the future to increasingly adopt a processing method in which wiring holes are formed by punching using a mold.

In the case of punching using such a die, a small-diameter punch and die are used as the cutting die, and the die has a large number of die holes.

Therefore, the mold steel used for this die must not only have the properties required as normal mold steel, but also be particularly good at drilling with a small diameter drill. be done.

By the way, the mold steel conventionally used as this type of die material is JISSK.

SKS, SKD, etc. have been used, but these conventional steels for molds are not particularly good at drilling with a small diameter drill.

(Objective of the Invention) This invention was made in view of the above-mentioned conventional circumstances. It satisfies the following conditions: 1. There is no need to worry about cracking and there is very little risk of uneven heating; 1. Heat treatment deformation is extremely small and high precision can be obtained; 2. excellent toughness and wear resistance. In addition, it is a steel for molds that fully satisfies the requirements of excellent hole-drilling performance with a small-diameter drill, and is especially suitable for wiring conductors for dies used in processing printed wiring boards. The object of the present invention is to provide a mold steel suitable for forming die holes for hole punching.

(Structure of the Invention) The steel for printed wiring board processing molds according to the present invention has a weight percentage of C: 0.6 to 1.1% and Si: 0.1 to 1.0%.
, Mn: 0.7 to 2.5%, Cu: 0.5% or less, Ni
: 0.5% or less.

Cr: 0.3-2.5%, Mo: 0.1-2.5%, and one or more of Pb, S, Te, Bi, and Se in a total of 0.02-0. 60%, the balance being Fe and impurities, and is characterized by excellent drilling workability, particularly with a small diameter drill.

Next, the reason for limiting the composition range (weight %) of the steel for printed wiring board processing molds according to the present invention will be explained.

C (carbon); C is an element effective in increasing the hardness of martensite, forming special carbides through tempering, and providing the hardness and wear resistance necessary for steel for printed wiring board processing molds. In order to obtain such an effect, it was contained in an amount of 0.6% or more. However, if the content is too large, the toughness will decrease, so the content is set at 1.1% or less.

St (Silicon): St is used as a deoxidizing agent and at the same time is an element effective in improving tempering hardness, toughness, and corrosion resistance, so it was contained in an amount of 0.1% or more. However, if it is added in a large amount, the workability, especially the workability of drilling with a small diameter drill, will deteriorate, so it is set at 0.1 to 1.0%.

Mn (manganese): Mn acts as a deoxidizing and desulfurizing agent, improving the cleanliness of steel and at the same time contributing to improving hardenability.In particular, it suppresses the expansion of martensitic transformation during heat treatment and reduces heat treatment deformation. It is an effective element for significantly reducing the amount of carbon, and in order to obtain this effect, it is contained in an amount of 0.7% or more. but,
Addition of a large amount will reduce workability, particularly the workability of drilling with a small-diameter drill, so it was limited to 2.5% or less.

Cu (copper): Since Cu impairs the toughness of steel for printed wiring board processing molds, its upper limit was limited to 0.5% or less.

Since Ni impairs the hole-drilling properties of printed wiring board processing mold steel, especially with a small-diameter drill, its upper limit was limited to 0.5% or less.

Cr (chromium): Cr is an effective element that dissolves in the matrix during hardening to improve hardenability and forms Cr carbide to improve the wear resistance of steel. 0.0 to get the effect.
The content was 3% or more. However, since adding too much will reduce toughness, it is limited to 2.5% or less.

Mo (molybdenum): Mo is an element that is effective in improving wear resistance by forming a solid solution in the matrix during quenching and forming carbides, and at the same time, is effective in increasing resistance to softening during quenching and tempering. In addition to increasing high-temperature tempering hardness, it is an element that also contributes to improving corrosion resistance, and in order to obtain such effects, it is included in an amount of 0.1% or more. However, if it is too large, the toughness and workability, especially the workability of drilling with a small diameter drill, are reduced, so it is limited to 2.5% or less.

Pb (lead), S (sulfur), Te (tellurium).

Bi (bismuth), Se (selenium); Pb, S, Te, Bi, and Se are all elements that are effective in improving the hole-drilling property of the printed wiring board processing mold steel according to the present invention, especially with a small-diameter drill. Therefore, one or more of these were included. In this case, if the total of these is less than 0.02%, the effect of improving the drilling workability with the small-diameter drill described above is small, so it is set to be 0.02% or more. However, if too much is added, the above-mentioned effect of improving the drilling workability will not be large and the toughness will be reduced, so the total amount was limited to 0.60% or less.

(Example) Steel having the chemical composition shown in Table 1 was melted by ladle refining (LF) and vacuum degassing (DH), and then ingot-formed and subjected to one-segment rolling and product rolling.

Next, from the above-mentioned rolled material, a thickness of 16 mm and a width of 350 m was obtained.
m, cut out a mold material with a length of 400 mm, and high-speed fi
Drilling was performed using a small-diameter drill (diameter 0.6 mm) manufactured by SKH Co., Ltd. under the conditions of a rotation speed of 900 rpm, a feed rate of 0, and 0.6 + am/re.

When the total cutting length until the end of the life of the small diameter drill was investigated, the results are shown in Table 2.

As shown in Table 2, the total cutting length of the inventive steels No. 001 to 5 that satisfy the composition range of the invention is that of the comparison steel No.
This value is considerably larger than that of 8 to 9, and it is clear that the hole-drilling property is particularly excellent with a small-diameter drill. In addition, in the case of the steel of the present invention, the chip breakability during drilling was good, and the occurrence of burrs during drilling was small, so stable and good processing efficiency was obtained.

Next, the sample material after the above drilling process was quenched and tempered to have a hardness of HRC58 to 60.

When the heat treatment dimensional change (dimensional change rate) of each sample material after this heat treatment was measured, the results were also shown in Table 2.

As shown in Table 2, the present invention steel N
It is clear that the dimensional change ratios of Nos. 011-5 are no different from those of comparative steel Nos. 006-9 and are in fact superior.

Table 2 [Effects of the Invention] As explained above, the printed wiring board processing mold steel according to the present invention has a carbon content of 0.6 to 1.1% by weight.
, Si: 0.1-1.0%.

Mn: 0.7 to 2.5%, Cu: 0.5% or less, Ni:
0.5% or less, Cr: 0.3 to 2.5%.

Mo: 0.1-2.5%, and pb, s.

Since it is composed of one or more of Te, Bi, and Se in a total of 0.02 to 0.60%, and the balance is Fe and impurities, it has a considerably high hardenability required for mold steel. At the same time, the heat treatment deformation is extremely small, the heat treatment unevenness is small, and the wear resistance is good.In addition, it is extremely easy to drill holes using a small-diameter drill, making it ideal for forming wiring holes on printed wiring boards. A very excellent effect can be obtained in that it is suitable as a steel for forming molds when punching a large quantity and efficiently using a mold.

Claims (2)

[Claims] (1) In weight%, C: 0.6 to 1.1%, Si: 0.1~1.0%, Mn: 0.7~ 2.5%, Cu: 0.5% or less, Ni: 0.5% or less,
Cr: 0.3 to 2.5%, Mo: 0.1 to 2.5%, and one or two of Pb, S, Te, Bi, and Se.
A steel for molds for processing printed wiring boards, characterized in that it is composed of 0.02 to 0.60% in total of 0.02% to 0.60%, the balance being Fe and impurities, and is particularly excellent in drilling workability with a small diameter drill.