Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-06-15
2003-10-28
Vidovich, Gregory (Department: 3726)
Metal working
Method of mechanical manufacture
Electrical device making
C029S846000, C029S852000, C029S861000
Reexamination Certificate
active
06637102
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART
The present invention relates to a method for fabrication of industrial parts having high-aspect-ratio through-hole sections at high density, and, more specifically, when using a soft material which is deformed by handling after blanking, to a method for fabrication of industrial parts by which many high-aspect-ratio through-hole sections are formed into industrial parts with a predetermined thickness, with a similar high accuracy to that of hole sections drilled in a thin sheet material.
Reduction in cost, weight, and size has been commonly required in all industrial products, especially in industrial products equipped with many electrical circuits. The requirement of a small size for circuits has resulted in remarkable developments in packaging technologies for these circuits. Among these developments, small through-hole sections have been required to be fabricated with good accuracy for wiring boards having electronic components mounted thereon so as to more densely integrate electronic circuits, while considering cooling effects, and to secure high reliability. Moreover, technologies to accurately drill small through-hole sections in industrial parts have been indispensable, for example, through-hole sections smaller than those of wiring boards, have been required to be drilled with very high accuracy for ink ejecting sections of inkjet printers.
Recently, there have been much more densely integrated electronic circuits, and it has been necessary to drill a larger number of small through-hole sections in a predetermined area of material substrates. Then, it has been necessary for the through-hole sections to be smaller and deeper in the hole dimension, in other words, for the diameter to be smaller and the axial length (depth) of the above through-hole sections to be longer. That is, it has been necessary for those aspect ratios to be higher. Therefore, it has been required to form the through-hole sections with high accuracy. Generally, the aspect ratio denotes the ratio of the diameter to the axial length of the through-hole section when the through-hole section is cylindrical, and that of the shortest distance between mutually opposing edges in a surface where the through-hole section is opened when not cylindrical. Here, the shortest distance between the mutually opposing edges of the hole is depicted by S. in FIGS.
5
(
a
) and
5
(
b
). That is, a high-aspect-ratio through-hole section means a long and narrow hole with a long axial length compared with the diameter or the shortest distance of the hole.
Hole-drilling with a blanking die may be listed as one conventional method for drilling a large number of small through-hole sections in such a sheet material. The above drilling is a method for making industrial parts by performing a one time, blanking of a sheet material with a predetermined thickness using a punch and a die. In the above method, there has been a problem of poor accuracy as a thick sheet material is treated as a blanking object from the beginning, requiring a large clearance between the punch and the die. Moreover, a shearing force larger than that of a thin sheet material is applied during blanking, and a large number of holes are required, especially for the die, when the through-hole sections are formed with a high density. Therefore, the strength of the die may not withstand the above large shearing force, deformation may be caused due to shortage of the rigidity, and, furthermore, the problem of damage may also occur.
FIGS.
3
(
a
) and
3
(
b
) show a drilling state of a through-hole section with a blanking die. As shown in FIG.
3
(
a
), cracks
15
are caused generally from each edge
14
of a punch
10
and a die
12
during blanking, when the punch
10
performs blanking of a sheet material
13
put on the die
12
after provision of a clearance
16
as a space between the punch
10
and the die
12
. The cracks
15
are generated in the vicinity of the clearance
16
, and the accuracy of the through-hole section varies within the range of the clearance
16
. Thereby, according to the method for drilling of through-hole sections with the blanking die, the cross section of the through-hole sections of a sheet material after blanking is generally tapered in the blanking direction, as shown in FIG.
3
(
b
).
The clearance
16
for the blanking die is required to be larger for a thicker sheet material, for example, 4-12% of the sheet thickness for thin sheets, and 18-26% of the sheet thickness for thick sheets, according to “BASIC MACHINING (I)”, published by THE NIKKAN KOGYO SHIMBUN LTD. That is, the accuracy of holes is reduced for a thick sheet material, as described above. Therefore, the above methods are not suitable for high-density drilling of high-aspect-ratio, small through-hole sections, as the sizes of the diameters at the exit side in the blanking direction are uneven.
As an improved method for hole drilling with the above blanking die, there has been a method for obtaining industrial parts with a predetermined thickness, by which, after the thin sheet materials undergo blanking, the thin sheet materials are transferred and laminated. In the above method, since the sheet thickness of the material for blanking at one time is thin, resulting in superior accuracy of the hole sections for each sheet of sheet material in each blanking and reduced shearing force caused by the punch and the die, holes may be drilled very densely. However, there are problems of low production efficiency and high cost, as jigs for transferring the sheet materials and space for lamination are required, and there are an increased number of machining steps. Moreover, since guide pins are needed for precise lamination, waste is also caused by drilling holes other than the necessary through-hole sections in the industrial parts. Furthermore, when using a soft material which can be deformed after blanking, and when the industrial parts are laminated to a predetermined thickness, gaps occur between holes after transfer and lamination and the problem of reduced accuracy of the through-hole sections occurs. Therefore, the above method is not suitable for very dense drilling of high-aspect-ratio, small through-hole sections.
As another conventional method, there is a method for hole drilling with a laser beam, not using the blanking die. It is machining with a laser beam, that is, a machining method in which a work material is exposed to the laser beam after the above beam is focussed with a lens. According to the above machining with the laser beam, there is a fundamental problem of poor accuracy in the case of the high-aspect-ratio through-hole sections, as the through-hole sections are tapered in the propagating direction of the laser beam due to the laser beam focussing method.
FIGS.
4
(
a
) and
4
(
b
) show a drilling state of a through-hole section formed by laser beam machining. As shown in FIG.
4
(
a
), in a laser machining apparatus, a parallel beam light
17
passes through a condensing lens
18
and is focussed for machining at position of a focal distance
20
. A greater distance from the focus causes the laser beam width
19
to become broader, that is, the diameter of the machined through-hole section becomes larger. Thereby, in the case of a larger thickness of the sheet material, while the hole at the exit side in the propagating direction of the laser beam is being drilled, a through-hole portion with a larger diameter is drilled at the entrance side in the propagating direction of a laser beam. As a result, a tapered through-hole section will be formed, as shown in FIG.
4
(b).
Moreover, as thermal energy is used for the laser beam machining, a sheet material to be machined is deformed by the effect of heat, and an altered layer is formed. Thereby, another problem of uneven diameters of through-hole sections also occurs. Even in the above problem, a larger thickness of the sheet material causes a lower accuracy of the through-hole sections, as the sheet material with the larger thickness requires a larg
Kitamura Kazumasa
Takeuchi Yukihisa
Tsuji Hiroyuki
Yamaguchi Yoshinori
Burr & Brown
Compton Eric
NGK Insulators Ltd.
Vidovich Gregory
LandOfFree
Process for producing an industrial member having... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing an industrial member having..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing an industrial member having... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3129749