Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-02-06
2002-12-31
Lopez, F. Daniel (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S846000, C029S847000
Reexamination Certificate
active
06499217
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to a method of manufacturing a three-dimensional printed wiring board, and more particularly a method of manufacturing a three-dimensional printed wiring board having an insulating layer formed from a thermoplastic resin.
PRIOR ART
As a rigid board in which a conductor circuit is formed on one or both sides of a prepreg formed from glass cloth impregnated with an epoxy resin, a three-dimensional printed wiring board formed with a recess for housing pin and ball grids and LEDs is known. Such three-dimensional printed wiring boards are sometimes called PGA (pin-grid arrays) boards or BGA (ball-grid arrays) boards.
As shown in
FIG. 5
, in order to manufacture a three-dimensional printed wiring board
12
by forming a recess
11
in a rigid board
10
, a male mold
13
of a predetermined shape in the form of a round or polygonal column called a punching mold is pressed against an intended area for mounting parts on the front surface of a rigid board
10
, a female mold
14
called a die mold is pressed against the back of the rigid board
10
, the rigid board is sandwiched between both molds for hot-pressing to form recesses
11
at required places on the rigid board
10
to make the printed wiring board three-dimensional.
Also, as shown in
FIG. 6
, another method is known in which cutting work called countersinking is done on the front surface of a rigid board
15
to form a recess
16
in an intended area for mounting parts to make the printed wiring board three-dimensional.
As a material for an insulating board of a three-dimensional printed wiring board, a thermoplastic saturated polyester resin is known. A manufacturing method in which during a step of crystallizing such a thermoplastic resin, an insulating board is hot-pressed into a predetermined bent or drawn shape is disclosed in Japanese patent publications 6-93536 and 7-101772.
Problems the Invention Tackles
But in manufacturing a three-dimensional wiring board using a thermoplastic saturated polyester resin for the material of an insulating board, there is a problem that the insulating board deforms around a conductor pattern during hot-pressing, and a force (residual stress) that tends to restore the deformed body to the original state acts on the deformed body. In an extreme case, deformation called “waving” is locally caused.
Also, in manufacturing a conventional three-dimensional printed wiring board using a glass epoxy resin, control of the degree of crosslinking of the epoxy resin to the step of hot-press forming is difficult, so that it is impossible to manufacture satisfactory products in reliability and mass-productivity. Also, for a printed wiring board reinforced with glass cloth, its use is limited because of low flexibility.
Also another problem is that if a three-dimensional printed wiring board for mounting of parts for which soldering heat resistance is required or a three-dimensional printed wiring board for mere electric wiring is subjected to bending, a bending stress acts on a conductor of copper or aluminum rather than on an insulating board made from a resin that is low in elasticity, so that the conductor is liable to be cut.
Furthermore, with a conventional polyimide-family board material, heat-fusing a conductor foil reliably at a relatively low temperature is not an easy thing.
An object of this invention is to solve the above-mentioned problems and provide a strain-free three-dimensional printed wiring board by eliminating residual stresses from the wiring board that has been hot-pressed to make it three-dimensional in the manufacture of three-dimensional printed wiring board using a thermoplastic resin that has a good heat resistance.
Also, another object of this invention is to make it possible to reliably heat-fuse a conductor foil to a polyimide resin board at a relatively low temperature, and also to provide a method of manufacturing a three-dimensional printed wiring board in which an intended three-dimensional shape can be accurately formed by hot-pressing at a relatively low temperature, and to provide a three-dimensional printed wiring board that also has soldering heat resistance and chemical resistance.
A still another object of this invention is to provide a three-dimensional printed wiring board in which conductors are less likely to be cut even if bending work is done after a conductor circuit has been formed.
Means to Solve the Problems
In order to solve the above objects, according to this invention, there is provided a method of manufacturing a three-dimensional printed wiring board, the method comprising the steps of providing a filmy insulator comprising a thermoplastic resin composition containing 65-35 wt % of a polyaryl ketone resin having a crystal-melting peak temperature of 260° C. or over, and 35-65 wt % of an amorphous polyetherimide resin, and having a glass transition temperature as measured when the temperature is increased for differential scanning calorie measurement of 150-230° C., superposing a conductor foil on one or both sides of the filmy insulator, heat-fusing the conductor foil so that the thermoplastic resin composition will satisfy the relation between the crystal-melting calorie &Dgr; Hm and the crystallizing calorie &Dgr; Hc as expressed by the following formula (I), etching the conductor foil to form a conductor circuit, and deforming the printed wiring circuit obtained three-dimensionally.
[(&Dgr;
Hm−&Dgr;Hc
)/&Dgr;
Hm
]≦0.5 (I):
If a protective film is provided so as to cover the conductor circuit before deforming such a printed wiring board three-dimensionally, bending stress will not concentrate on the conductor circuit, so that it is possible to manufacture a three-dimensional printed wiring board having a conductor circuit which is less likely to be cut.
In order to impart soldering heat resistance to the filmy insulator, in the above-described method, the printed wiring board formed with a conductor circuit is subjected to heat treatment so that the thermoplastic resin composition will satisfy the relation expressed by the following formula (II):
[(&Dgr;
Hm−&Dgr;Hc
)/&Dgr;
Hm
]≧0.7 (II):
As the heat treatment, hot-press forming may be employed.
As the conductor foil to be laminated on one or both sides of the filmy insulator, a conductor foil having its surface roughened is preferably employed. As the polyaryl ketone resin, a polyetherether ketone resin is preferable.
In the method of manufacturing the three-dimensional printed wiring board of this invention, an insulating layer is formed which comprises a filmy insulator which contains predetermined amounts of a crystalline polyaryl ketone resin and an amorphous polyether imide resin. Due to excellent properties of these resins, the insulating layer has heat-fusability and soldering heat resistance, and also has flexibility, mechanical strength and electrical insulating properties normally required for a printed wiring board.
The thermoplastic resin composition after a conductive foil has been heat-fused satisfies the relation expressed by the formula (I), has a glass transition temperature of 150-230° C., and the crystal-melting calorie &Dgr; Hm and the crystallizing calorie &Dgr; Hc produced by crystallization while the temperature is being increased satisfies the relation expressed by the formula (I). The progression of crystallization of the polyaryl ketone resin due to heating is adjusted within a suitable range.
The conductor foil heat-fused to one or both sides of the filmy insulator is strongly bonded due to the heat-fusability of the thermoplastic resin composition, so that a precision conductor circuit formed by etching the conductor foil is also strongly bonded and less likely to peel off. The use of a conductor foil having its surface roughened is preferable because the bond strength between the conductor circuit and the insulating layer increases.
In order to three-dimensionally deform the printed wiring board formed with a conductor circuit, bending work
Miyake Toshihiro
Nomoto Kaoru
Sanada Kazuya
Takagi Jun
Taniguchi Koichiro
Lopez F. Daniel
McCoy Kimya N.
Mitsubishi Plastics Inc.
Wenderoth , Lind & Ponack, L.L.P.
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