Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2000-03-09
2003-07-01
Lam, Cathy (Department: 1775)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C174S258000, C174S259000, C428S901000
Reexamination Certificate
active
06586081
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to polyimide/metal laminates which are excellent in adhesion and flexible print wiring boards. More particularly, it relates to polyimide/metal laminates and flexible print wiring boards (in particular, flexible print wiring boards having high heat resistance with the use of imide adhesives), multi-layered print wiring boards wherein flexible print wiring boards are laminated, rigid flex wiring boards wherein flexible print wiring boards are laminated on hard print wiring boards, tapes for tape automated bonding (TAB) wherein polyimide/metal laminates are applied to TAB, semiconductor packages such as chips on film (COF) wherein semiconductor devices are packaged directly on print wiring boards and multi chip modules (MCMs), magnetic recording films, solarbatteries, coating films for aerospace materials and filmy resistance elements which are excellent in adhesion under the ordinary conditions and, moreover, can sustain the adhesive strength at a high ratio after exposure to high temperature or high temperature and high humidity and thus can exert favorable functions even in the environment with high temperature and high humidity.
BACKGROUND OF THE INVENTION
With the recent increasing demand for small-sized and high-performance electric apparatuses, flexible print wiring boards are employed more frequently under severer conditions, for example, at high temperature and high humidity. Thus, there have been strongly required polyimide/metal laminates and flexible print wiring boards withstanding the environment with high temperature and high humidity. Flexible print wiring boards are obtained by directly laminating a metal such as copper on a polyimide film by, for example, metallizing or plating, or by laminating a metal layer such as a copper foil on a polyimide film via an adhesive to thereby give a polyimide/metal laminate and then patterning the polyimide/metal laminate by etching the metal part. Therefore, it is also required that polyimide/metal laminates also have adequate mechanical and electrical characteristics so as to withstand the environment with high temperature and high humidity.
Among all, it is particularly strongly required that the adhesion of polyimide films should withstand the environment as described above.
Thus, various attempts have been made to improve the adhesion of polyimide films.
For example, U.S. Pat. No. 4,742,099 (corresponding to Japanese Patent No. 1,948,445) discloses a technique of improving the adhesion of a polyimide film by adding an organotitanium compound thereto. However, this technique suffers from problems such as causing serious coloration of the film and damaging the fragility of the film due to the existence of titanium atoms at a high concentration within the film.
On the other hand, U.S. Pat. No. 5,227,242 (corresponding to JP-A-6-73209) discloses a polyimide having improved surface adhesive strength which is coated with a metal salt of Sn, Cu, Zn, Fe, Co, Mn or Pd. In the invention, in contrast thereto, not any metal salt of Sn, Cu, Zn, Fe, Co, Mn or Pd but titanium is employed as a metal.
Further, U.S. Pat. No. 5,130,192 discloses a method wherein a polyimide film obtained by coating a solidified polyamic acid film with a heat-resistant surface treatment agent followed by imidization is metallized. However, no highly heat-resistant treating agent is employed in the invention.
In these conventional techniques, there arise some problems such that the films are seriously colored and become fragile due to the titanium element which exists at a high concentration within the film.
Moreover, use of the surface treatment agent suffers from additional problems such that a highly heat-stable one should be employed.
The inventors have conducted intensive studies to solve the problems encountering in the conventional art as described above by providing polyimide/metal laminates and flexible print wiring boards, multi-layered print wiring boards wherein flexible print wiring boards are laminated, rigid flex wiring boards wherein flexible print wiring boards are laminated on hard print wiring boards, tapes for tape automated bonding (TAB) wherein polyimide/metal laminates are applied to TAB, semiconductor packages such as chips on film (COF) wherein semiconductor devices are packaged directly on print wiring boards and multi chip modules (MCMs) magnetic recording films, solar batteries, coating films for aerospace materials and filmy resistance elements which are excellent in environmental resistance.
SUMMARY OF THE INVENTION
The polyimide/metal laminate according to the invention is one wherein the polyimide film contains titanium element.
The polyimide/metal laminate according to the invention is one wherein use is made of a polyimide film obtained by casting or applying a polyamic acid onto a substrate; drying the same to give a partly cured or partly dried film made of the polyamic acid or a polyimide; applying an organic solvent solution containing titanium element on the surface of the film, or immersing the film in an organic solvent solution containing titanium element; then converting the polyamide into the polyimide; and drying the film.
It is preferable that use is made of a polyimide film having a titanium atom number concentration on the surface of said polyimide film, determined by X-ray photoelectron spectroscopy, of from 0.01% to 10%.
It is preferable that the partly cured or partly dried polyamic acid or polyimide film as described above has a residual content of volatiles 5 to 100%, preferably 5 to 70% and still preferably 5 to 50%.
It is preferable that the partly cured or partly dried polyamic acid or polyimide film has an imidization rate of 50% or more, preferably 80% or more, more preferably 85% or more and most preferably 90% or more.
It is preferable that the polyimide/metal laminate according to the invention is one wherein use is made of a polyimide film obtained by applying an organic solvent solution containing titanium element onto the surface of the partly cured or partly dried polyamic acid or polyimide film, or immersing the film in an organic solvent solution containing titanium element; removing the excess droplets remaining on the film surface by, for example, using a squeegee roll (generally composed of two rolls held at an interval less than the thickness of film) or spraying an air stream; then converting the polyamide into the polyimide; and drying the film.
It is preferable that the organic solvent solution containing titanium element as described above is a solution of an organotitanium compound, still preferably an organotitanium compound represented by the following formula (1), in an organic solvent:
(R
1
O)
m
—Ti—(OX)
4-m
(1)
wherein m is an integer of 0 to 4, and X represents
(wherein R
1
represents a hydrogen atom or a C
3-18
hydrocarbyl group; R
2
and R
3
represent each a C
3-18
hydrocarbyl group; R
4
represents a C
3-18
hydrocarbyl group or
R
5
and R
6
represent each a C
3-18
hydrocarbyl group; and R
7
represents a C
2-18
hydrocarbyl group), a C
3-18
hydcrocarbyl or carboxylate group or ammonium salts thereof.
The polyimide/metal laminate according to the invention is one wherein the metal is laminated directly on the polyimide film by, for example, the vacuum metallizing method, the sputtering method, or the wet plating method. It is also possible to successively or simultaneously laminate two or more minerals to give an alloy.
The polyimide/metal laminate according to the invention which is obtained by, after laminating the metal directly on the polyimide film, further laminating another metal different from the metal thereon.
The polyimide/metal laminate according to the invention is one which is obtained by laminating the metal directly on the polyimides film by the vacuums metallizing method, the sputtering method or the wet plating method, wherein the polyimide/metal linate has an adhesive strength of 1000 N/m or more at pattern intervals of 3 mm and at a peel angle of 90° and a peel speed of 50 mm/min.
The poly
Akahori Kiyokazu
Nishinaka Masaru
LandOfFree
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