Stock material or miscellaneous articles – All metal or with adjacent metals – Foil or filament smaller than 6 mils
Reexamination Certificate
2001-11-07
2003-08-26
Zimmerman, John J. (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Foil or filament smaller than 6 mils
C428S612000, C428S626000, C428S327000, C428S457000, C428S935000, C205S076000, C205S109000, C205S182000, C205S317000
Reexamination Certificate
active
06610418
ABSTRACT:
TECHNICAL FIELD
The present invention relates to electrodeposited copper foil with carrier predominantly employed for producing printed wiring boards, and to a method for producing the electrodeposited copper foil.
BACKGROUND ART
Conventionally, electrodeposited copper foil with carrier has been employed as a material for producing printed wiring boards, which are widely used in the electric and electronic industries. In general, electrodeposited copper foil with carrier is bonded, through hot-pressing, onto an electrically insulating polymer material substrate such as glass-epoxy substrate, phenolic polymer substrate, or polyimide, to thereby form a copper-clad laminate, and the thus-prepared laminate is used for producing printed wiring boards of high density mounting.
In hot-pressing, a copper foil, a prepreg (substrate) which is cured into a B-stage, and mirror plates serving as spacers are laid-up in a multilayered manner, and the copper foil and the prepreg are hot-press-bonded at high temperature and pressure (hereinafter the step may be referred to as “press-forming”). When wrinkles are in turn generated in the copper foil to be pressed, cracks are generated in the wrinkled portions, thereby possibly causing bleeding of resin from a prepreg, or open circuit of a formed electric circuit during an etching step followed in production steps of printed wiring boards. In an electrodeposited copper foil with carrier, the carrier foil prevents generation of wrinkles in the electrodeposited copper foil.
Electrodeposited copper foils with carrier are generally divided into two types; i.e., foils with peelable carriers and foils with etchable carriers. Briefly, the difference between the two types of foils lies in the method for removing the carrier after completion of press-forming. In foil with peelable carrier, the carrier is removed by peeling, whereas in foil with etchable carrier, the carrier is removed by etching. The present invention is directed to electrodeposited copper foil with peelable carrier.
However, the peel strength of conventional foils with peelable carrier after completion of press-forming varies considerably, and a preferable strength of 50-300 gf/cm is commonly required. In some cases, a carrier foil cannot be removed from the copper foil. Thus, conventional foils with peelable carrier have a drawback; i.e., target peel strength is difficult to attain. The drawback prevents the widespread use of the electrodeposited copper foil with carrier employed for general use.
Causes of deviation in peel strength of a carrier foil will next be described. Conventional electrodeposited copper foil with carrier, regardless of whether the carrier is peelable or etchable, has a metallic—e.g., zinc-containing—adhesive interface layer between the carrier foil and the electrodeposited copper foil. The amount of metal components forming the adhesive interface layer determines, with slight dependence on the type of the carrier foil, whether the formed copper foil with carrier has peelable carrier or etchable carrier.
In many cases, such a metallic adhesive interface layer is formed electrochemically; i.e., through electrodeposition by use of a solution containing a predetermined metallic element. However, in electrodeposition, controlling the amount of deposition on a very minute scale is difficult, and reproduction of the deposition is unsatisfactory as compared with other methods for forming the adhesive interface layer. In addition, the boundary line of the required deposition amount determining whether the formed carrier becomes peelable or etchable is difficult to adjust; i.e., small variations in amount of a metallic component contained in the adhesive interface layer determine the type of the carrier. Thus, stable peeling performance may be difficult to attain.
From another point of view, such a carrier foil is removed by peeling after completion of press-forming typically carried out at a temperature as high as 180° C. under high pressure and 1 to 3 hours. Components contained in the carrier foil and copper atoms contained in the electrodeposited copper foil may be mutually diffused through the adhesive interface layer. Such mutual diffusion strengthens the adhesion, thereby failing to attain preferred peel strength.
In order to solve the aforementioned drawbacks, the present inventors have proposed electrodeposited copper foil with carrier in which the adhesive interface layer between the carrier foil layer and the electrodeposited copper foil comprises an organic agent such as CBTA, and a method for producing the electrodeposited copper foil.
The aforementioned electrodeposited copper foil with carrier which the present inventors have proposed completely solves a drawback that the carrier foil cannot be peeled. However, in some cases, the electrodeposited copper foil has another drawback in handling thereof due to excessively easy peeleability; i.e., the carrier foil and the electrodeposited copper foil are separated from each other by peeling during handling of the electrodeposited copper foil with carrier.
Principally, an advantage of electrodeposited copper foil with carrier per se is the state where one surface of the carrier foil were as if bonded in a lamination manner to one surface of an electrodeposited copper layer. In other words, the electrodeposited copper foil with carrier can prevent staining the surface of the electrodeposited copper foil with foreign matter and damaging the electrodeposited copper foil layer by maintaining the bonding state at least immediately before an etching step for forming printed circuits, which step is carried out after production of a copper-clad laminate through hot-pressing the electrodeposited copper foil with carrier and a prepreg (substrate)
Thus, separation of a carrier foil and an electrodeposited copper foil during handling of the electrodeposited copper foil with carrier before hot-press-forming is not acceptable.
SUMMARY OF THE INVENTION
In view of the foregoing, the present inventors have conducted earnest studies, and have attained electrodeposited copper foil with carrier which has an adhesion interface layer comprising an organic agent such that the lower limit of peel strength between the carrier foil and the electrodeposited copper foil is controllable, and a method for producing the electrodeposited copper foil with carrier.
There is provided an electodeposited copper foil with carrier comprising a carrier foil, an adhesive interface layer formed on the carrier foil, and an electrodeposited copper foil layer formed on the adhesive interface layer, wherein the carrier foil is formed of a copper foil and the adhesive interface layer contains an organic agent and metallic particles, the organic agent and the metallic particles being intermingled.
Conventional electrodeposited copper foils with peelable carrier, in some cases, have a problem that a carrier foil cannot be readily peeled from an electrodeposited copper foil. The present inventors have resolved the problem by forming an adhesive interface layer comprising an organic agent on the carrier foil and forming an electrodeposited copper foil on the adhesive interface layer. Thus, unevenness in peel strength at the adhesive interface between the carrier foil and the electrodeposited copper foil has been considerably reduced. In most cases, the adhesive interface layer is formed by immersing a carrier foil in an organic agent, and an inorganic metallic component has not intentionally been incorporated into the adhesive interface layer.
However, when an organic adhesive interface layer is formed through immersion and a copper foil layer is formed on the adhesive interface layer through electrodeposition, a trace amount of the copper component may migrate into an organic agent contained in the adhesive interface layer. Although copper can be detected in the adhesive interface layer of actually produced copper foils with carrier through EPMA analysis, the amount is considerably small and copper cannot be identified as microparticles. In addition, the detected
Dobashi Makoto
Hirasawa Yutaka
Iwakiri Ken-ichiro
Sugimoto Akiko
Yoshioka Junshi
Jenkens & Gilchrist
Mitsui Mining & Smelting Co. Ltd.
Zimmerman John J.
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