Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2002-12-27
2004-07-20
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S457000, C428S689000, C428S901000, C428S546000, C428S403000, C361S748000, C361S761000, C174S255000, C174S256000, C174S261000, C216S019000, C216S039000, C216S065000, C216S094000
Reexamination Certificate
active
06764747
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a circuit board which is obtained by forming a circuit on a board comprising a resin composition as a resin molded article, a metal conductor being able to be formed thereon with strong adhesion to the surface of the resin molded article under a plating process, and method of producing the same.
A resin package with a circuit has been widely known as the name of MID (Molded Interconnect Device) which is produced by forming a conductor circuit on the surface of a two or three dimensionally forming component which is molded by resin. In a general resin molding process, thermoplastic resins including polysulfone (PS), polyethersulfone (PES), polyetherimide (PEI), liquid crystal polymer (LCP), and engineering plastics are used.
The cost reducing requirement for a semiconductor element package including IC, CCD and LD is getting more strict year by year. Therefore, it is expected to develop a new process for a resin component with a three dimensionally forming circuit to realize a surface mounting, miniaturization by micro-circuits, good performances such as high temperature stability, chemical resistance and adhesive property as well as good manufacturing usability and environment and so on. It is particularly required to micro-fabricate the width of a circuit conductor and a space width between the circuit conductor of the semiconductor package to less than 50 &mgr;m for the reason that the degree of a semiconductor's integration has been remarkably improved.
In Japanese Laid-open Patent Publication No. 7(1995)-116870 there is disclosed a method for processing the substrate surface which includes a roughening process thereof by an ultraviolet laser irradiation along the circuit pattern on the board which is formed by a compound of copper powder and resin. According to this process, it is shown that the adhesion of the metal layer to the substrate is improved by the roughening process under the laser beam irradiation because the copper powder, which is hardly removed by an ultraviolet laser, remains thereon. The procedure devised in this publication is to improve the adhesion of the metal film by CVD (chemical vapor deposition) and so on through roughening the substrate surface under an ultraviolet laser irradiation. If this procedure should be applied to the method of forming a circuit by electroplating or electroless plating, however, plating layers grow on unwanted parts owing to a metal which is exposed over the surface through deflashing, which makes it difficult to obtain a constant quality of circuit board for such reasons as: the electrical stability of the resin board is not necessarily substantial; the electric insulation performance of the board may decrease depending on the kind and composition of the electroless plating catalyst; and a short circuit may easily occur by metal migration, if the circuit board is used under high temperature and humidity.
On the other hand, the applicant of this invention provided in Japanese Laid-open Patent Publication No. 10(1998)-308562 a method characterized by the steps of forming a roughened plane with several depressions with a nearly constant pitch by laser beam sweeping and irradiation on at least part of the surface of the resin molded article in the sweeping direction, then forming a metal film by a plating process over said roughened plane. However, this method has an operational problem in that it takes too much processing time in creating a thick plating layer.
SUMMARY OF THE INVENTION
To address the above-noted challenges, it is an object of the present invention to provide a circuit board wherein a circuit is formed on a molded article using a resin composition which is inexpensive and is capable of forming a micro-circuit in desired thickness without difficulty, and method of producing the same.
The present invention provides a circuit board comprising a resin composition molded article which is provided with a metal powder coated with an insulation film (which is removable by a chemical solution) and a resin (which is workable by a laser beam), wherein the resin composition molded article is engraved along a circuit pattern by laser beam irradiation, the insulation film over the metal powder being removed by the chemical solution and a plating process then being conducted, and a method of producing the same.
In the circuit board according to this invention, a circuit pattern is formed by engraving the surface of the resin molded article to remove part of the resin under laser beam irradiation, wherein a metal powder is exposed inside the circuit pattern. Since the surface of the circuit pattern is roughened when it is drawn to be a canal-like form by removing the resin under laser beam irradiation, there creates a good adhesion between this roughened surface and the metal deposited by electroless plating at the origination of metal which is exposed inside the circuit pattern.
The metal powder to be used in this invention, being coated by an insulation film, can not function as an origination for metal deposition in the electroless plating process as long as it is covered by this insulation film.
It is possible, in the circuit board and method of producing the same according to this invention, to remove the insulation film from the metal powder only on the specific part which is engraved by laser beam irradiation. Therefore, a metal conductor can be formed with high selectivity on the circuit pattern which is engraved by laser beam irradiation.
Furthermore, the occurrence of a short circuit between the adjacent metal conductors can be avoided with high accuracy by adjusting the greatest particle size of the metal powder to be used in this invention, so that the particle size has the specific proportional relationship against the minimum width between the circuit conductor of the circuit pattern to be formed.
It is further possible, in the circuit board and method of producing the same according to this invention, to obtain a circuit board with high temperature stability, strong solder crack resistance and excellent chemical resistance because a metal film is formed with a strong adhesion to the resin molded article by filling the roughened groove on the surface of the resin molded article which is formed by a laser beam irradiation with the metal deposition deposited by electroless plating process. It is further possible to obtain a semiconductor device with high temperature stability, solder crack resistance and good chemical resistance by using this circuit board.
It is further possible, according to this invention, to improve the plating speed and plating peel strength by conducting an activation treatment on the surface of the metal powder exposed in the circuit pattern with, for example, palladium and so on.
It is further possible according to this invention to reduce the manufacturing cost of the circuit board by using Cu, Ni, or Cr for the metal powder material, and also to reduce the cost of facility improvement because prior art plating lines can be entirely applied to the line for manufacturing this invention's circuit board.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention provides a circuit board comprising a resin composition molded article which is provided with a metal powder coated with an insulation film (which is removable by a chemical solution) and a resin (which is workable by a laser beam), wherein the resin composition molded article is engraved along a circuit pattern by laser beam irradiation, the insulation film over the metal powder being removed by the chemical solution and a plating process then being conducted, and a method of producing the same.
The kind of metal powder to be included in the resin molded article of this invention can be of any kind as long as it can act as seeds in a plating process, exemplified by nickel, cobalt, iron, chrome, palladium, copper, silver and gold, being a particle of one of them or a compound of more than one of them. Among them, copper, nickel or chrome is cost-wise preferable.
It
Inada Kunihiro
Kawano Yasuyuki
Suzuki Youhei
Urakawa Toshiya
Jones Deborah
Mitsui Chemicals Inc.
Xu Ling
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