Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Patent
1996-07-31
1998-10-27
Lam, Cathy F.
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
428131, 428418, 428458, 428901, 106 123, 106 126, 106 127, 427305, 427437, 4274431, 522100, 523428, 525406, 525407, 525396, H05K 346, H05K 338
Patent
active
058276041
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a multilayer printed circuit board and a method of producing the same.
BACKGROUND ART
Heretofore, a build-up multilayer printed circuit board interposing an interlaminar insulating layer between an outer layer copper pattern and an inner layer copper pattern has been produced, for example, through the following processes 1-9. That is, it is a series of the processes comprising; adhesive for the electroless plating, interlaminar insulating layer, oxidizing agent or the like, treatment (removal of cutting resin dust in the hole through a chemical treatment), electroless copper plating.
On the other hand, in the production process of this type of-the multilayer printed circuit board, the uneven layer is formed on the surface of the inner layer (underlayer) copper pattern, for example, by carrying out copper-nickel-phosphorus plating treatment or the like prior to the above step 2 for improving the adhesion property between the inner layer copper pattern and the interlaminar insulating layer.
In the above production process, however, a part of the surface layer of the inner layer (underlayer) copper pattern is rendered into an exposed state outward from the interlaminar insulating layer by forming the opening for the formation of viahole or the hole for the formation of through-hole. As a result, the exposed surface portion of the inner layer copper pattern is directly exposed to a roughening solution of an adhesive layer for electroless plating such as phosphoric acid, chromic acid or the like, or a soft etching solution such as sodium persulfate or the like at the subsequent step. In this case, there are caused drawbacks that the inner layer copper pattern is discolored around the viahole, and that the surface portion of the inner layer copper pattern is dissolved (so-called hallow phenomenon is caused), and the like. As a result, there is a problem of damaging the appearance of the resulting multilayer printed circuit board.
Furthermore, when the dissolution of the surface portion (uneven layer) is promoted to dissolve the inner layer (underlayer) copper pattern itself, not only the appearance but also the adhesion property between the interlaminar insulating layer and the inner layer copper pattern and plate followed property plate connection are degraded (see microphotographs shown in FIGS. 7(a)-(c)). As a result, there is caused a problem that the reliability of the multilayer printed circuit board is damaged.
As the technique for preventing the dissolution corrosion of the copper pattern, there have hitherto been proposed 1 a technique of forming an electric plated layer of copper, cobalt or nickel and then subjecting to a rust-preventive treatment in JP-A-2-292894, and 2 a rust-preventive technique of forming a roughened surface provided with a thermal deterioration preventive layer with a copper plating bath containing at least one metal selected from zinc, tin and cobalt and then subjecting this surface to a chromate treatment in JP-A-3-283389.
As a technique of forming the uneven layer (roughened layer) on the copper pattern, there has hitherto been proposed 3 a technique wherein a homogeneously roughened electroless copper plated film is formed through an alloy plating of copper, nickel and phosphorus to improve an adhesion property to a prepreg in JP-A-4-116176.
In the technique described in JP-A-2-292894, the chromium oxide is used as a rust-preventive material and is not electrically conductive, so that it is impossible to apply to the via-hole as defined in the invention.
When the technique described in JP-A-3-283389 is applied to an additive type circuit board, chromium is rapidly dissolved in the roughening solution of the adhesive for electroless plating such as hydrochloric acid or sulfuric acid, so that this technique can not be applied to the board.
The technique described in JP-A-4-116176 is not a technique for preventing the dissolution corrosion of the copper pattern.
It is, therefore, an object of the invention to solve the aforementioned
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Kawade Masato
Uno Hiroaki
Ibiden Co. Ltd.
Lam Cathy F.
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