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Electroless copper plating machine thereof, and multi-layer printed wiring boardRelated Patent Categories: Electricity: Conductors And Insulators, Conduits, Cables Or Conductors, Preformed Panel Circuit Arrangement (e.g., Printed Circuit), With Particular Conductive Connection (e.g., Crossover), FeedthroughElectroless copper plating machine thereof, and multi-layer printed wiring board description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20050252684, Electroless copper plating machine thereof, and multi-layer printed wiring board. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] The present invention relates to an electroless copper plating method of reducing the concentration of byproduct ions and deposition of byproducts in a plating solution, a device thereof, and an application thereof. [0002] The usual electroless copper plating solution contains copper ions, a copper ion complex agent, a copper ion reducing agent, and a pH conditioner, which must be supplied as the plating advances. However, this supply increases anions in pairs with copper ions, oxidant ions of the copper ion reducing agent, and cations of the pH conditioner in the plating solution. [0003] These ions increasing in the plating solution will deteriorate the physical properties of the plated layer, particularly the elongation ratio of the plated layer, reducing the reliability of the plated layer. Further, it reduces the stability of the plating solution and causes abnormal deposition and autolysis. [0004] Conventionally, to avoid such problems and to maintain a constant salt concentration in the plating solution, various plating techniques have been used, such as changing plating solutions at short-time intervals, and continuously adding a new plating liquid to the plating solution in use. However, these approaches require a large quantity of expensive copper plating solution and a lot of labor and money to dispose of liquid wastes. [0005] Japanese Non-examined Patent Publication No. 56-136967 (1981) has disclosed a method of continuously removing such cumulative ions by an electro dialysis. This method requires complicated operations to maintain the optimum pH for dialysis. Further, the ion selecting membrane which allows plating blocking ions only to penetrate the membrane is mechanically weak, difficult to maintain, and too expensive. [0006] Japanese Non-examined Patent Publication No. 7-268638 (1995) has disclosed a plating method characterized by selecting the metallic ion reducing agent and the pH conditioner in the non-electro plating solution so that the oxidant ion of the metallic ion reducing agent and the cation of the pH conditioner may react into an insoluble salt to prevent oxidant ions of said metallic ion reducing agent from increasing in said plating solution. [0007] However, this method is not effective to prevent an increase of anions in pairs with metallic ions. The increase of the anions will deteriorate the plating characteristics. This method also suggests that the use of copper oxide or copper hydroxide in copper plating will suppress characteristic deterioration of the plating solution. In this case, however, the solubility of the copper oxide or copper hydroxide has a great influence. [0008] Solid copper oxide or copper hydroxide is usually added to the plating solution. If the solid is not dissolved completely into the plating solution, the particles left undissolved are plated as the cores. This causes abnormal deposition or autolysis. Further, copper oxide and copper hydroxide are more expensive than copper sulfate as copper ion sources, which is conventionally used for copper plating. That's the reason why copper oxide and copper hydroxide have not been put in practical use. [0009] Japanese Non-examined Patent Publication No. 7-286279 (1995) has disclosed a method of adding barium hydroxide to the non-electro plating solution and removing excessive sulfuric ions as barium sulfate from the plating solution. However, this method using formalin (35% aqueous formaldehyde solution) cannot avoid a consequent increase of oxidant ions of the copper ion reducing agent in the copper plating solution. The oxidant ions of the copper ion reducing agent in this method are formic ions and cannot be removed because barium formate has too great a solubility to be precipitated. [0010] Further, this method does not blow air into the solution while adding barium hydroxide into the plating solution. When alkaline barium hydroxide is added to the plating solution, the pH value of the plating solution becomes higher. In electroless copper plating, the plating solution becomes unstable when its pH goes too high. Consequently, copper may deposit on unwanted places. This abnormal deposition on printed circuits and the like may cause short-circuits, reducing the yield of the products. Deposition on the walls of the plating bath may drastically deteriorate the workability. [0011] The conventional plating equipment is usually designed to directly add copper ions, the copper-ion reducing agent, and the pH conditioner into the plating bath. However, this equipment cannot be free from the floating of solid particles of insoluble salt in the plating solution. The floating solid particles when deposited on wiring boards may cause abnormal deposition on the boards. [0012] If such a solid particle is caught in a through-hole on a printed wiring board, it prevents part of the through-hole from being plated, causing a discontinuity of the wiring (which is termed "through-hole void"). [0013] In continuous electroless copper plating, byproduct ions such as anions in pairs with copper ions and oxidant ions of the copper ion reducing agent increase in the plating solution. This increasing of the byproduct ions prevent the electroless copper plating reaction from forming normal plating layers and reduces the quality of the plated layer. This not only reduces the mechanical properties of the plated layer, but also causes abnormal deposition of metal on unwanted locations. Up to now, there have been disclosed no effective electroless copper plating method of preventing the increase of plating blocking ions or removing the increased plating blocking ions and refreshing the plating solution. SUMMARY OF THE INVENTION [0014] The main purpose of the present invention is to provide a method of removing plating blocking ions such as anions in pairs with copper ions and oxidant ions of the copper ion reducing agent from the electroless copper plating solution and keeping a constant salt concentration in the electroless copper plating solution during plating, a device to realize said method, and applications thereof. [0015] A summary of the present invention is as follows: [0016] [1] An electroless copper plating method using a plating solution containing copper sulfate as copper ion sources, and a copper ion complex agent, a copper ion reducing agent or glyoxylic acid as a copper ion reducing agent, and pH conditioner, wherein said method comprises steps of using the hydroxide of an alkaline earth metal as said pH conditioner to react with sulfuric ions in the electroless copper plating solution into a salt of said alkaline earth metal, removing the precipitate from the plating solution, measuring at least one of the concentration of sulfuric ion in the plating solution (when the copper ion reducing agent is used) and the concentration of oxalic ion in the plating solution (when glyoxylic acid is used) and keeping an optimum sulfuric ion or oxalic ion concentration or preferentially 0.1 mol per liter or less of sulfuric ion and 0.2 mol per liter or less of oxalic ion during plating. [0017] [2] An electroless copper plating method using a plating solution containing copper sulfate as copper ion sources, and copper ion complex agent, a copper ion reducing agent or glyoxylic acid as the copper ion reducing agent, and pH conditioner, wherein said method comprises steps of adding at least one of alkaline earth metal, alkaline earth metal oxide, alkaline earth metal hydroxide, and alkaline earth metal salt (excluding sulfuric salt) to the plating solution to react with sulfuric ions in the electroless copper plating solution into a salt of said alkaline earth metal, removing the precipitate from the plating solution, measuring at least one of the concentration of sulfuric ion in the plating solution (when the copper ion reducing agent is used) and the concentration of oxalic ion in the plating solution (when glyoxylic acid is used) and keeping an optimum sulfuric ion or oxalic ion concentration or preferentially 0.1 mol per liter or less of sulfuric ion and 0.2 mol per liter or less of oxalic ion during plating. [0018] [3] An electroless copper plating machine using a plating solution containing copper sulfate as copper ion sources, and copper ion complex, a copper ion reducing agent or glyoxylic acid as a copper ion reducing agent, and pH conditioner, wherein said device comprises an electroless copper plating bath, a reaction bath which adds at least one of alkaline earth metal, alkaline earth metal hydroxide, alkaline earth metal oxide, and alkaline earth metal salt (excluding sulfuric salt) to said copper plating solution therein to react with and precipitate sulfuric ions or oxalic ion (when glyoxylic acid is used) as an alkaline earth metal salt in said plating solution, a filter unit which separates said metallic salt precipitate, means for measuring at least one of the concentration of sulfuric ion (when the copper ion reducing agent is used) and the concentration of oxalic ion in the plating solution (when glyoxylic acid is used), and means for comparing at least one of said measured concentrations by a preset reference concentration and controlling the quantity of said alkaline earth metal, alkaline earth metal hydroxide, alkaline earth metal oxide, or alkaline earth metal salt (excluding sulfuric salt) to be added. [0019] [4] An electroless copper plating machine using a plating solution containing metallic ions, an agent for reducing said metallic ions, and a pH conditioner, wherein said machine comprises An electroless copper plating bath, a reaction bath adding at least a metal or a compound containing a metal to said plating solution to precipitate ions which suppress generation of said plating metal, and a ultrafiltration unit. [0020] [5] Said filtration unit is preferably a cross-flow type ultrafiltration unit or a filter press type ultrafiltration unit. [0021] [6] A multi-layer wiring board having insulating layers and circuit layers accumulated and cemented alternately wherein the circuit layers are electrically connected by copper-plated through-holes which pass through the insulating layer between said circuit layers or by copper-plated via-holes whose one end is closed and wherein the copper plating of said multi-layer wiring board is made by said electroless copper plating method. [0022] [7] A module having one or more semiconductor elements on said multi-layer wiring board. Continue reading about Electroless copper plating machine thereof, and multi-layer printed wiring board... Full patent description for Electroless copper plating machine thereof, and multi-layer printed wiring board Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Electroless copper plating machine thereof, and multi-layer printed wiring board patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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