Abstract: This article discusses the appearance of "copper powder" in the sulphate copper plating on printed circuit boards, and analyzes the ways of copper powder production.
Keywords: monovalent copper ion, copper powder, chloride ion, phosphorous copper anode.
I. Introduction
The copper powder is formed by the monovalent copper ions in the copper plating solution, which can cause pinhole phenomena such as rough copper plating, burrs, and copper powder falling off. Is the copper coating roughened by monovalent copper ions? After adding 0.03-0.05ml/L of 30% hydrogen peroxide solution to the plating bath, if it is caused by monovalent copper ions, copper powder will be generated after a period of time, indicating that monovalent copper ions are easily generated. At this point, the production of copper powder should be checked.
The second copper powder production route:
1, first check the phosphor bronze anode:
(1) Check whether there is a black film on the surface of the phosphor bronze anode. If there is no black film or black film on the surface of the phosphorus copper anode, it indicates that the phosphorous copper anode has low phosphorus content and cannot control the production of monovalent copper ions and form copper powder. Causes rough copper plating. Phosphorus copper anodes need to be replaced.
(2) Phosphorus copper anodes should not exceed the copper bath level. As the phosphorous copper anode beyond the liquid surface does not have black film protection, when the phosphorus copper anode in the titanium basket gradually falls, when the phosphor bronze anode not protected by the black film falls into the copper plating solution, monovalent copper ions will be quickly generated to form copper. The powder causes rough copper plating; in addition, copper sulfate anodes that are not protected by a black film tend to form cuprous sulphate crystals, and when they fall into the copper plating solution, they quickly produce monovalent copper ions, forming copper powder, which results in rough copper plating. Need to control the amount of phosphorous copper anode added.
(3) The copper or copper crystals cannot adhere to the conductive rod or plate on the electroplating bath. The copper crystal on the conductive rod itself is a monovalent copper ion and falls into the plating solution, rapidly producing monovalent copper ions, forming copper powder and causing copper. Rough plating.
2, check the chloride ion content:
(1) When the chloride ion is too low, the chloride ion cannot fully combine with the monovalent copper ion, and copper cannot sufficiently convert the monovalent copper ion (cuprous chloride) into the divalent copper ion during the formation of the divalent copper ion. (Copper sulphate) forms copper powder and causes rough copper plating; the reduction of chloride ions is mainly caused by large anode area and small cathode area. That is, the small area plate and the small size plate are plated in the large plating bath over a long period of time or in an excessive number of times. A small amount of divalent copper ions is required for the cathode, and a relatively large amount of cuprous chloride at the anode is deposited on the anode, easily falls off, precipitates, or is continuously filtered and removed to cause reduction of chloride ions in the bath.
(2) When the chloride ion is too high, excess cuprous chloride will be formed. This excess cuprous chloride ion will produce a disproportionation reaction and form copper powder, resulting in rough copper plating. The increase in chloride ion content mainly comes from washing water, adding water, and the like.
(3) The central point of chloride ion control is 55 ppm, and the control range is 40-65 ppm. When it is lower than 35 ppm, chlorine ion should be added. When the chloride ion is 75 ppm, it is necessary to prepare for reducing the chloride ion.
Keywords: monovalent copper ion, copper powder, chloride ion, phosphorous copper anode.
I. Introduction
The copper powder is formed by the monovalent copper ions in the copper plating solution, which can cause pinhole phenomena such as rough copper plating, burrs, and copper powder falling off. Is the copper coating roughened by monovalent copper ions? After adding 0.03-0.05ml/L of 30% hydrogen peroxide solution to the plating bath, if it is caused by monovalent copper ions, copper powder will be generated after a period of time, indicating that monovalent copper ions are easily generated. At this point, the production of copper powder should be checked.
The second copper powder production route:
1, first check the phosphor bronze anode:
(1) Check whether there is a black film on the surface of the phosphor bronze anode. If there is no black film or black film on the surface of the phosphorus copper anode, it indicates that the phosphorous copper anode has low phosphorus content and cannot control the production of monovalent copper ions and form copper powder. Causes rough copper plating. Phosphorus copper anodes need to be replaced.
(2) Phosphorus copper anodes should not exceed the copper bath level. As the phosphorous copper anode beyond the liquid surface does not have black film protection, when the phosphorus copper anode in the titanium basket gradually falls, when the phosphor bronze anode not protected by the black film falls into the copper plating solution, monovalent copper ions will be quickly generated to form copper. The powder causes rough copper plating; in addition, copper sulfate anodes that are not protected by a black film tend to form cuprous sulphate crystals, and when they fall into the copper plating solution, they quickly produce monovalent copper ions, forming copper powder, which results in rough copper plating. Need to control the amount of phosphorous copper anode added.
(3) The copper or copper crystals cannot adhere to the conductive rod or plate on the electroplating bath. The copper crystal on the conductive rod itself is a monovalent copper ion and falls into the plating solution, rapidly producing monovalent copper ions, forming copper powder and causing copper. Rough plating.
2, check the chloride ion content:
(1) When the chloride ion is too low, the chloride ion cannot fully combine with the monovalent copper ion, and copper cannot sufficiently convert the monovalent copper ion (cuprous chloride) into the divalent copper ion during the formation of the divalent copper ion. (Copper sulphate) forms copper powder and causes rough copper plating; the reduction of chloride ions is mainly caused by large anode area and small cathode area. That is, the small area plate and the small size plate are plated in the large plating bath over a long period of time or in an excessive number of times. A small amount of divalent copper ions is required for the cathode, and a relatively large amount of cuprous chloride at the anode is deposited on the anode, easily falls off, precipitates, or is continuously filtered and removed to cause reduction of chloride ions in the bath.
(2) When the chloride ion is too high, excess cuprous chloride will be formed. This excess cuprous chloride ion will produce a disproportionation reaction and form copper powder, resulting in rough copper plating. The increase in chloride ion content mainly comes from washing water, adding water, and the like.
(3) The central point of chloride ion control is 55 ppm, and the control range is 40-65 ppm. When it is lower than 35 ppm, chlorine ion should be added. When the chloride ion is 75 ppm, it is necessary to prepare for reducing the chloride ion.