Description And Reasons of Poor Plating During PCB Electroplating:
21. Mold contamination of the plating solution (more common in nickel plating tanks, because the environment of PH4-5 is suitable for mold growth), it can be seen that there are blooming molds embedded in the plating layer. In this case, disinfection and sterilization measures must be taken. In order to avoid mold contamination, attention must be paid to the implementation of the opening procedure of the production line.
22. Moss pollutes water quality. The workpiece is rinsed in water containing moss organisms, and the moss adheres to the workpiece, and it firmly adheres to the workpiece after drying, which affects the quality of the product. We must pay attention to the possibility of moss pollution every spring and establish a sense of prevention. If the moss contaminates the plating tank, the moss will be embedded in the plating.
23. The porosity of the coating is high. The high porosity of the coating affects the appearance of the coating, affects the protective properties of the coating, shortens the storage period, affects the solderability, and the coating is brittle. The cause is mostly dirty plating solution, many metal impurities, and many organic impurities. The method to identify the porosity of the plating layer is to directly identify the characteristics of the plating solution. Hang the polished and degreasing stainless steel sheet into electroplating for about 0.5-1H. If the coating completely encapsulates the stainless steel sheet, and the coating can be scraped off from the edge with a knife, the entire coating can be torn off, and the toughness is good, forming a whole coating. Direct the coating film face up to the sun. If no pores are visible, it proves that the bath characteristics are very good. If a little bit of light transmission (pores) is visible, it proves that the bath characteristics are poor; if the coating cannot be removed from the stainless steel sheet, and the plating layer is lifted up like fish scales, which proves that the bath characteristics are extremely poor and the bath needs to be treated extensively.
24. There are regular differences in the thickness of the coating on the same rack. This is because the projection of the cathode and anode graphics is not accurate (the relative position of the cathode and anode is not suitable), and the distribution of power lines is uneven.
There are regular differences in the thickness of the coating on the same rack. This is because the elastic contact resistance of the hook where each workpiece is located is different. The coating is thick if the contact is good, and vice versa. It is a problem with the quality of the rack. If there are two hangers in the same tank, one of them has a thick coating and the other has a thinner layer. This is because the two hangers have different degrees of aging. The newer hangers have lower contact resistance and thicker coatings, and vice versa. If the projection of the cathode and anode is correct, the aging degree of the two hangers is also the same, but the thickness of the coating is thick on one side and thin on the other side, which changes regularly. This is due to rust or salt frost on the cathode on one side of the ingot, resulting in poor electrical contact. In order to make both sides of the plating tank have good conduction and eliminate the defect of large voltage drop due to unilateral energization, the length of the plating tank is greater than 1 meter, and both ends need to be powered on, and it must be cleaned regularly to maintain good electrical contact.
25. There are black spots on the surface of some workpieces. There may be two reasons for this:
(1) The hanger package is aging and cracked, and the acid-base salt seeping from the cracks is sprayed out by compressed gas and splashed on the workpiece, contaminating the coating.
(2) The surface of the rinsing water is too low, and the workpieces on the upper layer of the rack cannot be rinsed. Workpieces and gears that cannot be rinsed are cross-contaminated by the dripping of the liquid medicine. Therefore, the rinsing liquid level must be higher than the uppermost workpiece of the rack.
(3) Cross contamination of dripping liquid.
(4) There is oil in the gas.
(5) Pollution caused by manual unloading operations.
26. After the workpiece is dried after plating, it changes color (yellowing) or changes color after a short storage time. There are two possible conditions:
(1) The concentration of the neutralization solution is too dilute and the temperature is too low to achieve the effect of film removal.
(2) The coating has rough crystals, which increases the difficulty of rinsing and removing the film.
27. There are tin tumors on the surface of the coating. This is because the anode mud pollutes the plating solution, the PP bag is leaked, and when the anode is dissolved, it is transferred into the plating solution in the form of ions on the one hand, and some is flushed into the plating solution in the form of atoms and groups of atoms, contaminating the plating solution. When the radicals contact the workpiece, they are embedded in the plating layer to form tin nodules.
28. Heibody has different colors. That is, the black plastic package becomes gray-black. This is because the frame stays in the alkaline solution for too long in the pre-treatment or neutralization tank for electroplating, and the black body has been etched by alkali. The components of the black body include epoxy, leveling agent, curing agent, anti-aging agent, white filler, melanin, etc. When the black body is alkali-etched, the filler will be exposed. White + black is a gray (different color) phenomenon.
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