Various prevention methods of silver dipping process for PCB

The following five common silver dip defects have found some prevention and improvement methods through the on-site scientific research of Yao water supplier, machine equipment supplier and PCB board, which can show how to solve the difficulties and improve the qualification rate in the work of multi-layer PCB circuit board factory, and are described below:

1. Multi layer circuit board Giavanni copper biting

This problem must be traced back to the copper electroplating process. It is found that if we can show examples of deep hole barrel plating and buried hole barrel plating with the goal of high thickness diameter ratio, if we can show them with more symmetrical distribution, we can reduce this kind of Giavanni copper biting situation. In addition, the stripping and etching process of metal material inhibitors (such as pure tin layer) in the multi-layer circuit board manufacturing process, such as copper, will also cause gaps and deposit electroplating process solution and micro etching solution once there are too many etching processes and side etching conditions.

In fact, the major source of Jafani's problem is the green paint project, in which the side erosion and film relief patterns caused by the green paint condition are most likely to lead to gaps. If the green paint can cause positive foot residue rather than negative side erosion, and the green paint is completely hardened, the lack of such Giavanni copper bite can be removed. For the actual operation of electroplating copper, try to make the electroplating copper in the deep hole more symmetrical in the obvious mixing. At this time, it is also necessary to use the help of ultrasonic wave and intensifier to mix, so as to improve the mass transfer of the bath solution and the spread of copper thickness. For the silver immersion process of PCB, it is necessary to strictly control the micro etching copper biting rate of its front end. Smooth copper surface can also reduce the existence of gaps after green paint. Finally, the silver bath itself should not show too strong copper biting reaction, and the pH value should be neutralized, and the plating speed should not be too fast. It is better to cut the thickness as thin as possible, and the anti fading effect can be done well in the optimized silver junction crystal.

multilayer circuit board

2. Improvement of fading of multilayer circuit board

The way to improve it is to increase the relative density of the coating and reduce its porosity. Sulfur free paper should be used as far as possible for packaging goods, and its sealing should be in many ways to block the carbon dioxide and sulfur in the air, so as to reduce the source of its fading. In addition, the average temperature of the storage management natural environment is not suitable to exceed 30 ℃, and the environmental humidity must be less than 40% RH. It is better to adopt the current policy of "top priority" to prevent problems caused by long-term storage.

3. Improvement of Ionization Environmental Pollution on PCB Surface of Multilayer PCB

If the concentration of ions in the silver bath can be reduced without hindering the coating quality, the ionized ions on the surface will certainly be enough to reduce the drug. During the cleaning after immersion plating, it should also be soaked with purified water for more than one minute before it becomes dry, so as to reduce the ionization of adhesion. In addition, the cleanliness of the finished PCB should also be tested regularly to minimize the residual ionization on the PCB surface and meet the industry standards. All experiments made should be stored in their records so that they can be prepared.

4. Improvement of Copper Exposed on Silver Surface of Multilayer Circuit Board

All kinds of steps before silver immersion should be carefully supervised. For example, after micro etching the copper surface, pay attention to its "water break" inspection (water break refers to water repellency) and the observation of very bright copper spots, which all indicate that there will be some dirt on the copper surface. The clean copper surface with fine micro etching must stand for 40 seconds without water damage. The on-line machines and equipment should also be maintained on time to maintain their water solubility symmetry, so that a more symmetrical silver coating can be obtained. In actual operation, it is also necessary to continue to carry out experiments on the DOE test scheme for immersion barrel plating time, liquid temperature, mixing, diameter and size, so as to obtain the best quality silver coating. For the silver immersion process of thick steel plates with deep holes and HDI micro buried hole plates, the external force of ultrasonic wave and intensifier can also be used to help improve the spread of silver coating. The additional super strength mixing of the tank liquid can improve the working ability of wetting and exchanging the Yao water in the deep hole and the buried hole, which is very helpful for all wet processes.

5. Improvement of micro holes in spot welding of multilayer circuit board

Interfacial micro holes are still the defects that are difficult to be improved by silver immersion at this stage, because their real causes have not been revealed yet, but at least some related reasons can be determined. Therefore, in order to avoid the generation of related elements, the generation of welding micro holes in the middle and lower reaches can be reduced naturally.