1. The cleanliness of the PCB circuit board surface;
2 The problem of surface micro-roughness (or surface energy).
The board surface blistering problem on all circuit boards can be summarized as the above reasons.
The bonding force between the coatings is poor or too low, and it is difficult to resist the coating stress, mechanical stress and thermal stress generated during the production and processing process in the subsequent production and assembly process, which eventually leads to different degrees of separation between the coatings.
Some factors that may cause poor board surface quality in the production and processing process are summarized as follows:
1. The problem of pcb base material process treatment:
Especially for some thinner substrates (generally less than 0.8mm), because the rigidity of the substrate is poor, it is not suitable to use a brushing machine to brush the board.
This may not be able to effectively remove the protective layer specially treated to prevent the oxidation of the copper foil on the board surface during the production and processing of the substrate. Although the layer is thin, it is easier to remove the brush board; It is important to pay attention to the control of processing so as not to cause board surface blistering caused by poor bonding between the substrate copper foil and chemical copper. This problem also occurs when the thin inner layer is blackened, and blackening and browning defects also exist. Uneven color, local black and brown, etc.
2. Poor surface treatment caused by oil or other liquid contamination and dust contamination on the surface of the circuit board during machining (drilling, lamination, milling, etc.).
3. Bad rework of sinking copper:
Some sinking copper or reworked boards after graphics transfer will cause blisters on the board surface due to poor deplating, incorrect rework methods, improper control of micro-etching time during rework, or other reasons; if the rework of sinking copper boards is found online Defective copper sinking can be directly removed from the line after washing with water, then pickled and reworked directly without corrosion; it is best not to re-degrease and micro-etch; for the plate that has been thickened, it should be deplated in the micro-etch tank, pay attention For time control, one or two boards can be used to roughly calculate the deplating time to ensure the deplating effect; to halve or make necessary adjustments;
4. Washing problem:
Because the electroplating treatment of copper sinking needs to be treated with a large amount of chemical medicine. There are many chemical solvents such as various acids, bases, non-polar organics, etc., and the surface of the board cannot be washed with water, especially the adjustment of degreasing agent for copper sinking, which will not only cause cross contamination Partial surface treatment is poor or the treatment effect is not good; uneven defects cause some bonding problems; therefore, attention should be paid to strengthening the control of water washing, mainly including the water quality of washing water flow, washing time, and plate dripping time, etc. The control of washing; especially in winter when the temperature is low, the washing effect will be greatly reduced, and more attention should be paid to the control of washing;
5. Immersion copper brush plate is bad:
The pressure of the grinding plate before sinking copper is too high, which will cause the hole to deform and brush out the rounded corners of the copper foil at the hole or even the base material of the hole, which will cause blistering at the hole during the process of copper sinking, electroplating, tin spraying and welding; even if brushing The plate does not cause leakage of the base material, but an overweight brush plate will increase the roughness of the copper at the orifice. Therefore, during the process of micro-etching and roughening, the copper foil at this place is prone to excessive roughening, and there will also be a certain quality. Hidden dangers; therefore, attention should be paid to strengthening the control of the brushing process, and the parameters of the brushing process can be adjusted to the best through the wear mark test and the water film test;
6. The activity of the copper precipitation solution is too strong:
Newly opened tank of copper sinking solution or the content of the three major components in the bath solution is too high, especially the copper content is too high, which will cause the bath solution to be too active. Chemical copper deposits rough , cuprous oxides, etc., and there are too many inclusions in the chemical copper layer. Defects of physical property quality decline and poor bonding force of the plating layer; the following methods can be adopted appropriately; reduce the copper content (add pure water to the bath) including three major components, appropriately increase the content of complexing agent and stabilizer, and appropriately reduce bath temperature, etc.;
7. The surface of the board is oxidized during the production process:
If the sinking copper board is oxidized in the air, not only may there be no copper in the hole, and the board surface may be rough; This kind of oxide film is difficult to remove; therefore, the sinking copper plate should be thickened in time during the production process. It should not be stored for too long. Generally, the copper plating should be thickened within 12 hours at the latest;
8. Micro-etching in the pre-treatment of copper sinking and the pre-treatment of graphic electroplating:
Excessive micro-etching will cause the substrate to leak from the orifice, resulting in foaming around the orifice; insufficient micro-etching will also cause insufficient bonding force and cause foaming; therefore, it is necessary to strengthen the control of micro-etching; generally micro-etching before copper deposition The depth is 1.5-2 microns, and the micro-etching is 0.3-1 microns before pattern electroplating. It is better to control the micro-etching thickness or the etching rate by chemical analysis and simple test weighing method; under normal circumstances, the color of the plate surface after micro-etching Bright, uniform pink, no reflection. If the color is uneven, or there is reflection, it means that there is a quality hazard in the pre-processing of the process; pay attention to strengthen inspection; in addition, the copper content of the micro-etching tank, the temperature of the bath, the loading capacity, and the content of the micro-etching agent, etc. is the item to note;
9. Insufficient water washing after development during the graphics transfer process, too long storage time after development or too much dust in the workshop, etc., will cause poor cleanliness of the board surface, and poor fiber treatment effect may cause potential quality problems;
10. Organic pollution in the electroplating tank, especially oil pollution, is more likely to appear in the automatic line;
11. Before copper plating, the acid dipping tank should be replaced in time. Too much pollution in the bath, or the copper content is too high, will not only cause problems with the cleanliness of the board surface, but also cause defects such as rough board surface;
12. In addition, when the tank liquid is not heated in some factories in winter, it is necessary to pay special attention to the electrification of the plates during the production process, especially the plating tank with air stirring, such as copper-nickel; for nickel tanks, it is best in winter Add a heated water washing tank before nickel plating (the water temperature is about 30-40 degrees), to ensure that the initial deposition of the nickel layer is dense and good.
