Board surface blistering is one of the more common quality deficiencies in the production process of circuit boards. Due to the complexity of the circuit board production process and the complexity of process protection, especially in chemical wet treatment, it is necessary to prevent and compare the lack of board surface blistering. difficult. On the basis of years of actual production experience and service experience, we are now making a brief and concise analysis of the causes of blistering on the surface of the circuit board immersed copper electroplating. The effect of throwing bricks and attracting jade!
The blistering on the surface of the circuit board is actually the problem of poor bonding strength of the board surface, and the extension is also the problem of the appearance quality of the board surface. This surface contains two internal substantive meanings:
a. The cleanliness of the board surface;
b. The problem of surface microscopic smoothness (or surface performance); the blistering problem on the board surface on all circuit boards can be summarized as the above-mentioned end by. The bonding force between the coatings is not good or too low, and the subsequent production and processing During the process and assembly process, it is not easy to resist the coating stress, mechanical stress and thermal stress, etc., which are generated during the production and processing, and finally lead to different degrees of clutch phenomenon between the coatings.
Now there are some factors that may lead to the poor quality of the board surface in the production and processing process, which are summarized as follows:
1. The problem of substrate processing; especially for a thin substrate (generally below 0.8mm), due to the poor rigidity of the substrate, it is not suitable to use a brushing machine to brush the plate, so there may be no way to remove it. Remove the best care layer that is specially treated to avoid oxidation of the copper foil on the board during the production and processing of the substrate. Although the layer is thin, the brush plate is easier to remove and remove, but it is difficult to use chemical treatment when it is considered appropriate. Therefore, attention should be paid to restraint in production and processing, so as to avoid the problem of board surface blistering caused by poor bonding force between the copper foil of the board substrate and chemical copper; this problem will also exist when the thin inner layer is blackened. The blackening and browning is not good, the color is uneven, and the partial blackening and browning is not equal to the problem of high grade.
2. The surface of the board is not handled properly due to oil or other liquid contamination and dust pollution caused by the process of machining (drilling, lamination, milling, etc.).
3. The copper sinking brush plate is not good: the pressure of the grinding plate before the copper sinking is too large, which leads to the deformation of the orifice and the rounded corners of the copper foil of the orifice or even the leakage of the base material in the orifice. This will lead to orifice blistering; even if the brush plate does not cause leakage of the substrate, the overweight brush plate will increase the smoothness of the copper in the orifice, so the copper foil is easily roughened during the micro-etching and roughening process. Excessive phenomenon, there will also be a certain quality hidden danger; because this should pay attention to strengthening the control of the brushing process, you can adjust the parameters of the brushing process to the best through wear scars and water film attempts;
4. Washing problem: Since copper sinking electroplating needs to be treated with a large number of chemical solutions, various acid-base, non-polar organic and other chemical solvents are more, and the surface of the board cannot be washed cleanly, especially the copper sinking debugging and degreaser, which will not only cause damage. If the transaction is successful, the fork contamination will also lead to the poor disposal of the board surface or the poor disposal effect, and the lack of uniform warping edges, which will lead to a little problem in terms of bonding force; because this should pay attention to strengthening the control of water washing, mainly covering the cleaning water flow. Control of water quantity, water quality, washing time, and board dripping time; especially in winter when the air temperature is low, the washing effect will be greatly reduced, and more attention should be paid to the control of washing;
5. Micro-etching in the pre-treatment of copper sinking and pattern plating; excessive micro-etching will lead to leakage of the base material from the orifice, resulting in blistering around the orifice; insufficient micro-etching will also lead to insufficient bonding force, leading to Bubble phenomenon; because this is to enhance the control of micro-etching; the depth of micro-etching before ordinary copper sinking is 1.5-2 microns, and the micro-etching before pattern plating is 0.3-1 microns, and it is best to pass Chemical analysis and simple weighing method control micro-etching thickness or corrosion efficiency; under normal operating conditions, the surface of the board after micro-etching is bright and glossy, with an average pink color and no reflection; if the color is uneven, or there is reflection, explain the process There is a hidden quality risk in the pre-treatment; pay attention to strengthening the inspection; the copper content of the additional micro-etching tank, the temperature of the bath, the load, the content of the micro-etching agent, etc. are all items to be paid attention to;
6. Oxygenation occurs on the board surface during the production process; if the copper immersion board is oxidized in the air, it may not only lead to no copper in the hole, the board surface is not delicate, but also may cause the board surface to foam; If the storage time in the liquid is too long, oxygen oxidation will also occur on the surface of the board, and this oxygen oxide film is difficult to remove; because the copper sink plate should be thickened as soon as possible during the production process, it is not suitable for storage and placement for too long. Generally, the copper plating should be thickened within 12 hours at the latest;
7. The copper sinking is not good; the reworked board after a little copper sinking or pattern transfer is not well plated during the reworking process, the reworking method is wrong or the micro-etching time is inappropriate during the reworking process, etc. or other reasons. This will cause the board surface to foam; if the refurbishment of the copper sinking board finds that the sinking copper is not good on the line, it can be washed with water and then directly removed from the line. ;For the plate that has been thickened by the board, it should be stripped in the micro-etching tank. Pay attention to time control. You can use one or two pieces of board to measure the stripping time at once to ensure the stripping effect. After stripping, use brushing A group of gentle entanglement brushes at the back of the machine are lightly brushed, and then copper is deposited according to the normal production process, but the time for etching and micro-etching should be halved or indispensable debugging;
8. Organic pollution, especially oil pollution, is exposed in the electroplating tank, which is more likely to be exposed in the semi-automatic line;
9. Before copper plating, the pickling tank should be changed as soon as possible. There is a lot of pollution in the tank solution, or the copper content is too high, which will not only cause problems with the cleanliness of the board surface, but also cause the board surface to be not delicate and other defects;
10. Insufficient water washing after development in the process of image transfer, too long storage time after development or too much dust in the workshop, etc., will lead to poor cleanliness of the board surface and poor fiber disposal effect, which may lead to potential quality problems;
11. In addition, when the tank liquid is not heated during the production of the factory in winter, it is necessary to pay more attention to the electrification of the board during the production process, especially the plating tank with air mixing, such as copper-nickel; it is best for nickel cylinders in winter Add a warm water washing tank before nickel plating, (the water temperature is about 30-40 degrees), to ensure that the nickel layer is deposited for a period of time at the beginning of the deposition, which is meticulous and precise;
In the actual production process, there are many reasons that cause the foaming of the board surface. The author can only make a brief and brief analysis. For different manufacturers' facilities and technical standards, it may reveal the phenomenon of foaming caused by different reasons, and the specific working conditions To analyze in detail, it is not possible to discuss them all together, and to copy them; the above-mentioned end-by-point analysis is not divided into primary and secondary and critical, basically according to the production process flow to do a simple and brief analysis, in this series, just to provide you with a solution The direction of the problem and a broader vision, the specific situation depends on the situation at the scene.
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