What is the cause of blistering on the circuit board surface? -

What is the cause of blistering on the circuit board? Release time: 2017-12-12 0 The blistering of the circuit board surface is actually a problem of poor bonding force of the board surface, and then it is the surface quality problem of the board surface, which contains two aspects: 1. The cleanliness of the board surface Problems; 2. The problem of surface micro-roughness (or surface energy). The blistering problem on all circuit boards can be summarized as the above-mentioned 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 in the production process during the subsequent production process and assembly process, which will eventually cause different degrees of separation between the coatings. Some factors that may cause poor board quality in the production process are summarized as follows: 1. The problem of substrate processing: Especially for some thinner substrates (generally less than 0.8mm), because the rigidity of the substrate is relatively high. Poor, it is not suitable to use a brushing machine to brush the board. In this way, it may not be possible 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 and the brush is easier to remove, it is difficult to use chemical treatment. It is important to pay attention to control during processing, so as to avoid the problem of blistering on the board caused by poor bonding between the copper foil of the board substrate and the chemical copper; this problem will also cause blackening and browning when the thin inner layer is blackened. Poor, uneven color, partial black browning and other problems. 2. The phenomenon of poor surface treatment caused by oil stains or other liquids contaminated with dust during machining (drilling, lamination, milling, etc.) 3. Poor sinking copper brush plate: The pressure of the sinking copper front grinding plate is too large, causing the hole to be deformed, brushing out the hole copper foil rounded corners and even the hole leaking the base material, which will cause the sinking copper electroplating, spraying tin welding and other processes. Foaming phenomenon at the orifice; even if the brush plate does not cause leakage of the substrate, the excessively heavy brush plate will increase the roughness of the orifice copper, so the copper foil at this place is prone to excessive roughening during the microetching process , There will also be certain hidden quality hazards; therefore, we must pay attention to strengthen the control of the brushing process, and the brushing process parameters can be adjusted to the best through the wear scar test and the water film test; 4. The problem of water washing: plating treatment for copper It has to go through a lot of chemical treatments. There are many chemical solvents such as various acid, alkali, non-polar organic and so on. The board surface is not clean with water, especially the copper immersion adjustment degreasing agent, which will not only cause cross-contamination, but also cause poor local treatment of the board surface. Or the treatment effect is not good, uneven defects, causing some binding problems; therefore, attention should be paid to the control of washing, mainly including the control of washing water flow, water quality, washing time, and plate dripping time. ; Especially in winter when the temperature is low, the washing effect will be greatly reduced, and more attention should be paid to the strong control of washing; 5. Micro-etching in the pre-treatment of copper sinking and pattern plating: Excessive micro-etching will cause the hole to leak the substrate , Resulting in blistering around the orifice; insufficient micro-etching will also cause insufficient binding force and cause blistering; therefore, it is necessary to strengthen the control of micro-etching; generally the depth of micro-etching before copper sinking is 1.5---2 microns, The micro-etching in the pre-treatment of pattern electroplating is 0.3--1 microns. If possible, it is better to control the thickness of the micro-etching or the etching rate through chemical analysis and simple test weighing method; under normal circumstances, the color of the plate surface after micro-etching is bright and uniform. Pink, no reflection; if the color is uneven, or there is reflection, it means that there is a hidden quality problem in the pre-processing; pay attention to strengthen the inspection; in addition, the copper content of the micro-etching tank, the temperature of the bath, the load amount, the content of the micro-etching agent, etc. must be paid attention to 6. Poor rework of copper sinking: Some copper sinking or reworked boards after pattern transfer may cause the board surface to rise due to poor fading, improper rework methods or improper control of the micro-etching time during the rework process or other reasons. If the rework of the heavy copper plate is found on the line, you can directly remove the oil from the line after washing with water and then directly rework without corrosion after pickling; it is best not to re-degrease or micro-etch; for the plate that has been thickened by electricity The parts should be deplated in the micro-etching tank. Pay attention to the time control. You can first use one or two plates to roughly measure the deplating time to ensure the deplating effect; after the deplating is completed, apply a set of soft brushes and lightly brush after the brushing machine. Immerse the copper according to the normal production process, but the corrosion time should be halved or adjusted if necessary;