Cause of blistering problem on board

- Nov 03, 2018-

Bubbling on the board surface is actually a problem of poor adhesion of the board surface, which is also a problem of the surface quality of the board surface, which contains two aspects:

Cleanliness of the board;2. Surface roughness (or surface energy).

All blistering problems on the board can be attributed to the above reasons.

Due to poor or low adhesion between the plating layers, it is difficult to resist the plating stress, mechanical stress and thermal stress generated during the subsequent production and assembly processes, resulting in different degrees of separation between the plating layers.

Some factors that may cause the poor quality of the board surface in the production and processing are summarized as follows:

Problems of substrate processing:

Especially for some thin substrate (generally 0.8mm below), because of the poor rigidity of the substrate, it is not appropriate to brush the plate with the machine.

So may be unable to effectively remove the substrate in order to prevent the surface oxidation of copper foil in the process of production and processing and special processing layer, while the layer is thinner, brush plate is easy to remove, but the chemical processing is difficult, so the important note in production and processing control, lest cause panel substrate copper foil and copper chemical bonding force between the surface bubbles caused by bad;When the thin inner layer is blackened, there will be some problems such as black Browning, uneven color, and partial black Browning.

2. Poor surface treatment caused by oil pollution or dust contamination of other liquids caused by surface machining (drilling, lamination, edge milling, etc.).

3. Bad copper brush plate:

The pressure of the grinding plate before the copper deposit is too high, causing the orifice deformation. Brush out the orifice copper foil rounded corners and even the orifice leakage of the base material. In this way, the foaming phenomenon of the orifice will occur in the process of electroplating the copper deposit and soldering tin.Even if the brush plate does not cause the base material to leak, but the oversize brush plate will increase the roughness of the hole copper, so the copper foil in the process of micro-corrosion coarsening will easily produce the over-coarsening phenomenon, there will also be some quality hidden trouble.Therefore, it is necessary to strengthen the control of the brush plate technology. The parameters of the brush plate can be adjusted to the best through grinding mark test and water film test.

4. Washing problem:

Want because of heavy copper electroplating processing through a large number of chemical liquid medicine processing, all kinds of acid-base the non-polar organic solvent such as drugs, board face wash not clean, especially heavy copper adjustment in addition to the agents, not only can cause cross-contamination, also will cause the board face local processing bad or poor treatment effect, the defect of uneven, cause some of the binding force;Therefore, the control of water washing should be strengthened, mainly including the control of water flow, water quality, water washing time and water dripping time of the board.Especially in winter, when the temperature is low, washing effect will be greatly reduced.

5. Microcorrosion in pre-processing of heavy copper and electroplating of graphics:

Excessive microerosion may cause the hole to leak the base material and cause the bubble around the hole.The lack of microerosion will also lead to the lack of binding force and cause the bubbling phenomenon.Therefore, the control of microerosion should be strengthened.Generally, the microcorrosion depth before copper deposition is 1.5--2 micron, and the microcorrosion before electroplating is 0.3--1 micron. Under certain conditions, it is better to control the microcorrosion thickness or the corrosion rate by chemical analysis and simple test weighing method.Generally, the plate surface after microetching is bright color, uniform pink, no reflection;If the color is not uniform, or there is reflection indicates that there is quality hidden trouble before processing;Pay attention to strengthening inspection;In addition, the content of copper, the temperature of the bath, the load capacity, and the content of microetchant are all items that should be paid attention to.

6. Poor rework of heavy copper:

Some rework plates which are made of heavy copper or have been converted to graphics may cause blistering in the rework process due to improper shedding, incorrect rework method or improper control of microetching time in the rework process.If rework of heavy copper plate is found on the line, bad copper can be directly removed from the line after washing and pickling without direct rework.It is better not to remove oil again, micro-corrosion;For the plate parts that have been electrically thickened, the microetch groove should be taken off now. Note the time control. One or two plates can be used to roughly calculate the time of the plate, so as to guarantee the effect of the plate.After the plating is finished, a set of soft and abrasive brushes are applied and then copper is deposited according to the normal production process.

7. Panel surface oxidized during production:

If the copper sheet oxidizes in the air, it may not only cause no copper in the hole, the surface of the board is rough, but also cause the board surface to bubble.The copper sheet is stored in the acid solution for a long time, and the surface of the plate will also oxidize, and this oxide film is difficult to remove.Therefore, in the production process, the copper plate should be thickened in time, and the storage time should not be too long. Generally, the copper plating should be thickened within 12 hours at the latest.

8. The activity of heavy copper solution is too strong:

The high content of three components, especially the high content of copper in the newly opened cylinder or tank, will lead to the excessive activity of the tank, rough chemical copper deposition, excessive inclusion of hydrogen and cuprous oxide in the copper layer, resulting in decreased physical quality of the plating layer and poor adhesion.The following methods can be adopted appropriately: reducing the content of copper (adding pure water to the bath), including three components, appropriately increasing the content of complexing agent and stabilizer, and appropriately reducing the temperature of the bath, etc.;

9. Insufficient washing water after developing in the process of graphics transfer, prolonged storage time after developing or excessive dust in the workshop will lead to poor cleanliness of the board surface and slightly poor fiber treatment effect, which may lead to potential quality problems;

10. Organic pollution, especially oil pollution in electroplating tank, is more likely to occur in automatic line;

11. Please pay attention to the timely replacement of the soaking tank before copper plating. Too much pollution in the tank liquid or too high copper content will not only cause the cleanliness of the board surface, but also cause the defects such as rough board surface.

12. In addition, in winter, when there is no heating of the tank liquid in some factories, special attention should be paid to the electrification of the plates in the production process, especially the plating tank with air stirring, such as copper nickel.For the nickel cylinder in winter, it is better to add a warm water bath before nickel plating (water temperature is around 30-40 degrees) to guarantee the density of initial nickel deposit is good.

In the actual production process, there are many reasons for blistering on the board surface. The author can only make a brief analysis. For different equipment technology level of different manufacturers, blistering phenomena may occur due to different reasons.The above reasons are of no importance and importance, and a brief analysis is basically made according to the production process. In this series, it only provides you with a direction to solve the problem and a broader vision. I hope that your process production and problem solving can play a role in attracting valuable talents.