Phenomenon signs: significantly different laminate colors, different surface color, surface or lining a smudge, laminate surface, there are various colors of thin 
Inspection methods can be used: visual.

Possible reasons: 
1. Glass cloth laminated board in the process before or after etching the surface of white Gyrosigma or white spots. 
2. After processing technology, the surface of white or more of the exposed glass cloth. 
3. After processing by the process, especially in the soldering, the surface has a thin white film, indicating that erosion is a resin or a mild deposition of foreign material. 
4. Substrate color change may be acceptable to look beyond the requirements. 
5. As the laminate by overheating or excessive concentrations of some syrup too long soak, the substrate the appearance of brown or brown markings.

Solution: 
1. In very few cases, because of the lack of resin surface, revealing a glass cloth, which is rare today. Is more often seen on the surface of tiny white blisters or small hole. This is because the surface coating layer of glass cloth and resin systems caused by the reaction. Exposed many of the glass cloth board, increase in humidity, the surface resistance decreased. However, small blisters or small bubble with the board is usually not decreased. Strictly speaking, this is a problem looks to deal with the laminate manufacturer, to avoid recurrence of such problems; and to determine an acceptable internal standard small blisters. 
2. The process after processing the vast majority of exposed glass cloth is solvent erosion due to the exception of some surface resin. Together with the laminate manufacturer's inspection of all the solvent and electrolyte, particularly laminates each solution in the time and temperature to ensure that they apply to the use of laminates. Where possible, in accordance with the conditions recommended by laminate manufacturer processing. 
3. And laminate manufacturer with checks to ensure the use of flux is applied to the plate used. Authentication may be deposited on a mineral or inorganic processes, may be deposited in a mineral or inorganic processes, where possible, try to use in addition to mineral water. 
4. Laminates manufacturer, laminated sheets to ensure that any major component or resin (their color it) before making a change authorized user. Sometimes too much transfer will affect the color of copper alloy. Dealing with the laminated board manufacturer to determine the scope of acceptable appearance. 
5. Check dip soldering operation, solder in the solder bath temperature and the stop time. Also check the heating elements on the PCB or the PCB temperature. If the latter exceeds the laminated sheets used to allow the maximum temperature of the substrate will produce brown. Subject to certain solution concentration is too high for too long after soaking the plate in the heating process when the test board shown, check the control solution concentration and time.