Bubbles and overflow are common quality anomalies in the lamination process of flexible circuit boards. Overflow refers to the problem of adhesive stains on the PAD position of the FPC circuit, similar to the EXPORY series, caused by the increase in temperature during the lamination process, resulting in the flow of the adhesive system in COVERLAY.

There are many reasons for overflow, which are related to the processing flow of the protective film (Coverlay); It is related to the process parameters, storage environment, and employee operation methods of the FPC factory. Below, we will discuss specific factors:

One of the specific factors that cause glue overflow is determined by the parameters during the COVERLAY manufacturing process.

When CL enters the drying stage after coating, improper control of temperature, time and other parameters can lead to excessive flow rate of the adhesive system during the semi curing process. In addition, if the CL adhesive system is unevenly distributed during coating, it is difficult to control the amount of adhesive overflow during the pressing process.

When such products are shipped to customers, the amount of overflow during incoming inspection will be significantly higher than the indicated value on the product specifications.

2. The specific factor that causes overflow is related to the storage environment.

At present, the storage conditions for Taihong COVERLAY are below 10 ℃, with the optimal storage temperature of 0 ℃ -5 ℃ and a storage time of 90 days.

If the storage time is exceeded or the storage conditions do not meet the requirements, COVERLAY is prone to moisture absorption in the air, resulting in unstable adhesive system and easy overflow.

The third specific factor that causes glue overflow is whether the customer's product structure is reasonable, which is an important reason for the phenomenon of glue overflow.

In the product design process, the combination of FCCL and CL should be as reasonable as possible. If the thickness of the Coverlay adhesive system is significantly different from the thickness of the substrate copper foil, there is a high possibility of adhesive overflow. Errors in FPC structure matching should be avoided from the source.