Analysis on the Causes of Overflow of Adhesive in FPC Flexible Circuit Board Pressing

There are many reasons for the overflow of FPC flexible circuit boards, which are related to the FPC manufacturer's process parameters, storage environment, employee operation methods, and the processing process of the protective film (COVERLAY). Below, we will discuss specific factors:



1. Reasons for the parameters of the protective film (COVERLAY) during the manufacturing process



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



2. Overflow of protective film and storage environment reasons



At present, the storage conditions for Taihong COVERLAY are below 10 ℃, with the optimal storage temperature ranging from 0 ℃ to 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.



3. Whether the customer's product structure is reasonable is an important reason for the overflow phenomenon



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. Therefore, errors in the structural combination of FPC flexible circuit boards should be avoided from the source.



4. The special design of FPC flexible circuit board products can also cause local adhesive overflow



With the emergence of high-precision products, independent PAD positions have been designed in some FPC flexible circuit board products. During the pressing and heating process, due to the absence of voids around it, the smaller the PAD position, the more obvious the phenomenon of adhesive overflow.



5. Causes of overflow and process parameter settings in FPC flexible circuit board factories



In the setting of process parameters, if the pressure is too high, the time is too long, and the pressure of the press is uneven, it may lead to glue overflow. In addition, the control of overflow is also related to the adhesive absorption performance of the auxiliary materials used for hot pressing.