Bubbles and glue are a common quality abnormal phenomenon in the process of flexible circuit board.
First of all, let's understand what the glue overflow is Bubbles and glue are a common quality abnormal phenomenon in the process of flexible circuit board.Overoverflow is in the compression process, the temperature increases in the COVERLAY The glue system flows, resulting to the EXPORY series in the PAD position of the FPC line. Two, let's discuss the causes of glue overflow There are many reasons for glue overflow, related to the processing process of protective film (COVERLAY), process parameters, preservation environment and staff operators of FPC plant There has a relationship.Below, to discuss from the specific factors:
1.One of the specific factors of glue overflow: it is determined by the parameters in the COVERLAY manufacturing process. When CL is coated (COATING) into the drying stage, if the temperature, time and other parameters are not properly controlled, the glue system flow in the semi-curing process is too large.In addition, such as The distribution of fruit CL glue system is not uniform, and it is difficult to control the overflow amount during the process of pressure closing. When such products are shipped to the customer, the glue overflow amount is significantly higher than the value indicated in the product specification. 2. The second specific factors of glue overflow: COVERLAY glue overflow is related to the storage environment. At present, the storage condition of hong COVERLAY is less than 10℃, the best storage temperature is 0℃ -5℃, and the storage time is 90 days. If the storage time is exceeded or the storage conditions do not meet the requirements, COVERLAY is easy to absorb moisture in the air and lead to the glue system instability, and it is easy to produce the glue overflow. 3. The specific factors of glue overflow: whether the customer product structure is reasonable is an important reason for the phenomenon of glue overflow. In the product design process, FCCL and CL collocation should be as reasonable as possible.If the thickness of COVERLAY glue system is larger from the thickness of substrate copper foil, it is very likely to overflow Rubber phenomenon.The mistakes of FPC structure collocation should be avoided from the source. 4. Four specific factors of glue overflow: the special design of the customer FPC finished product will also lead to local glue overflow. With the advent of high-precision products, in certain FPC products, independent PAD bits are designed.In the process of pressure and heating, the smaller the PAD overflow, the more obvious because there is no space around it.During the pressure closing and false connection, the operation mode has a direct impact on the staff and the glue overflow. The protective membrane CL and substrate FCCL align imprecisely during pseudobonding 5. Five specific factors of glue overflow: the production of glue overflow is related to the process parameters of FPC factory. In the setting of process parameters, if the pressure is too large, the time is too long, and the compressor pressure is uneven, it may lead to the glue overflow phenomenon.In addition, the control of overflow glue and hot pressure with side material The suction adhesive performance is related. Third, discuss the solution of glue overflow We have known the cause of glue overflow before, so we can apply the appropriate medicine, according to the specific situation, put forward different solutions. Solution for glue spill: The glue is caused by the manufacture of COVERLAY. Then, FPC manufacturers should strictly material inspection, if in the material sampling inspection, the glue exceeds the standard, contact the supplier to return, otherwise it is difficult to control in the production process. Overoverflow is caused by the storage environment.
Because the quality assurance time of protective film (CL) is short (the storage period of FPC manufacturer is generally less than two months), so customers need to make an assessment when purchasing, and do not use expired products as far as possible. FPC manufacturers had better set up a special refrigerator to preserve the protective film.If the CL glue system is damp due to the preservation conditions not meeting the requirements, the CL can be pre-baked at low temperature, (60-80℃; 2 -4 Hours) can improve the overflow amount of CL to a large extent.In addition, the CL that is not used up on that day needs to be put back to the refrigerator in time. Local glue overspill caused by independent small PAD positions This phenomenon is one of the most common quality abnormalities encountered by most FPC manufacturers in China.If the process parameters are changed simply to solve the spill, bubbles or stripping Insufficient intensity, such as new problems.Only the process parameters can be adjusted reasonably. The smaller the independent PAD position, the more difficult the glue overflow amount is to control.At present, some domestic methods are to use special brush brush to smear the glue stains on the PAD position, and then wipe them with eraser. If the glue overflow is not controlled properly controlled, a large area of glue can be soaked in about 2% NaOH solution for 3-5 minutes, and then the glue can be worn off after the brush.(Note: The PI is intolerant Strong alkali, not soak too long, otherwise FPC finished product becomes larger) Overoverflow caused by operation mode During the false connection, employees should be required to accurately align, correct the counterpoint fixture, and increase the intensity of the counterpoint check.Avoid glue overflow due to misalignment. At the same time, do the "5S" work in the pressure and false contact, prior to check whether the protective film CL is contaminated, whether there is a margin, if there is a need to remove the protective film margin.Training staff To develop good operation habits, is conducive to improving the rate of product quality. Overm overflow caused by FPC plant process. If the press is used, then appropriately extend the prepressure time, reduce pressure, reduce temperature, reduce pressure time, are conducive to reduce the overflow.If the pressure of the press is not Uniform, can use induction paper to test the press pressure is uniform, can contact the fast press supplier to debug the machine and equipment.Choose the film with good suction performance Glass fiber cloth, add silicone gasket, is an important way to improve the excessive amount of glue overflow. Improvement measures of traditional compressor: (1) At present, the Taiwan rainbow rheological test mainly increases the time of rising temperature and fixed temperature.(Pressure part should not be tested at present) (2) It can be seen from the figure above, that the maximum flow temperature of iris CL (protective film) is 115℃, if the immediate upper pressure may cause the maximum glue overflow, and can reach the best Fill the glue point. (3) After the elasticity and viscosity are 108~123℃, the flow from the diagram is slowly deteriorated, so if the pressure overflow is too large, the upper pressure closing point can be extended to 123℃ and then the upper section Pressure, can improve the glue overflow problem, or repressure transmission prepressure time is extended.
