For some customers, lead-free FPC assembly is not necessary. Therefore, when they need customized FPC assembly services, they may be confused about whether lead-free FPC assembly or lead assembly should be used on their products. The following introduction may help customers choose the right method.
Firstly, customized lead-free FPC assembly is mainly environmentally friendly, healthier for users, and has much less impact on the environment. So if the product needs to meet RoHS and REACH requirements, customers must choose lead-free FPC assembly. However, due to the higher price of lead-free solder, the assembly cost of lead-free FPC assembly is slightly higher than that of lead assembly. So for customers, it's better to consider environmental policies, prices, and product profits rather than blindly pursuing lead-free soldering.
The lead-free soldering temperature is about 35 degrees higher than the lead soldering temperature. During SMT assembly, the soldering temperature is also higher than the Tg of the FPC substrate, and the lead-free soldering temperature is higher than the lead soldering temperature. If the TG of the FPC material is too low, it is easy to cause FPC thermal deformation and component damage during cooling. Therefore, FPC materials with higher Tg should be selected appropriately.
The lead-free soldering process requires FPC to have good heat resistance, high glass transition temperature Tg, low thermal expansion coefficient, and low cost. Therefore, it is necessary to consider the impact of high temperature on component packaging. Due to the fact that the packaging material of traditional surface mount components can meet the soldering temperature of lead solder as long as it can withstand 240 degrees Celsius, while the soldering temperature of complex products during lead-free soldering can reach 260 degrees Celsius, it is necessary to consider whether the packaging of components can withstand high temperatures.
In addition, the impact of high temperature on the internal connections of the device should also be considered. The internal connection methods of ICs include gold wire ball welding, ultrasonic pressure welding, and reverse welding, especially for new electronic components such as BGA, CSP, composite components, modules, etc. The materials used for internal connections are the same as the solder used for surface assembly, and they also use reflow soldering technology.
From a cost perspective, the cost of lead-free solder currently developed is higher than that of tin lead alloys. Many people may think that the cost of solder material accounts for a high proportion. However, according to some statistical data, FPC manufacturers generally control the cost of solder within 10% of the total cost, especially for technical electronics/FPC, so it will not have a significant impact on the overall cost of the final product. Therefore, most customers choose lead-free FPC assembly in their RoHS compliant FPCs.
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