How to Choose Ssurface Treatment Process
The choice of surface treatment process mainly depends on the type of final assembled components. The surface treatment process will affect the production, assembly and final use of PCB. The following will specifically introduce how to choose from five common surface treatment processes.
1. Hot Air Leveling
Hot air leveling used to be the dominant position in the PCB surface treatment process. In the 1980s, more than three-quarters of PCBs used hot air leveling processes, but the industry has been reducing the use of hot air leveling processes in the past ten years. It is estimated that about 25%-40% of PCBs currently use hot air. Leveling process. The hot air leveling process is dirty, unpleasant, and dangerous, so it has never been a favorite process, but hot air leveling is an excellent process for larger components and wires with larger spacing. In higher density PCBs, the flatness of hot air leveling will affect subsequent assembly. Therefore, HDI boards generally do not use hot air leveling processes. With the advancement of technology, hot air leveling processes suitable for assembling QFPs and BGAs with smaller pitches have emerged in the industry, but there are fewer practical applications. At present, some factories use organic coating and electroless nickel/immersion gold processes to replace the hot air leveling process. Technological developments have also led some factories to adopt tin immersion and silver immersion processes. Coupled with the lead-free trend in recent years, the use of hot air leveling has been further restricted. Although the so-called lead-free hot air leveling has appeared, this may involve equipment compatibility issues.
2. Organic Coating:
It is estimated that about 25%-30% of PCBs currently use organic coating technology, and the proportion has been rising (it is very likely that organic coating has now surpassed hot air leveling and ranks first). The organic coating process can be used on low-tech PCBs or high-tech PCBs, such as PCBs for single-sided TVs and boards for high-density chip packaging. For BGA, there are more applications of organic coating. If the PCB does not have functional requirements for surface connection or a limit on the storage period, organic coating will be the most ideal surface treatment process.
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