Analysis of Printed Circuit Board HASL Process
What is the surface treatment method of PCB board hasl?
HASL is the abbreviation of hot air solder leveling. In the PCB industry, it refers to the surface treatment method of exposed copper foil, namely: lead spray tin. (HASL-LF when lead-free spray tin)
HASL is the main lead surface treatment process used in industry. The process consists of immersing the circuit board in a lead-tin alloy, and the excess solder is removed by an "air knife". The so-called air knife is hot air blowing on the surface of the board. For the PCA process, HASL has many advantages: it is the cheapest PCB, and the surface layer can be soldered after multiple reflow soldering, cleaning and storage. For ICT, HASL also provides a process for automatically covering test pads and vias with solder. However, compared with the existing alternative methods, the flatness or coplanarity of the HASL surface is poor. Now there are some lead-free HASL alternative processes, which are becoming more and more popular due to the natural replacement characteristics of HASL. For many years, HASL has been applied with good results, but with the emergence of "environmentally friendly" green process requirements, the existence of this process is numbered. In addition to the lead-free problem, increasing board complexity and finer pitch have exposed many limitations of the HASL process. Advantages: The lowest cost PCB surface technology, maintains solderability throughout the manufacturing process, and has no negative impact on ICT. Disadvantages: Usually lead-containing processes are used. Lead-containing processes are now restricted and will eventually be eliminated by 2007. For fine pin spacing (<0.64mm), it may cause solder bridging and thickness problems. Uneven surface can cause coplanarity problems in the assembly process
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