Surface treatment in PCB industry (HAL and LFHAL)

With the continuous improvement of the living environment, the environmental issues involved in PCB production are getting more and more attention, especially Lead and Bromine.

The basic purpose of PCB surface treatment is to ensure good weldability and electrical performance. Because the copper is unlikely to remain the original for a long time exposed in the air, so the copper surface needs to be treated to avoid oxidization.

Now there are many PCB surface treatment types applications, the common types are HAL/LF-HAL, OSP, flash gold, hard gold, immersion tin, immersion silver, ENEPIG, and so on. Let’s check them out!

1.Hot air level and Lead-free hot air level

The general process of the HAL/LF-HAL process is micro erosion — preheating — coating flux — HAL/LF-HAL — cleaning.

Hot air leveling is the process of coating molten tin solder on PCB surface and heating compressed air,to form a coating of both anti-oxidation and good weldable on the copper surface.

HAL/LF-HAL is divided into two types: vertical and horizontal. Generally, it is considered that the horizontal type is better, which is mainly composed of horizontal hot air leveling coating, which can realize automatic production.

Merits: Longer storage time; Completely covered with tin before welding; Suitable for lead-free soldering; Mature process, low cost, suitable for visual inspection and electrical measurement.

Demerits: Not suitable for bonding; Due to the surface flatness problem, there are also limitations on SMT; Not suitable for contact switch design.PCBs undergo a high temperature while spraying tin, which may cause the copper to dissolve.

(To be continued…)