PCB HASL-What You Need To Know About

Abstract

PCB HASL stands for Hot Air Solder Levelling. Finished printed circuit board are usually coated with solder before and after placing the components to ensure the smooth connectivity and avoid the possibility of rough surface.

Content

1.PCB HASL

2.PCB HASL surface finish

3.PCB tinning solution

4.PCB HASL lead free

pcb hasl

 

1.PCB HASL

Before placing the components usually, the board is immersed into a molten solder bath to cover all the exposed copper spots. After the immersion to clean the irregular solder flow and hard spots HASL method is used. PCB HASL can also clean the rough edges in solder paste reflow.

 

2.PCB HASL surface finish

The principle of PCB HASL is very simple as the name implies. A gentle flow of hot air is blown over the printed circuit board to re-melt the solder and flow smoothly over the desired pads. The major advantage of doing the HASL is that it can resolver any irregular solder flow over the components which may affect the boards function especially the boards with tiny SMD packs.

 

The second advantage of blowing hot air over the finished boards is that it removes the uneven solder flow which in turn avoids trace short, unlevelled components placement, poor thermal conductivity for the power SMD components etc. It’s also very cost effective and re-processable.

 

pcb hasl

3.PCB tinning solution

People use PCB tinning solution or liquid tin  to coat a thin layer of thin on the copper pads to assist the soldering process of the PCB. This or the liquid tin contains dissolved tin and added flux and cleaning agents.It works by chemical displacement of the ion from copper and tin.

 

Since copper and tin share strong affinity to each other, this a simple step without the need of electrodes and electricity. Major advantage of the tinning process is that it avoids lead. Due to chemical deposition this process naturally yields even distribution of tin in turn resulting in a flat surface.

pcb hasl

 

4.PCB HASL lead free

HASL lead free is the most preferred surface finish method used in the PCB production as the PCB production guidelines and RoHS instructs strictly to remove hazarders material such as lead. While this method has the same method that include immersing PCB into molten tin/lead alloy.

 

Hot air jets removes the excess solder referred to as ‘air knives’. And lead free solder alloy is use for the lead-free boards. As lead free soldering method requires higher temperatures in the range above 260°C, PCB HASL lead free method avoids any potential solder re-flow defects and component displacement.

pcb hasl

 

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