PCBA for non-contact infrared thermometer

What is HASL?

Apr 09, 2021

HASL,Hot-air solder leveling (also somebody call spray tin), a process in which lead-tin solder is applied (melted) on the surface of the PCB, and the lead-tin solder is blown flat with heated compressed air. (In the dynamic environment of high temperature and high pressure, the PCB is immersed in the lead-tin solder (melted), and the air knife will flatten the liquid solder on the copper surface)
The HASL process is relatively dirty, smells bad, and is relatively dangerous, and the technical control is relatively complicated. If the flatness is not good, it will affect the welding quality of the components. With the advancement of technology, a HASL process suitable for assembling QFP and BGA with a smaller pitch has also emerged. In actual applications, OSP and ENIG are both selected. At present, in PCB surface treatment, 20% -40% will use hot air leveling, let us understand its advantages and disadvantages together.
(1). Function:
The lead-tin solder (melted) forms a layer of anti-copper oxidation coating, slows the oxidation of copper, and forms a copper-tin metal compound (about 1 to 2 mils in thickness) at the junction with copper, providing good solder-ability.
(2). Advantages and disadvantages of hot air leveling:
Advantage:
a) Low cost, good solder-ability
b) Fully cover the side edge of the wire
c) Avoid corrosion disconnection on the printed board
(3).Disadvantages:
a) Poor surface flatness
b) The tin beads produced are easy to short-circuit the components of the fine-gap pins
c) The PCB is prone to warp due to large thermal shock.
(4). General process:
Micro-etching→preheating→coating flux→spraying tin→cleaning.
Tin spray is divided into lead-free spray tin (lead content less than 0.1) and lead spray tin (lead content 37%), the difference between them:

Lead-free

Lead

Cost

low

lower(relative to lead-free)

Mechanical strength

medium

High (relative to lead-free)

Brightness

dim

bright (relative to lead-free)

RoHS

can pass

Cant pass

Subscribe for our newsletter

Please read on, stay posted, subscribe, and we welcome you to tell us what you think.

click here to leave a message

Leave A Message
If you are interested in electronic products and want to know more details, please leave a message here,we will reply you as soon as we can.

Home

Products

about

contact