HAL vs. immersion gold

The ability of HAL (Hot Air Levelling) circuit board surfaces to fulfil future requirements (such as increased part densities, reduced spacing between pins, etc.) continues to decrease.

This is because the HAL process creates the surface of the circuit board with a tin bath. The fluid tin forms "drops" on the surface areas and runs along the edged of holes and pads. This causes the surface of the circuit board to be very thin right at the edges, and may lead to solder problems.

A uniform surface thickness cannot be achieved with HAL.

Example of a HAL surface

Example of a HAL surface

The tin surface in the HAL process is very thin right at the edges, and may lead to oxidation or solder problems. A good solderability can be guaranteed only in the middle of the "drop".

Example of an immersion gold surface

Example of an immersion gold surface

The tin surface in the HAL process is very thin right at the edges, and may lead to oxidation or solder problems. A good solderability can be guaranteed only in the middle of the "drop".