HAL Surface

During the manufacture of printed circuit boards, the copper of the pads needs to be protected against oxidization during storage and subsequent processing. One possible method is the tinning of the copper surfaces. In the HAL (Hot Air Leveling) process, boards are first completely submerged in a flux tank, followed by submerging in liquid solder. Excess solder is removed through blasts of hot air during the withdrawal from the solder tank. HAL surfaces offer the best solderability of all surface treatment methods. One major drawback is the lack of co-planarity, which is the result of the excess solder being blown of the board. For this reason, HAL surfaces are not suitable for fine-pitch SMD applications.