Some HASLs are configured at a ninety-degree angle to allow for complete immersion of the board in the solder bath, resulting in high-quality finishes. Once the solder becomes solid, the boards are passed through a washer to remove any flux residue. Hot air knives are then used to remove any excess solder, with the air knife modules adjusted to the melting temperature of the solder. There are three steps involved in applying HASL finish on a PCB board: cleaning, fluxing, and spraying melted solder to achieve the required wetting. It is not suitable for fine-pitch components, and a leveler may be required to increase their flatness.HASL is a great choice for wire binding.High-temperature processing can damage plated through holes, and plated hole tolerances can be difficult to handle.The soldering process can lead to non-wetting or dewetting when the solder coating does not fully form the intermetallic layer.The hot air soldering process involves irregular surfaces, making it unsuitable for Montagem SMT.HASL finish thickness can be made uniform by controlling the amount of solder present on the pad after hot knife and thermal tension.
HASL has a longer processing window, allowing for quick manufacturing schedules without requiring a large number of boards.Boards with HASL can operate at temperatures up to 265 degrees Celsius.It can be easily applied to the board without requiring specific equipment.Materials used for this finish are inexpensive and readily available.
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