Lead-free hot air leveling for rigid flex PCB：

Application: Replace SnPb HASL.

Cost: medium to high.

Compatibility with lead-free: compatible.

Storage period: 12 months.

Solderability (wettability): high.

Disadvantages:

* Not suitable for devices with pin center distance <0.5mm, because bridging is prone to occur.

* Not suitable for places with high coplanarity requirements, such as BGAs with medium and high pin counts because of HASL* * Process plating thickness changes relatively large, and the coplanarity between pads and pads is poor.

* Due to the relatively large thickness of the plating layer, the hole diameter (DHS) must be compensated to obtain the desired finished metalized hole diameter (FHS), typically FHS=DHS-4~6mil.

* Due to the high peak temperature of the surface treatment, thermally stable dielectric materials must be used.

Supplier resources: Currently limited, but with the development of using lead-free processes, it will be more and more.