Final surfaces of flex and rigid-flex circuit boards

The following solder surfaces are available for the use of 3D technology

Immersion Tin*

    • Surface HAL is possible for rigid-flex, but is not compliant with RoHS (German Electrical and Electronic Equipment Act). Surface HAL is not possible for flex and FR4 rigid-flex (semiflex)!  
    • Lead-free HAL is not approved for 3D technology. The high process temperatures and the moisture sensitivity of polyimide render this surface treatment impossible. Furthermore unfavourable layer thickness distribution (1 to 40 µm) is very disadvantageous for fine pitch components.  

    • * Immersion tin (chem. Sn): Rigid-flex circuit boards with polyimide have to be dried prior to the soldering process. The lead-free soldering process with elevated temperatures makes the drying process all the more crucial in minimising the risk of delamination. Read our drying recommendations in this regard!

    Solder surfaces age prematurely due to heat exposure during drying. This can have a negative impact on soldering performance in particular with immersion tin. The aggressive process chemistry of the coating process with immersion tin also places the material under considerable stress and may damage the solder-mask lacquer system in particular (infiltration).