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Ormecon Chemical Tin as an HAL ( Hot air levelling ) alternative

The ever increasing density of SMD pins means a better surface finish is required. HAL does not offer the required finish any longer. The HAL process see the boards being "dipped" vertically into molten tin, upon its exit it is blown with hot air. This leads to drops and puddles on the pads.

Beta LAYOUT now offers an alternative lead free finish - Chemical Tin.

The tinning is as with HAL is a partial covering and has nothing to do with the old method of Lead / tin reflow.

Due to the smooth surface finish assembly of fine pitch is considerably easier.

The circuit board is not put under the same temperature stress as with the HAL process and as such does not suffer from warping or bending.

The chemical tin surface allows for multiple soldering and also shows great results with press-fit technology.

The soldering parameters are on par with those of a HAL surface finish.

For prototypes not necessarily critical but still of interest:

The solderability of a PCB with a Chemical Tin finish is about 6-12 months.

Background :
Between the copper pads and the Tin layer there is a so called intermetallic phase. On delivery this is about 0.25um thick. While in stock, the copper continues to difuse the tin layer so that the thickness of both copper and tin continues to abate. Should the copper reach the surface it would oxidise and the solderability of the material would be impared. Therefore the shelf life of Chemical Tin finished boards should be slightly shorter than that of a HAL finished pcb.

Properties of Chemical Tin.
Layer thickness : 0.8-1.2 um
Solder paramater : Similar to HAL or Chem NI/AU
Soldering types : All variations possible
Solderable :- 2-3 times
Pressfit : Yes
Bondable : No.