Base materials and their specific parameters.
b) in case of a finished PCB: on an etched spot, whereby the solder stop mask must be deducted and added to the nominal thickness of the Cu-foil.
Prerequisite: The conductive pattern is identical on both sides.
For the various fields of applications, we generally use halogen-free solder resists. Our classic standard coating is the green XV501 HF produced by the company “Coates” which is casted on the PCB. In case of other coatings and colours we use a silk-screen printing method.
The choice of the material of the surface finish depends on the PCB layout, on the number of soldering points and on the holding times between the individual soldering processes.
HAL lead-free is not suitable for all layouts, as it not as planar as e.g. HAL with lead. In addition it is more difficult to cover pad surfaces on a large scale with it and it may lead to defective spots.
Galvanic gold with HAL lead-free is currently not possible.
The width and length of the connection surface depends on the diameter of the wire which is used. For each individual wire, the minimum width of the pad should have the triple wire diameter, and the minimum length should have the six fold wire diameter.
The bond surface consists of chemical Ni 4 – 9 µm and chemical Au 0.1 ± 0.05 µm. The phosphorus concentration in the nickel is ≤ 10%.
The finish roughness is Rz ≤ 3 µm Rt ≤ 4 µm Ra ≤ 0.5 µm. Bond boards are never delivered without intermediate paper layers.