Technical Information
HAL lead-free
Soldering pad cross-section
| Topography | convex |
| Layer thickness | approx. 1-30 µ *1 |
| Surface corrosion | not critical |
| Diffusion zone growth | not critical *3 |
| Solderability 1st soldering process | good |
| Under O2 long term | good |
| Under O2 short term | good |
| Under N2 long term | good |
| Unter N2 short term | good |
| Edge connectors | not suitable |
| Press-Fit technology | limited suitability |
| Aluminum wire bonding | not suitable |
| Keyboard applications | not suitable |
| Special advantages | Robust soldering surface with solder depot, good shelf life |
| Special disadvantages | Lack of surface planarity, thus critical for BGA and similar pads, HAL causes high thermal stress |
| Richter Elektronik can recommend the following solutions: (Based on current knowledge, without obligation) |
For all PCBs where lack of surface planarity does not cause problems and the thermal stress caused by HAL is not critical. |
1*
Physically deposited layers, e.g. HAL layers deposited by the application of liquid solder, have a significantly higher thickness, however, they are not plane.
3*
Independent of the deposition method, generally a so-called diffusion layer is formed between two layers of different metals. This barrier layer is created by an exchange of atoms between the metals of different nobility. There will be a “mixing” of the base copper and the metal of the “ennobled” soldering surface. The thickness of this diffusion layer depends on the type of metals involved as well as on the temperature conditions and the time for which the temperature conditions affect the layer system. Higher temperatures and longer residence times lead to a growth of the diffusion layer (e.g. during storage and soldering).
4*
The following can be derived from the items 1 to 3:
Electroless deposited layers are plane but very limited in thickness. This results in a high danger of loss of solderability as the diffusion layer may penetrate the entire thickness of the coating under certain circumstances in which case the plane surface “ennobled” for soldering is not solderable any longer. On the other hand, a physically deposited soldering surface has a much higher thickness which under normal circumstances is several times thicker than even a seriously grown diffusion layer. However, it is to be considered that this coating has the disadvantage of a lacking planarity.