Making lightweight design possible with surface treatment technology

Saving weight and costs with solderable aluminium

Challenge
Copper had been used to make a sheet metal component for a brake control system in the automotive sector. The cooling plate in the brake control system serves to conduct heat from a processor. In this case, the reasons for replacing the copper part with aluminium were obvious, as firstly aluminium is three times lighter than copper, which saves around 66% in weight, and secondly, aluminium is far cheaper than copper. The challenge was to coat the aluminium with a layer that enabled the processor to be sufficiently firmly bonded with the plate to dissipate the required amount of heat.

Solution with added value
In order to conduct the heat from the processors and firmly bond the heat dissipation plate to the processor, the base material (copper) first needed to be tin-plated beforehand. In order to create a firm bond between the processor and the aluminium, the material was electrolessly nickel-plated and then soldered. What sounds so simple here is the result of sustained customer-oriented development on the part of the Holzapfel Group, which worked intensively on the project for two years before the series production start-up.

In order to meet the specifications of the plate and achieve the required heat dissipation capability, we developed a special electroless nickel process to ensure solderability. It was particularly challenging to align the solder points in such a way to ensure they were always reliably coated during the process. This was only possible by developing a special rack technology to convey the components upright through the coating facility. At the same time, special attention had to be paid to achieve sufficient density on the specially designed rack – i.e. as many components as possible per plating process – to make the procedure even more economical. Apart from cutting material costs for the plate by using aluminium instead of copper, the coating process was also made more efficient.

Moreover, in collaboration with the customer, the Holzapfel Group has developed a solderability test performed during production to ensure the quality of the coating. Furthermore, the special coating process prepares the component for the next processing step in such a way that it can be soldered with a special soldering paste without needing to be cleaned before or afterwards.

Value stream optimisation a further advantage
The Holzapfel Group's automotive industry customer also benefits from the value stream optimisation that was carried out during the project phase, as the rack technology was adapted to suit the existing customer cassettes. After the coating process, the components are transferred from the coating cassette to the customer cassettes in the correct position. The customer can then automatically remove the plates from the packaging via robot and feed them into the assembly process. For two components that are coated with solderable electroless nickel in quantities of millions, this is also a relevant aspect in terms of economy.

Technical details and advantages of solderable electroless nickel plating:

• Solderable
• Functional surface for protection against corrosion and wear
• Dimensionally stable coating
• High chemical resistance
• Excellent abrasion resistance
• Layer structure free of lead and cadmium

Interesting for:

• Automotive applications
• Electronic control and regulation devices
• Electrical industry, e.g. for cooling elements (stamped heat sinks, die-cast heat sinks), housings for control systems, power electronics devices
• Microelectronics
• Mechanical engineering
• Systems engineering
• Medical industry / medical devices
• Precision mechanics / optical goods industry
• Aerospace industry