Meaning
Metallic laminates of disparate thermal and mechanical properties represent a standard approach for optimizing electrical pathways in high-current power distribution assemblies. An aluminum copper stackup combines the low weight of aluminum with the superior conductivity of copper in terminal blocks or busbar assemblies. The joint requires careful control to prevent thermal-cycling failures and degradation.
Galvanic Degradation
Electrochemical reactions occur when moisture enters the junction between the two different metals. This galvanic activity accelerates the oxidation of the aluminum copper stackup, leading to an increase in contact resistance over time. To isolate the joint from environmental moisture, designers apply protective platings like tin or nickel to the interface.
Thermal Expansion
Mismatched expansion coefficients cause sliding movements at the interface during thermal cycles of high-power operations. When the system powers up, the aluminum expands faster than the copper, creating localized stresses in the aluminum copper stackup that can yield the softer metal and lead to micro-fretting. This plastic deformation leaves a physical gap when the joint cools down to ambient temperature, which permanently degrades the electrical connection.
Using hard metal inserts can mitigate this differential displacement and protect the assembly.
Clamp Retention
Sustained electrical contact depends on maintaining high pressure over the service life of the connection. Spring-loaded fasteners counteract the creep behavior of aluminum in the aluminum copper stackup to keep the interface under constant compression. Standard practice dictates the use of Belleville washers to absorb the differential expansion without loosening.
