Tool design and press selection by ECL's engineering staff ensure optimal pressing efficiency. The mass-volume relationship of these compacted contacts is a key element of the quality of sintered contacts. Consequently, this process is closely monitored and subjected to statistical controls. Rotary presses, single die mechanical presses and hydraulic presses are all used to ensure appropriate densities are achieved for the wide range of contacts ECL supplies. The essential steps involved in the production of discrete sintered contacts through unit compaction powder metallurgy are compaction, sintering, infiltration, and solder flushing.
The sintering process is an essential step in the production of unit compaction sintered discrete contacts. High temperature heating of the compacted contacts fuses the constituent materials as they are "wetted" together. The furnace temperature, atmosphere, and the time that contacts are in the furnace are all key elements of this process that are closely monitored at all times.
Infiltration is a process in which the pores inside a sintered contact are filled with either molten silver or copper, often referred to as the infiltrant. Infiltrating is performed through high temperature heating of the sintered contact and the infiltrant in furnaces which have a reducing atmosphere. Aside from the furnace atmosphere, temperature and process times are critical elements of the infiltration process. As such, these parameters are closely monitored throughout the infiltration process. Depending on the final application, infiltrated contacts are supplied with or without serrated backs. The serrations provide a surface that captures the excess infiltrant and is also well suited to the resistance brazing process. Where high currents are involved, the surfaces to be brazed are typically machined flat prior to solder flushing.
Brazing alloys, commonly called solders, are often required to attach discrete contacts to their supports when creating contact assemblies. In many cases, the braze alloy is applied prior to the delivery of the contact for its subsequent braze attachment. Contacts are solder flushed whether they are wrought or sintered and whether they have serrated backs or machined surfaces. Typically, contacts are placed on a pre-cut shim of the required braze alloy and these two components are then passed through a high temperature furnace. The furnace temperature and the length of time in heat allows for the solder to adhere to the contact's brazing surface. Furnace atmosphere is also an important feature of this process.
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