The chemical physical bonding between the materials can be metal-to-metal or insulator-to-metal. This connection must be robust, resistant to high temperatures, and compatible with vacuum conditions.
When subjected to vacuum or elevated temperatures, the presence of flux on an electronic component can lead to detrimental effects. The flux, which comprises acids and salts, transitions to a gaseous state due to its high vapor pressure. The subsequent condensation of flux material on insulators can create conductive pathways, resulting in leakage currents that may compromise the integrity of the costly component. Regrettably, the most active (and thus corrosive) fluxes tend to establish the most robust connections. Certain material attributes, such as vacuum resistance, are unattainable under standard atmospheric manufacturing conditions. Additionally, a notable issue with conventional atmospheres is the inevitable incorporation of gas impurities into the connection surface.
The resolution to this issue lies in employing high vacuum soldering and brazing techniques. In both methods, the bond between the two disparate materials is established through a third metallic substance, known as the solder or brazing filler material. The key difference between soldering and brazing is that soldering involves reversible adhesion, primarily, while brazing leads to the irreversible diffusion of the materials, resulting in a significantly stronger bond. The entire procedure is conducted in either a high-vacuum (HV) or an ultra-high vacuum (UHV) setting. Such environments eliminate the risk of oxidation and permit the use of flux-free solder materials.
