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Evaporation and sputtering: Substrate heating dependence on deposition rate.

01 January 1989

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The deposition of copper into the through-holes and vias of printed wiring boards (PWBs) has been done using vacuum processing techniques frequently referred to as "dry metallization". Two vacuum processing techniques are evaporation (or physical vapor deposition, PVD) and sputtering. Both techniques are used routinely in industries other than the PWB industry. One of the most important limiting factors for any deposition process is the substrate heating. The temperature of epoxy-glass PWBs should not exceed 180C (350F). There are several contributions to substrate heating: radiation, kinetic energy of incident particles (atoms, electrons, ions) and the heat of condensation (sublimation). For evaporation, there is one major contribution, the heat of condensation. Sputter deposition has two main sources of substrate heating, the heat of condensation and the kinetic energy of the incident atoms. Experimental data for the absorbed incident power versus deposition rate are shown for both evaporation and sputtering systems. The experimental apparatus used to measure the power absorbed by a PWB substrate is described.