Thermal spray deposits are used extensively in the electrical industry
for a number of applications including electrically conductive coatings
and resistance type heating circuits.
Condensers, Resistors, and Brushes:
One application is the production of electrolytic condensers.
Automatic wire flame spray equipment is used to apply aluminum onto a gauze-like
fabric. Special air caps are employed to provide uniform spray patterns at
high velocities. Carbon and ceramic resistors and carbon brushes are sprayed
with a thin film of copper to provide an electrical connection of high conductivity.
Pigtails may be soldered to the copper layers on the carbon brushes.
Ceramic resistors are also coated.
Surface preparation is unnecessary, because the copper particles readily
adhere to the relatively porous surface of the carbon or ceramic parts.
Circuits, Panels, and Switches:
Thermal spraying is a useful method of producing thick film electrical circuits.
These circuits can carry higher currents than the printed type, yet are more
flexible than stampings.
Circuits are produced by spraying the metal onto a nonconductive substrate
- usually plastic, ceramic, or glass. The bond to plastics is obtained by grit
blasting the surface. Unglazed ceramics are sprayed without surface preparation.
The circuit patterns are produced by spraying through masks and etching away
unwanted material afterward, or by molding the patterns into the plastic. After
the entire surface has been coated, the molded circuits are revealed by grinding
away the excess coating to the plastic substrate. The most commonly used metals
for thick film applications are copper, aluminum, zinc, and silver. Materials
which may make thermal spraying even more attractive to the electrical industry
are being developed for stable resistors, capacitors, and inductors. Heater
panels have been produced by spraying onto thermally treated glass. Aluminum
is the preferred metal for use on glass. Silver is used in the contact areas
of large knife switches to provide good electrical contact.
Shielding material is used to eliminate electromagnetic and radio frequency
interference (EMI/RFI) and to dissipate static discharge sparks. Applications
include computer terminals, electronic office equipment, medical monitoring
devices, and sensitive electronic equipment. Housings constructed of temperature
sensitive plastics do not offer shielding. Zinc coatings provide protection,
are inexpensive, and are easily applied. Adhesion is excellent, as is electrical
conductivity, which provides high levels of attenuation in the range of 60-120
In electronic applications that require wear resistance with a high dielectic
factor, pure aluminum oxide is applied by wire flame spraying.
For more information go to:
Thermal Spray Association