Heat sinks in electronic packaging can be flame sprayed with dielectric coatings of alumina or beryllia and finished off with an organic sealer to provide high heat and electrical resistivity

Mackay, T. L.

Muller, A. N.

Vanaman, J. B.

English

NASA Technical Reports Server

December 1967	 .	 -	 Brief 67-10534 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Flame Sprayed Dielectric Coatings Improve Heat Dissipation in 
Electronic Packaging 
The problem: 
Present electronic packaging applications require 
the transfer and dissipation of heat , from heat-
generating components while maintaining the com-
ponents electrically isolated. The usual approach is 
to mount the components to an aluminum heat sink 
which has been coated with an electrically insulating 
material. The use of an anodized (aluminum oxide) 
coating has been found to be inadequate because of 
its low electrical resistance when exposed to a high 
humidity environment. 
The solution: 
Flame spray the heat sinks with coatings of alumina 
(Al203) or beryllia (BeO) and then finish off with an 
organic sealer. 
How it's done: 
Beryllia (BeO), and alumina (Al203) were examined 
for possible application as heat sink coatings. Mag-
nesia was eliminated from consideration because it 
was found to be very hygroscopic. The materials ap-
plied to aluminum test panels for examination were 
high purity 325 mesh alumina and 200 mesh beryllium 
oxide. A controlled atmosphere chamber was used for 
the flame spraying of beryllia since it is a toxic mate-
rial. 
After the oxide coatings were flame sprayed onto 
the test panels, organic heat sealers were brushed on 
the coatings to inhibit moisture from penetrating into 
the pores of the coating. Three seaters were tested: 
an epoxy resin, an insulating varnish, and a phenolic
sealer. The coatings exhibited the best shock re-
sistance with the epoxy resin sealer. 
Notes: 
1. Flame sprayed alumina and beryllia coatings with 
an organic sealer brushed over them can be used 
from room temperature to 400°F. They have elec-
trical resistivities of approximately 105 ohm-cm 
at room temperature to 1012 ohm-cm at 400°F 
with no dielectric breakdown at 500 volts. The 
thermal conductivity of alumina is about one-sixth 
of that for beryllia. Both coatings (with the epoxy 
sealer) withstood a thermal cycle test from 400° F 
to —85 0 F with a transition period of approximately 
three minutes. 
2. Inquiries concerning this invention may be di-
rected to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B67-10534 
Patent status: 
Inquiries about obtaining rights for the commer-
cial use of this invention may be made to NASA, 
Code GP, Washington, D.C. 20546. 
Source: T. L. Mackay, J. B. Vanaman, 
and A. N. Muller 
of Douglas Aircraft Co.
under contract to 
Marshall Space Flight Center 
(M FS- 13569) 
Category 01 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19670000533 2020-03-11T21:00:19+00:00Z


Flame sprayed dielectric coatings improve heat dissipation in electronic packaging

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