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16
Appendix F
Concerning Conformal Coatings
LM104−P50−
1
J
P
3
T
E
R
M
.
J
P
4
J
P
5
1
2
2
3
3
4
456
S
E
R
V
I
C
E
R
E
S
E
T
J
P
2
J
P
1
P3
R11
Certain applications require a conformal coating be applied to the board for additional
environmental protection. There are several “keep-out” areas on the LM104-P50 board that should
be masked prior to coating:
• PC/104 connectors P1 and P2
• Jumpers JP1, JP2, JP3, JP4 and JP5
• Network connection P3
• The 27C256 EPROM (U2) and its socket
• The PEEL (U4) and the PAL (U6) and their sockets
• The area highlighted in the above diagram (Options 1/2/3/6 only)
The last item is very important. Echelon requires that all network transceivers be protected against
electrostatic discharge (ESD). VISTA Electronics has incorporated several features to ensure this,
including spark gaps for high voltage transients. These spark gaps are part of the printed circuitry
near the network connection P3. If a conformal coating covers the gaps, they will not function
correctly. To maintain proper protection, keep any coating at least 0.25” (6.3mm) away from the
exposed (shiny, tin-plated) portion of the spark gaps (Options 1/2/3/6 ONLY).