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From [log in to unmask] Sat Apr 27 15: |
27:18 1996 |
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"Davis, Phil" <[log in to unmask]> Wrote:
| Phil Davis
| Manager Mechanical Engineering & Packaging
| Wilcox Electric, Inc
|
| We are looking at eliminatingng the gold plating on
| some large (18" x 24")
| microstrip boards by having the supplier coat the
| boards with ENTEK. These
| microstrips are on Teflon (GXN) substrate.
|
| 1) Does anyone have experience using ENTEK on Teflon
| sunstrate?
Generally GXN Teflon is used where electrical signals are of
primary concern. In most cases (95% +) the traces on Teflon
boards are not covered by soldermask because of the electrical
performance desired. There are however some Teflon boards that
cover the traces with soldermask (embedded microstrip).
If your Teflon board has soldermask over the traces, you should
have no problem using ENTEK in IR reflow. Assuming that the
assembly process has been set up for ENTEK coated boards.
If your board doesn't have the traces covered with soldermask,
then it depends on if you want exposed copper traces. ENTEK is a
temporary coating that has a 12 month shelf life in preserving the
copper for solderability. The traces of the board will be
protected from the environment by the ENTEK. It would depend on
the environment where the board will be used and whether or not
you sit in the camp that believes exposed copper on finished
boards is OK. I think the jury is still out on exposed copper.
I have limited data supporting either side (exposed copper is OK
vs exposed copper is detrimental). I am sure that there are
applications where each is justified. I welcome others to comment
on this issue.
|
| 2) Can we IR reflow the components to the board while
| using ENTEK? Do we
| need to remove the ENTEK before assembly?
ENTEK is a thin organic coating that is intended to protect the
surface of the copper until the assembly, generally it is called
OSP (organic solderability preservative) ENTEK being a trade name.
The flux used in assembly attacks the surface of OSP allowing the
solder to bond directly to the copper surface.
As a board manufacturer, we are only aware of 1 customer out of
many using ENTEK that had problems with IR reflow on an OSP
surface. The solder paste used had an antislump agent in it that
inhibited the flux from attacking the OSP. After changing the
paste, there were no problems.
Using OSP in wave solder assembly may need process adjustments to
allow the board sufficient time to remain in contact with the flux
to remove the OSP. ENTEK has been used successfully in many
assembly houses using wave solder as an assembly method.
I can give you a couple of contacts if you need more information
as well as a couple of reports regarding ENTEK.
Darren Hitchcock
Merix Corporation
Forest Grove, Oregon
[log in to unmask]
(503)359-2658
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