Repairing traces on a PTFE board is generally not done.  The 
reason the designer is using the PTFE material is strictly for 
the electrical performance.  (it certainly isn't price)

Rebonding the traces increases the dielectric spacing as well 
as change the effective dielectric constant.  The higher 
the frequency, the more impact the dielectric immediately 
under the conductor will have.  Both of these changes will 
affect the electrical performance to some degree. The thinner 
the base laminate, the larger the impact.  Also the amount of 
adhesive put under the trace during the repair is technician 
dependent and will affect the variation of electrical impact.

If the repair is in a location where the electrical impact
isn't a concern,  the PTFE will need to be prepared before
receiving the adhesive.  Usually a TetraEtch or Plasma Etch
is used to prepare the surface for bonding.  In any case, I 
would ask the circuit designer before performing any conductor 
rework.  If the rework is approved, minimize the amount of 
adhesive under the conductor.

Darren Hitchcock
Merix Corporation
[log in to unmask]



"ddhillma" <[log in to unmask]> Wrote:
| 
|      Ted-
|      
|      We do repair on PTFE boards on occasion - I 
| don't know what adhesive 
|      we use but we do use TetraEtch from W.L. Gore 
| to prepare the bonding 
|      surface. TetraEtch contains HF acid which is 
| no fun to use but the 
|      resulting bonding surface is very robust.
|      
|      
|      
|      Dave Hillman
|      Rockwell Collins
|      [log in to unmask]
|      
| 
| 
| ______________________________ Reply Separator 
| _________________________________
| Subject: ASSY: Teflon Board Repair
| Author:  [log in to unmask] at ccmgw1
| Date:    5/8/96 1:30 PM
| 
| 
|      
|      Occasionally with Teflon base material boards 
| adhesion of a pad or run 
| is lost during assembly, especially with 
| connectors and larger parts which 
| require more heat,  and we are wondering if anyone 
| has experience in rework 
| or repair to reattach pads or runs to Teflon 
| boards.  We would like bond 
| strength in the range of original and without 
| microwave performance 
| degradation.  Anybody got any ideas or suggestions?
|      Thanks
|           [log in to unmask]
|      
|