Bev , from my blooming days on OAK switches (yes; I know 'm ancient) pole configurations on wireless works : I remember (still; is that good or bad?) your problem : We've had two actually : 1 the intermittence you talk about we fixed by "tweezers" wiper pinching the board in between . That is if you can go that way . If you can not, and have space on tip (should have) split the arm as well (one tip will always touch) . Or if you have space on disk ; take the wiper from radius to dia with two opposite contacts ; bearings preferred this wing tips solution most as well (instead of side stress on radius only ; just a flat bearing held by the wing pressure . 2 The pressure X smear X SIR X ? ; you easily and fast determine on life test with rev counter ; will take ol' fox like you couple hours most : just sacrifice one of the assemblies for tensioning screw mod = play with pressures ; I would not recommend any "guidelines" ; from bitter experiences I found even changing fab's played a role on the same specs . 40um should do . On the disc design side : no mask in between ; OR we went on SIR grounds even to extremes of routing ovals in between (it was much harder on contacts [very much hand edges treatment] keep the pads 1mm from edge) ; or shallow triple grooves radiating from centre . That took care of smears ; the contact tip can be fairly robust . Most of that was mil. work with progress inspections ; you have to transpose the cost conditions . see you Bev paul > ---------- > From: Bev Christian[SMTP:[log in to unmask]] > Sent: Friday, 12 February 1999 4:23 > To: [log in to unmask] > Subject: [TN] Contact Force/Pressure > > TechNetters, > This came from one of my lab customers. Any info you can give me to pass > along? Thanks > Bev Christian > Nortel Networks > > We have a design for an "encoder gear" assembly, it is essentially a gear > with some contact fingers (aka wiper arm) staked onto the gear. The wiper > arm is made from one solid piece. Once in the final assembly the gear is > driven by an outside motor, the wiper arm fingers are in contact with > traces on a PCB. As the gear is rotated the wiper arm will result in > various outputs as the traces are shorted to the inner ground connection. > There are four outputs, one ground and three position outputs. Each of > the > four finger tips is bifurcated. The traces on the circuit board are gold > plated with an approximate thickness of 40 microns, under the gold the is > a > nickel/ cobalt plating. > > We have been experiencing great heartache due to intermittence as the > wiper > arm is rotated. The intermittencies cause false outputs which cause our > tester to fail modules. We have done many experiments to ensure that the > PCB traces are sufficiently clean. We know must look at the system > design. > > The information I am seeking is whether there are specifications or > guidelines for the necessary or recommended contact pressure between the > wiper fingers and the PCB traces to ensure reliable continuity. I have > looked through the IPC manuals we have and found nothing. > > I would imagine that this type of information would apply to potentiometer > and very low current switch manufacturing. > > I would be very grateful if you knew of any information on this subject or > knew where I should look. > > ################################################################ > TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c > ################################################################ > To subscribe/unsubscribe, send a message to [log in to unmask] with > following text in the body: > To subscribe: SUBSCRIBE TechNet <your full name> > To unsubscribe: SIGNOFF TechNet > ################################################################ > Please visit IPC's web site (http://www.ipc.org) "On-Line Services" > section for additional information. > For technical support contact Hugo Scaramuzza at [log in to unmask] or > 847-509-9700 ext.312 > ################################################################ > ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################