Ellen Berkman asked:
>1. In order to strengthen a wire wrap connection, is it permissible
> to solder the post? Where would I find this in IPC?
Yes, although soldering may not mean "stronger".
I don't know of an IPC reference, but the Bell System Practices section
800-612-154 specifically talks about a requirement to solder "solderless
wrapped connections" (Wire-wrap is a trademarked name of Cooper Industries)
when the materials don't meet a materials requirement. Wrapped connections
are not to be made _over_ soldered surfaces, according to the same
specification.
>2. Is it permissible to wire wrap uninsulated wires to posts .1 inch
> apart?
This is a loaded question. You imply that some ultimate authority would be
involved. You don't tell us about current or Voltage, whether this is a
heart-lung machine or a video game, etc.- but it is common practice to do
so even with uninsulated wires. The header posts are typically
uninsulated...
I have an ancient copy of a copy of Bell Labs X-17151 Issue 9 "Solderless
Wire Wrap Terminal Design Information" which recommends a minimum terminal
spacing based on the wire size. For 28 and 30 AWG, they recommend 0.100 -
0.125", and for 26 AWG, 0.115 - 0.175".
There is an EIA std. RS-280-B, and a mil-std 1130-B related to wrapped
connections. I'm unfamiliar with these.
There is a type of wrapped connection referred to as "modified" in which
the first 1-2 turns (at the base) are made with the insulated section of
the wire. Modified solderless wrapped connections are reported to be more
stable in high vibration situations.
>3. We have dual row Molex headers (pin spacing is .1 in apart).
> We want to have the ability to jumper to opposite pins. Does
> someone have a recommendation on how to make the jumper block
> ruggedized yet flexible (so that jumper selection can be changed
> at a later time)? Note: The Molex pins have a smaller cross
> section than standard wire wrap.
The wrapped connection is likely to be more stable than a removeable shunt
on a pair of male header posts. I'm assuming you refer to 0.025" square
header posts on 0.100" centers. Unless you are referring to an extreme
environment such as airborne, a shunt with gold plated contacts on a gold
plated post is quite stable.
The cross-sectional area of the "contact patch" formed when the wire is
stretched around the sharp corner post is more than the cross section of
the wire when about 7 turns are used. The AT&T spec asks for 9 turns of 26
AWG wire on an 0.025" square post., and 7 turns with 28 or 30 AWG, using
OFHC copper (apparently the smaller the wire, the fewer corners req'd).
They require a modified wrap with 28 or 30 AWG.
I suggest you assure yourself that you are using the apppropriate type of
drawn wire posts with sharp corner radii, and that the materials and finish
of the wire and the post are designed for wrapped connections. The wire
should be annealed. Wrapped connections have a good reliability reputation,
but they are not exactly modern technology in 1997.
Cooper Tools can probably provide you with more guidance, they are probably
the leading supplier of solderless wrapping tools and supplies.
CooperTools
P.O. Box 728
Apex, NC 27502-0728
919-362-7542
See http://www.coopertools.com/pages/wirewrap.html
regards,
Jerry Cupples
Interphase Corporation
Dallas, TX USA
http://www.iphase.com/
##############################################################
TechNet Mail List 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 web site (http://www.ipc.org/html/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
##############################################################
|
