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'[EE] Socket security'
2004\10\21@195007 by Dave King

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I have a board that I used a 8 pin socket for the pic 508. In use they will be
exposed to a bit of vibration so I have some concerns about securing the cpu.

I know the easiest thing is simply to solder the pic direct to the board
but I need
the option of easy access/removal until everything is stabilized. It's
close to that
point where I am comfortable about the code but for a few that I want to
let out
now with a socket I am wondering if there is a way to nail the pic in place.

Adhesives?  Anything like a blob of silicone to hold it in place? Something
that is non conductive and non corrosive?  I think good ole rtv silicone
will corrode the pins. I'm not up to date on all the wonder goo's out there.

Solder strap or wire across the pic?

What else is there to try?  It needs to be able to allow some limited rework.
ie pop the pic out and reprogram and reinsert so a thick conformal coating
would be more trouble than its worth as an example.

As far as the replacement bit I doubt it will need to be done more than once
for these few boards but I need to keep the option open.

any ideas?

Thanks

DaVe

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2004\10\21@200534 by Brent Brown

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On 21 Oct 2004 at 16:49, Dave King wrote:

>
> I have a board that I used a 8 pin socket for the pic 508. In use they will be
> exposed to a bit of vibration so I have some concerns about securing the cpu.

Nylon cable tie works very well if there is room for it to go underneath the
socket. I think the turned/machined pin sockets are good for this.

--
Brent Brown, Electronic Design Solutions
16 English Street, Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile/txt: 025 334 069
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2004\10\21@200643 by Marcel Duchamp

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1. Silicone RTV. I used it for years on socketed EPROM's in a portable
instrument.  Occasionally they needed updates when in the shop for repairs
and I never saw the slightest corrosion from the RTV.  However, I never
applied the RTV to the pins.  A tiny dab at each end of the chip to the
socket was sufficient.

2. Nylon penny ties (cable ties, ny-ties, etc.) could be used if they fit
under the socket or through pcb holes if there are any suitable.

3. PIC12F508 w/ICSP. No socket.
MD

At 04:49 PM 10/21/04, you wrote:

>I have a board that I used a 8 pin socket for the pic 508. In use they will be
>exposed to a bit of vibration so I have some concerns about securing the cpu.

____________________________________________

2004\10\21@201024 by CSB

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>
> What else is there to try?  It needs to be able to allow some limited
> rework.
How about a blob of hot glue? Not sure if it corrodes/eats anything, but wouldn't be too hard to remove (maybe not enough?).

Maybe not a few strips of duct tape...

Christian


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2004\10\21@202012 by Josh Koffman

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Hi Dave,

Haven't seen you post in awhile. How's that ZIF socket I sent you working out?

Ok, back to your question. At work we use a little dab of silicone on
a lot of our screws and stuff, just to be sure they won't work loose.
Works great, and it isn't too hard to get off if you really need to.
If you get a non corrosive silicone (without acetic acid) then you
should be ok. Another option might be a stiff wire jumper that goes
over the PIC and gets soldered down to the board.

Josh
--
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completely foolproof is to underestimate the ingenuity of complete
fools.
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On Thu, 21 Oct 2004 16:49:15 -0700, Dave King <.....kingdwsKILLspamspam@spam@shaw.ca> wrote:
{Quote hidden}

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2004\10\21@204943 by Christian A. Weagle

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Someone makes DIP sockets (just saw them in Jameco I believe) that have
locking tabs on hinges on the ends, similar to certain pcb-mount IDC
headers used in automotive apps (for example).

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2004\10\21@210755 by Dwayne Reid

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At 05:49 PM 10/21/2004, Dave King wrote:

>I have a board that I used a 8 pin socket for the pic 508. In use they will be
>exposed to a bit of vibration so I have some concerns about securing the cpu.
>
>I know the easiest thing is simply to solder the pic direct to the board
>but I need
>the option of easy access/removal until everything is stabilized. It's
>close to that
>point where I am comfortable about the code but for a few that I want to
>let out
>now with a socket I am wondering if there is a way to nail the pic in place.

By far the most reliable method is to solder the PIC right into the
socket.  Use a machined pin socket that has nice, easy access to the pins
even after the PIC is installed.  When you are convinced that you don't
need any more changes, just solder the pins right where they enter the
socket.  Done!

dwayne

--
Dwayne Reid   <dwaynerspamKILLspamplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

Celebrating 20 years of Engineering Innovation (1984 - 2004)
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____________________________________________

2004\10\21@210918 by Bill & Pookie

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If you can put a large enuff hole on each side of the IC, you could tie  it
down with the waxed nylon cord that is used for tying wiring harnesses.  The
cord is a little wider than the width of a IC pin.  Lacing cord?

Bill

{Original Message removed}

2004\10\21@221625 by Russell McMahon

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> How about a blob of hot glue?

Hot glue loses its stickability - typically in about a year. Anything
relying on it for mechnical retention is a slow delay bomb.

> Maybe not a few strips of duct tape...

Not enough "command authority'

RTV is frowned on by certain specs (I think PP gave details on this at one
stage) but I have had it work reliably over many years in a VERY high shock
application. Some of my communicators get thrown around very
enthusiastically by children with intellectual problems. If sockets are used
unretained ICs creep out of sockets. RTV stops that. As someone else said -
a small dob at the ends is enough. Keep off pins. USE NEUTRAL CURE RTV - NOT
acetic acid cure.



       RM


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2004\10\22@024120 by David W.S. King

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Hi Josh

> Haven't seen you post in awhile. How's that ZIF socket I
> sent you working out?

It was a life saver right up till the programmer it was on died on me.
Had to grab a programmer and didn;t even think about cheaping out and
not getting another zif with it this time ;-]

{Quote hidden}

It sounds like a blob of rtv is going to be the way to go. I don't
think I can use a nylon strap or a solder cross strap so I'm "stuck"
with glue...

Dave

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2004\10\22@033659 by hael Rigby-Jones

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{Quote hidden}

I used to work for a company that made railway signaling equipment.
Vibration was a significant problem, both of train and track/trackside
mounted equipment.  IIRC any IC's that had to be removable (most always
EPROMS, and always DIP) were first soldered into a turned pin header which
fitted nicely into the turned pin socket on the PCB.  A small cable tie or
two would be threaded around the whole assembly.  Some kind of RTV style
compound was tried and worked ok, but left the sockets in a mess after a few
EPROM changes, and it was considered that there was too high a risk of
contaminating the the pins and sockets.

Mike

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2004\10\22@040317 by Wouter van Ooijen

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> Solder strap or wire across the pic?

two holes in the board and a plastic strap?

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


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2004\10\22@042539 by Alan B. Pearce

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>What else is there to try?  It needs to be able to
>allow some limited rework. ie pop the pic out and
>reprogram and reinsert so a thick conformal coating
>would be more trouble than its worth as an example.

The way we do this with space electronics is to have a gob of epoxy at each
end of an EPROM. Some gentle warming with a heat gun softens the epoxy
enough to allow it to be cut through with a scalpel to get the part out, but
it holds everything sufficiently to get it through the vibration tests and
launch.

____________________________________________

2004\10\22@224343 by Ken Pergola

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Alan B. Pearce wrote:

> The way we do this with space electronics is to have a gob of
> epoxy at each
> end of an EPROM. Some gentle warming with a heat gun softens the epoxy
> enough to allow it to be cut through with a scalpel to get the
> part out, but
> it holds everything sufficiently to get it through the vibration tests and
> launch.

Hi Alan,

Exactly. It's funny you mentioned this Alan. We used 3M/Scotch DP190 epoxy
in the past to do this before Flash PICs were the mainstream -- a little
blob at each end did the trick. The technicians would heat it up just as you
said, and "scalpel it" -- removal was pretty painless.

Best regards,

Ken Pergola


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2004\10\24@001457 by Ed Browne

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Dow makes a number of electronics grade non-corrosive silicone products that
have been used for years in high temperature down-hole drilling
applications.  Few electronics live in a higher vibration environment.  I
think 3145 is the preferred choice.

www.dowcorning.com/content/etronics/etronicsseal/etronics_aas_1ptov.a
sp


{Original Message removed}

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