Is the resistor exterior coating of the appropriate thickness and
material, dielectric? Does solder thickness/uniform meet spec?
Victor,
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Nutting
Sent: Monday, August 20, 2007 7:43 AM
To: [log in to unmask]
Subject: Re: [TN] Solder mask as an insulator - illustration posted
These are all very good suggestions. Many of them have been tossed
around as solutions and each had attributes that put them on the not
preferred list. My concern is not adding extra assembly steps or labor
to the existing design. Ease of manufacture is the direction I'm
supposed to point our designs. The real secret will be to find a way to
fix the problem without adding any impact to assembly. Redesigning the
bare circuit board my be the best alternative to not incur extra
assembly steps or cost. And making this a check point in design reviews
in the future to eliminate it before we see a failure in the field.
Phil
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Whittaker, Dewey
(EHCOE)
Sent: Friday, August 17, 2007 3:44 PM
To: [log in to unmask]
Subject: Re: [TN] Solder mask as an insulator - illustration posted
Phil,
I guess the few simplest ideas left that I have are as follows:
* Prep the axial leads with a frog leg bend so the part will be
above the surface after installation prior to soldering
* Prep the part with one frog leg bend and mount the part with
the u-bend if you have height clearance
* Sleeve the body with heat-shrink sleeving prior to
installation
* Dip the body of the part in Type UR Conformal Coat per
IPC-CC-830
There are others, but you seem to have reluctance at doing anything to
the bare printed board.
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Craig Cullum
Sent: Friday, August 17, 2007 7:21 AM
To: [log in to unmask]
Subject: Re: [TN] Solder mask as an insulator - illustration posted
Aaaaah. I've experienced something similar in the distant past when
hand-assembling prototypes and such.
The cover (epoxy?) of metal-film through-hole resistors is not as
structurally sound as one would presume.
Craig Cullum, Engineering Technologist, AMTELCO
e: [log in to unmask]
[log in to unmask]
f: 608 838 8367
v: 608 838 4194, or 4197, x128
Please visit us at www.amtelco.com
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Nutting
> Sent: Friday, August 17, 2007 7:15 AM
> To: [log in to unmask]
> Subject: Re: [TN] Solder mask as an insulator - illustration posted
>
> Good Morning folks,
>
> I created a graphic to illustrate our "punch through" problem
> as I don't have any photographs of the failed board/part.
>
> Steve Gregory has posted the illustration at
> http://stevezeva.homestead.com/files/LPI_punch_thru.jpg.
> Thanks Steve.
>
> Phil
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