Richard,
With what you said, you will never and I say NEVER have a problem as we are a manufacturer that now only
uses exactly what you described. I sent an e-mail to let the originator of this thread know that it is
either heat related or he is manually inserting the LED's with a standoff of less than 0.075". We ran into
a problem exactly like this years ago and found that when you manually swage the leads via a person with
an air operated swager, they will press down on the top of the part, and tighten the lead 90 degrees to the
board. This stresses the die internally and heating it during soldering doesn't help. We had parts fail
at the pot and soon after. If these two things can be avoided, the problem goes away, but then again
you're all set.
P.S. just put in a Rain Bird Sprinkler system this year and LOVE it. Pass it on as my brother works for a
competitor and I wouldn't touch him with a 10 foot Toro pole...ooops gave that one away <G> ;-)
Mark Ross
Sr. Design Engineer
Whistler Auto-Mation Products Inc.
Hamilton, Richard -4454 wrote:
> Hey Gang,
>
> Well, as one of the working few (I love my boss; I love my boss; I
> lo.......), I too have a couple of products that make extensive use of PTH
> LED's, and unlike Evan, we have never had to elevate them from the surface
> of the PWB.
>
> We have not seen any problems with the LED's either at In-Circuit or
> Functional testing, nor are we hearing about any field problems with them.
>
> Our process consists of automatic insertion via a radial machine, conveyor
> to work stations and into the wave solder machine. The radial machine has
> verification and lead cut-n-clinch on it.
>
> I just thought of one other factor that *may* have an effect here, we make
> our holes .014" over lead size and off the top of my head I am not sure how
> we handle the square lead issue on the LED's, but if you think it may be
> significant, I will dig into this.
>
> Anyway, good luck.
>
> Richard Hamilton
> Clemar Mfg. / Rain Bird
> [log in to unmask]
>
> > -----Original Message-----
> > From: Evan D Jones [SMTP:[log in to unmask]]
> > Sent: Tuesday, December 29, 1998 3:22 PM
> > To: [log in to unmask]
> > Subject: Re: [TN] Assy: LED Failures...
> >
> > Steve,
> > I recall having a LED failure problem on a product once. We found
> > that
> > the particular type of PTH LED (can't remember the brand) would have a
> > higher rate of failure when wave soldered with the led mounted flush to
> > the
> > card. By standing the LED off the card the problem went away. We never had
> > time to get to the bottom of the problem, ie was it flux getting into the
> > part, or due to overheating. But by standing the part off the card the
> > problem went away.
> >
> > Regards Evan
> >
> > Evan Jones
> > Manufacturing/Test Engineer
> > Bluegum Technology Pty Ltd
> > PO Box 609, Wangaratta, Australia, 3676
> > Ph: 61 3 5720 2539 Fax: 61 3 5720 2412
> > Internet: [log in to unmask]
> >
> >
> >
> >
> > Tom Braswell <[log in to unmask]> on 30/12/98 07:28:09
> >
> > Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please
> > respond
> > to Tom Braswell <[log in to unmask]>
> >
> > To: [log in to unmask]
> > cc: (bcc: Evan Jones/BGT)
> > Subject: Re: [TN] Assy: LED Failures...
> >
> >
> >
> >
> > Steve,
> >
> > We use alot of PTH LEDs, as far as I know , I dont believe we have seen
> > this
> > problem with PTH, we have with SMT LEDs, diffuser breaking off due to
> > incorrect heat and handling problems.
> >
> > This might seem like a dumb question but are the replaced LEDs passing
> > test
> > or failing after extended power on times?
> >
> > How do the failed LEDs test with DMM out of Circuit?
> >
> > Can you perform a functional test on removed LED with 1K resistor and 5vdc
> > source, this will put 5ma of current, (should not damage
> > LEDs, its less than 25ma) to see if they emit light?
> >
> > I'm wondering if it is EOS (electrical over-stress) too much current,
> > design
> > flaw or wrong component may be damaging them?
> >
> > If not "test kills" then forgrt my ramblings!
> >
> >
> > Tom Braswell
> >
> > -----Original Message-----
> > From: Stephen R. Gregory <[log in to unmask]>
> > To: [log in to unmask] <[log in to unmask]>
> > Date: Tuesday, December 29, 1998 3:06 PM
> > Subject: Re: [TN] Assy: LED Failures...
> >
> >
> > >In a message dated 12/29/98 11:29:21 AM Pacific Standard Time,
> > [log in to unmask]
> > >writes:
> > >
> > ><< Are your LED's surface mount or through hole?
> > > >>
> > >
> > >Hi Mark!
> > >
> > > Yeah, 'bout your plant shutting down over the holidays, same here
> > too.
> > We
> > >were SUPPOSED to be shut down too, but a customer brought this kit of
> > >transceivers over along with another job that they just HAD TO HAVE back
> > >before the first of the year... you know how that goes. I guess there's
> > one
> > >thing good about working now, don't have to deal with the gridlock we
> > have
> > >here in "Silicon Valley" going to and from work 'cause everybody else is
> > >off...just gotta' be able to see through the fog (it's literally been as
> > thick
> > >as pea soup out here the last few days)
> > >
> > > Where were we? Oh LED's...the ones I'm dealing with are PTH, little
> > radial
> > >square buggers, about .250" square. They go on a .040" stand-off too. I'm
> > >using the same kind of parameters that I wave most of my boards with, you
> > >know, nothing unusual. This board does have surface mount on the bottom
> > so
> > I'm
> > >using a chip-wave too. I've waved other boards with PTH LED's before and
> > not
> > >had as many dead ones as I'm getting now...
> > >
> > >-Steve Gregory-
> > >
> > >################################################################
> > >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
> > ################################################################
> >
> > ################################################################
> > 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
> ################################################################
################################################################
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
################################################################
|
