I have not substitute TH caps for SM Caps in high
volume production; however, to solve the crack cap
problem we had due to stress or board flexing, we
relayouted the board and substituted two smaller caps
for the larger value parts. It was not a vendor
problem because we have mulitiple vendors on the AVL
Ted
--- "Bissonnette, Jean-Francois"
<[log in to unmask]> wrote:
> I'll see what I can do for the pictures.
>
> The cracking are near the end terminasion. They are
> called "flex-cracks"
> apparently due
> to flex of the boards but the boards they're
> soldered on are rather thick
> we're not sure.
> And there is a variety of reasons why these
> appeared. What we're facing now
> is more
> can we do it another way so these cracks are not
> appearing? The TH part
> seems to be
> the most economical way, on short term that is. But
> I've seen more than
> enough situation
> where economical way turn out to be "pay now or pay
> (more) later".
>
> I want to know if anyone tried it the way I said
> before and what they came
> up with.
>
> Here is a link to a report on these cracks. It may
> interest some of the
> technetters.
>
> http://www.syfer.com/ta_02.htm
>
> -----Original Message-----
> From: James TerVeen [mailto:[log in to unmask]]
> Sent: Wednesday, February 12, 2003 10:48 AM
> To: TechNet E-Mail Forum.; Bissonnette,
> Jean-Francois
> Subject: Re: [TN] TH capacitor on SMT pads
>
>
>
> I guess coming from a Chip manufacturers side I need
> to ask Why you do not
> change suppliers. What kind of cracking are you
> talking about. I ask
> this because I just did a long process of tracking
> down a cracking problem
> with a customer and the final result was they had to
> much pressure in
> placing the component and were cracking it there.
> Very small cracks but
> they were there and when they fired up the board the
> cracks got much
> larger. Can you supply a picture of the cracks to
> Steve so we can take a
> look.
>
>
>
>
> "Bissonnette,
>
> Jean-Francois" To:
> [log in to unmask]
>
> <JBissonnette@WAB cc:
>
> TEC.COM>
> Subject: [TN] TH capacitor
> on SMT pads
> Sent by: TechNet
>
> <[log in to unmask]>
>
>
>
>
>
> 02/12/03 10:24 AM
>
> Please respond to
>
> "TechNet E-Mail
>
> Forum."; Please
>
> respond to
>
> "Bissonnette,
>
> Jean-Francois"
>
>
>
>
>
>
>
>
>
> Hi Technetters,
>
> We're having problem with some multilayer ceramic
> capacitors (SMT), they
> crack. We have a
> high level of rejects from the field and we're
> thinking of replacing them.
> However, the
> best that the design team came up with so far is to
> use regular ceramic
> capacitor (TH)
> (... please don't ask why they don't chance
> supplier... I already did and
> well, forget it!)
>
> I'm not too confortable with that, but on the other
> hand, a design change
> on
> the board
> would be very costly and we want to avoid that.
>
> Did anyone ever changed a SMT part for a TH part?
> What problems should we
> expect
> if we decide to go that way? Of course assuming
> that the leads would be
> bent properly, the
> cap would be bonded to the board, every applying
> rule for soldering would
> be
> respected and
> Murphy won't show its ugly face... then again we all
> know what appends when
> we assume...
>
> I'd prefer to go another way but my way will cost a
> lot of money and I'm
> told that we have to
> keep it to a minimum.
>
> Any thoughts?
>
> Jean-François Bissonnette
> Vérificateur, Contrôle de la Qualité
> Électronique
>
>
>
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