Problem with SM caps

[Charlie E.]

Hi All,
Ok, after never before having an opportunity, I designed my new boards
with SM caps. Didn't think there would be any problems soldering
them, but have run into a real problem.

Every single dang one of them shorts out when I solder them down. They
are Murata 0805 caps, and the only thing I can think of, is that there
is this little metal 'clip' on each side that must be shorting the
pads together. if if remove one of the caps, it is definitely not
shorting internally.

I just used the standard 0805 footprints in the Orcad Layout library,
and haven't had any problems with the resistors, just these darned
caps! Has anyone else seen problems like this? Or am I just making
some simple newby mistake?

Thanks,
Charlie

 

[nospam]

are Murata 0805 caps, and the only thing I can think of, is that there
is this little metal 'clip' on each side

Errm, I think the little metal 'clip' is supposed to be on each end.
--

 

[[email protected]]

Hi All,
Ok, after never before having an opportunity, I designed my new boards
with SM caps. Didn't think there would be any problems soldering
them, but have run into a real problem.

Every single dang one of them shorts out when I solder them down. They
are Murata 0805 caps, and the only thing I can think of, is that there
is this little metal 'clip' on each side that must be shorting the
pads together. if if remove one of the caps, it is definitely not
shorting internally.

I just used the standard 0805 footprints in the Orcad Layout library,
and haven't had any problems with the resistors, just these darned
caps! Has anyone else seen problems like this? Or am I just making
some simple newby mistake?

Thanks,
Charlie

Which part number?
Are the boards clean?
How are the parts being placed? By machine? Pick and place?
How are they soldered? By hand? Reflow?
Are you using lead-free solder?
What kind of solder paste? How big are the mask openings?
Are you using a different footprint for the caps? Maybe there's a
problem with that symbol?

 

[Charlie E.]

Which part number?
Are the boards clean?
How are the parts being placed? By machine? Pick and place?
How are they soldered? By hand? Reflow?
Are you using lead-free solder?
What kind of solder paste? How big are the mask openings?
Are you using a different footprint for the caps? Maybe there's a
problem with that symbol?

Ok, they are new boards being hand soldered by yours truly. They are
clean, and I am using standard thin (.032) solder from Radio Shack.

Bad new is, I just looked at one that I pulled off the board, and it
IS shorted internally. great, they must be sensitive to solder
temperatures...

BTW, the clip is the end clips, they just have these little bits of
metal holding the sides in.
Charlie

 

[Charlie E.]

Ok, they are new boards being hand soldered by yours truly. They are
clean, and I am using standard thin (.032) solder from Radio Shack.

Bad new is, I just looked at one that I pulled off the board, and it
IS shorted internally. great, they must be sensitive to solder
temperatures...

BTW, the clip is the end clips, they just have these little bits of
metal holding the sides in.
Charlie

the clips are NOT the end clips...

 

[linnix]

Ok, they are new boards being hand soldered by yours truly. They are
clean, and I am using standard thin (.032) solder from Radio Shack.

Bad new is, I just looked at one that I pulled off the board, and it
IS shorted internally. great, they must be sensitive to solder
temperatures...

Yes, it does happen, but usually just a small percentage. We are
using 0604 104 (0.1uF) and 105 (1uF) caps without much problems. You
might just have a bad batch of chips. What capacity are they?

 

[Charlie E.]

Yes, it does happen, but usually just a small percentage. We are
using 0604 104 (0.1uF) and 105 (1uF) caps without much problems. You
might just have a bad batch of chips. What capacity are they?

several different valued, from .22p to 1u, even one tant that may have
been ok, but when I removed it, it went 'ping!'

Charlie

 

[linnix]

several different valued, from .22p to 1u, even one tant that may have
been ok, but when I removed it, it went 'ping!'

Charlie

What iron are you using? Try with 20W or less.

 

[Charlie E.]

What iron are you using? Try with 20W or less.

I am using a Hakko 936 solder station, set at about 660...

 

[Rich Grise]

Ok, after never before having an opportunity, I designed my new boards
with SM caps. Didn't think there would be any problems soldering
them, but have run into a real problem.

Every single dang one of them shorts out when I solder them down. They
are Murata 0805 caps, and the only thing I can think of, is that there
is this little metal 'clip' on each side that must be shorting the
pads together. if if remove one of the caps, it is definitely not
shorting internally.

I just used the standard 0805 footprints in the Orcad Layout library,
and haven't had any problems with the resistors, just these darned
caps! Has anyone else seen problems like this? Or am I just making
some simple newby mistake?

Maybe a dumb question, but are you installing them backwards?

Good Luck!
Rich

 

[Charlie E.]

These parts usually have two plated "end caps" that wrap all the way
around, with a nice middle band of ceramic.

We hand-solder parts like this all the time and essentially never have
shorts. Could your iron be way too hot?

A good temperature-controlled iron, preferably a Metcal, is worth it.

John

Hmmm... I have my Hakko set to approx. 650F. Anywhere you know of
what the standards should be?

Charlie

 

[Charlie E.]

Maybe a dumb question, but are you installing them backwards?

Good Luck!
Rich

All but one are standard ceramics, so no, shouldn't be. My first
thought was teh tantalum, which went byebye when I tried to test it...

Charlie

 

[Charlie E.]

The recommended setting for the Hakko 900 series tips varies. As I recall,
the smallest tips should be set to 400C. So, your 650F should be okay for
the tip.

Soldering smt ceramic caps with soldering irons (and wave flow) is rough on
them because of the high dT/dt. If I have to use a soldering iron, I only
apply the soldering iron tip to the pad and allow the solder to flow to the
cap's termination. I'm sure how much this really helps reduce the thermal
shock.

When 1uF first came out in a (then relatively) small 1812 package, I had a
lot of problems with them becoming leaky after IR reflow. The only solution,
according to Novacap, was to reduce the dT/dt rate in the reflow process. We
required that the CM to incorporate this change and it seemed to have solved
the problem.

The best thing to do is to use a hot air tool on these sensitive parts.

Bob

Ok, these things are driving me crazy.

Took a new cap out, soldered one end with iron set at 500F. Shorted!

Took another new cap out (1uF both) and tested it. SHORTED! Using my
analog VOM, with two AA batteries, so it can't be overvoltage (10V
parts...) so, did I just get a bad batch from Digikey!!!!!!??????

In three different ratings??????

Charlie

 

[Eeyore]

Which part number?
Are the boards clean?
How are the parts being placed? By machine? Pick and place?
How are they soldered? By hand? Reflow?
Are you using lead-free solder?
What kind of solder paste? How big are the mask openings?
Are you using a different footprint for the caps? Maybe there's a
problem with that symbol?

Are you using a glue before soldering ?

I've had no trouble (except with my eyes) soldering 0805s by hand. Takes a
while to recover normal vision.

And the buggers tend to stick to the tip of the iron, so held 'em down at
one end (say with a toothpick) while soldering the other. Then do the other
end.

Sneezing is also a bad idea.

Graham

 

[Eeyore]

BTW, the clip is the end clips, they just have these little bits of
metal holding the sides in.

Uh ? <perplexed>

Graham

 

[Eeyore]

I am using a Hakko 936 solder station, set at about 660...

Fahrenheit one assumes ?

Sounds WAY too low for me. I like to solder FAST and get out of there fast. Causes
less potential damage IMHO and IME. 800F for me.

Graham

 

[Eeyore]

The best thing to do is to use a hot air tool on these sensitive parts.

And blow them away ! ;~)


Graham

 

[James Arthur]

Hmmm... I have my Hakko set to approx. 650F. Anywhere you know of
what the standards should be?

Charlie

650F should be fine.

I've soldered countless SMD caps, no failures. I've even desoldered
and resoldered a few times tweaking protos. The terminations
eventually peel off, but I've never had one short. Never.

Something else is wrong.

Maybe:
test cap first,
then apply iron--to one end only--of bare cap,
then a dab of solder to each end,...

Test for 'short' each time...

Another idea: use an ohmmeter to try to find the short's
location. Inside the cap, or on the surface?

Could be it's a bridge from soldering, on the outside.

HTH,
James Arthur

 

[James Arthur]

Uh ? <perplexed>

Graham

Also perplexed. SMD caps don't have "bits of metal" holding their
sides in, just the metallized contacts at the ends.

ceramic
/
..--.-------.--.
| | | |
| | 0805 | |
| | | |
'--'-------'--'

\ /
\ /
\ /
metal
contacts

Cheers,
James Arthur

 

[James Arthur]

Fahrenheit one assumes ?

Sounds WAY too low for me. I like to solder FAST and get out of there fast. Causes
less potential damage IMHO and IME. 800F for me.

Graham

650 might be a little cool. I prefer 675-ish F, sometimes go 700 F
with 63/37. But 650 F will work.

Lead-free solder takes higher temps, of course.

James Arthur