Problem with SM caps

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

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

the clips are NOT the end clips...

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

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

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

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

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

Good Luck! Rich

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

Charlie

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

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

Charlie,

Get some solder paste, a hot air tool, and you'll be joyful.

Bob

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

Your iron is way too cold. 750F/400C is the ticket. Using too cold an iron makes the part stay very hot for far too long.

Cheers,

Phil Hobbs

Your iron is way too cold. 750F/400C is the ticket. Using too cold an iron makes the part stay very hot for far too long.

Cheers,

Phil Hobbs

I've had parts leap onto the iron--dancing and swimming in molten solder while I tried to wipe 'em off--without damage. I don't know why Charlie's would fail so easily. Something's wrong.

And you'd expect thermal shock cracks from soldering would create opens, not shorts.

On low mass jobs I keep the iron on the cool side, but hot enough to work quickly. A well-tinned iron helps.

I'm still puzzled by the "bits of metal holding the sides in" Charlie wrote of earlier.

Cheers, James Arthur