Problem with SM caps

I desolder parts by laying a big iron tip across both ends, melting everything in sight, and knocking the parts aside. Doesn't seem to bother them.

About the only damage I see from soldering abuse is ripped-off end caps, and that seldom on PC boards.

John

You do everything on how it seems to you, John. That is a problem, but I am sure you have also 'knocked that part aside' as well.

Except that you obviousl;y have no clue what soldering abuse is. The two irons violates several rules regarding PCB assemblies.

Ceramic Multi-layers Chip Capacitors DO get damaged, particularly by high solder and reflow temps. They are meant for ONE solder operation.

If you are repairing a circuit, you should replace any removed chip caps.

Despite them possibly appearing intact, they detach from their termination end caps internally, ESPECIALLY when some know nothing dope uses TWO irons at high temp to remove one.

The best way to perform a removal and still keep the part and its operational parameters intact, is to use solder braid ON the solder joint at each pad, ONE at a time. Quickly removing the main bulk of the solder fixturing it in place. Then, the part can generally be removed clean and relatively cool. I would still replace any chip cap, however, as I have seen them get damaged from heat, and the problem become severely apparent when working with HV chip caps.

Two irons for placement or removal of an SMD part is the stupidest thing any assembler (that's barely what you rate) could ever do.

Despite any circuit level engineering you may posses, you certainly lack a lot of knowledge in physics. The vapor phase, and now this certainly proves that.

Yeah, but this one was DOOB (or out of tape!) I have tested this in both the 1uF and 22pF caps. very, very weird!

Charlie

Well, they are in the packaging that digikey sent them in, in a sealed tape. But then, maybe DK did something wrong. the parts have no markings on them. The resistors do have values on them.

Charlie

Yes indeed, the two end terminals, marked 1 and 3 in the page below, are electrically connected, and the capacitance is between either of those and terminal 2, the 'center clip' area, or as called in an earlier post, "the metal holding the sides in" (the above page points to this datasheet):

No wonder the two endcaps are shorted together, it's designed that way.

That looks like an "SMD feedthrough (pat. pend.)"

It is an EMI filter. Jeez! Learn how to read a datasheet.

Chip EMI Filters Capacitor Type.

"NFM21PC Series: NFM21P is a 3-terminal structure component. This product can be applied to large current DC power lines. NFM21P is suitable for noise suppression of DC power lines where relatively large current operates."

Your problems aren't my problems.

What two irons?

How am I supposed to remove a part from a board without a second soldering operation?

Of course. But there's nothing keeping me from measuring a part I just pulled. I often do, just to make sure it wasn't the wrong value... especially with so many resistors now having goofy or even no top marks, and caps having none at all.

What two irons?

I'd rather trash the part than the board, so I want zero removal force on the pads. So I prefer both pads to be molten when I lift the part.

On parts with a lot of pins, I can sometimes cut the pins off the part, and then desolder them one at a time. Or just send it downstairs to the production people, who have every rework gadget imaginable.

What two irons? On my bench in my office. I only have room for one Metcal.

ftp://jjlarkin.lmi.net/DSC01371.JPG

Two semisters at Tulane, both A's. How about you?

John

Two questions, zero answers. On that basis, I can't help much.

John

Hi Everyone, Ok, mystery solved. These things aren't caps, they are little EMI filters! They popped up when I did my search of the Digikey database when I was ordering, and in my error, I saw "filter, cap" and thought that meant a filter cap, not a filter that contains a cap. Of course DK is doing the right thing, and refunding my purchase and shipping my replacements free, but they are also going into the web guys, and making sure that a search for capacitors doesn't bring up filters!

Sorry to drive ya'll as crazy as I have been... 8-)

Charlie

Hi John, Thanks for your help. Yep, they are not caps, but 'filters' that came up when I searched for caps. Mea culpa! I 'assumed' that if you searched for caps, you got caps, and didn't get and examine the data sheets for every part. I just needed a few bypass caps... :-(

Charlie

That would do it.

RL

This explains the metal 'clip' on the sides.

RL

I was about to ask: Are you sure they are not ferrites?!

ROFL

We have a soldering iron that looks like a pair of tweezers. Both ends get hot and one just plucks the parts off. I don't like using it to solder parts back on because its tips are crap.

I just lost some pads because I had to solder a resistor to the board as a probe point. The scope probe got bumped and the whole mess came off. I spent an hour soldering wires and gluing down PTH resistors to get the board working again. :-(

Caps may "measure" at one value, but perform at an entirely different way. HV caps cannot be "measured" to determine viability. They actually have to be energized at HV voltages to detect a failure mode. Some are detectable as they became wholly shorted.

Replace and be sure. Put that part back down that you removed in such a lame way, or even 'the right way' makes it a used part, and your product is no longer "new", nor does it carry the specified MTBF declared for it.

I have you on this one, Johnny. You know NOTHING about chip caps and heat or degreasers, after what you wrote.

That depends on the form factor, and what brand they are. There are plenty of chip caps that have markings. Just not any that would be visible to such a technically casual dipshit as yourself. It would require that you actually pay attention to the details, instead of the typical male 'Ram it, Cram it, Jam it, damn it' mentality. Added together with that 'knows all' attitude, and you are seen as the half assed prick that you are.

That is the ONLY correct way to remove the part, if the part is not to be reclaimed. So, you got one right. Someone in your employ must have actually known what he was doing at one time, and instructed you.

If they would remove the part in any way other than that you described, they would be doing it incorrectly. The ONLY time heat should be applied to the assembly is for BGA where the connections must all be reflowed at once, or other such parts that need full reflow for removal. If the pins are exposed, a proper rework tech will NOT apply heat to remove a part which will not be salvaged.