De Solder SM electrolytic caps

Snap it in half and remove each end with micro soldering iron?

Two small soldering irons. The poor man's SM tweezers.

Jeff

Or an SMT tweezer iron tip. Just a couple bucks from digikey

Sometimes the glue securing the pads to the PCB is strong enough to allow a solder blob on each lead huge enough for the second to remain molten while the first is re-heated and the capacitor quickly, but gently, lifted off. If there's a hiss or a fishy smell, the leaked electrolyte definitely needs cleaning off with an ionic solvent and any nearby tracks inspecting.

I've done that but first used a Dremel to saw the cap in half then remove. Then an 80 watt tweezers tip iron and a jeweler's screwdriver. I used to work on hand held transceivers that were nothing but SMD and got some good practice.

You would think that it would be ok to sub a regular electrolytic for a s.m. one, but in my experience, it seldom seems to work, and I've never really figured out why, except that the ESR of s.m. caps seems to usually be considerably higher than that of the same value cap in a conventional wire ended package. Maybe the designers have to take this into account ? A classic example is the three little 47uF s.m. electros that you find on the servo board under some Sony CD mechs. These caps have a habit of leaking, and causing poor 'playability', but if you try replacing them with conventional electros, the servos barely work, if at all. Replace them with original surface mount types, and the performance is returned to 'ex-factory'.

As for getting the little muthas off the board, I tend to flood the pads with new solder first (always nice low melting point leaded, even if the board is constructed in lead-free), and then heat one side and lift gently with a scalpel tip, and then repeat for the other end. In stubborn cases, like others have suggested, I use two irons, with their temperatures cranked well up ...

Arfa

Jeffrey D Angus wrote in news: snipped-for-privacy@news5.newsguy.com:

solderwick is noted for removing SMD pads; you have to apply too much heat to get the wick hot enough to wick up solder.

get a soldering iron that will accept a 6/32 screw where the tip belongs,then cut and form some thickwall copper tubing into an L shape,with a notch on one side that fits the SMD you're trying to unsolder. then drill a hole for the 6/32 screw on the other side of the L. you've just made a custom SMD desoldering tip for caps or resistors. you'll need several different sizes.

I routinely re-cap Tektronix acquisition boards from TDS series scopes. I've found the best way is to cut them close to the board - right where the can dimples in a bit. Then I just flick the remaining part of the can and plastic off with an x-acto knife, and remove each leg with a soldering iron. There's about 70 in each scope, and I've probably done 50 scopes in all. Never damaged a single pad.

Well,

Here is an odd possibility. One brand of stereo I service has a mod that require removing 16 SM caps from a PC board. (That's the entire mod). In speaking with a friend who also services these, he suggested grabbing the cap with a pair of needle nose pliers and rotating the cap until the leads snap. This usually requires about 90 degrees of rotation. Then it's easy to clean up the pads. The caps are 10uf/16V and have a black plastic base.

I'D SUGGEST TRYING THIS NO A SCRAP BOARD FIRST, as some boards may not have the foil attached as well as these.

Regards, Tim Schwartz Bristol Electronics

Tim Schwartz wrote in news: snipped-for-privacy@bristolnj.com:

SM caps don't have "leads". SM = surface mount. Just get or make the right tool for the job.