Surface mount capacitors

[chris ma]

I have tried surface mount polar caps and my experience with them was not very good. The flimsy little flaps are too fragile and broke off very easily. And they are really too small for hand soldering.

Please tell us what you experience with them. What is the best way to solder them?

Chris

[azira]

Are you talking like chip capacitors/resistors? Tin the pads first then place the cap/resistor/chip on the pad. Apply heat to the pad/device and when the solder heats up, the device will "sink" into the pad.
Same trick works for SMD ICs too.
--
Danny

[jackinnj]

i do the toaster oven method -- now probably on my 20th project -- I use a ultrafine tweezer to apply the solder paste -- I have a loupe which, when reversed, magnifies beautifully -- then carefully place the resistors, caps and IC's onto the pads -- of course it helps if you don't drink a lot of coffee.

they take about 2 1/2 to 3 minutes in my special purpose toaster oven - the board will start to fry if you go any longer. obviously, since there are lead fumes involved you don't want to use the toaster oven for any purpose dealing with food.

quite frankly, smt's make it a lot easier to work and the precision of the parts is excellent -- typical matching of resistors on the same reel is usually around 0.1% to 0.5% for resistors -- as if you are making your own filters or differential amplifiers -- are a boon. further, smt opamps, voltage regulators, gate-drivers even the high quality items, seem to be much less expensive and more plentiful on EBay.

[chris ma]

One advantage with the surface mount caps is that no holes are needed to be drilled on the pcb.

[Stocker]

what sort of temperature do you use in the oven? I guess it would depend on the solder.

[jackinnj]

Originally posted by Stocker
what sort of temperature do you use in the oven? I guess it would depend on the solder.

425 F -- or so the setting says on the dial

i've only turned one board to "goo"

[ingvar ahlberg]

The "toaster oven" method is´nt really right for smd soldering, for reflow soldering You need an extremely tight control of heat curve: preheating to activate flux in paste- reflow- rapid cooling.
Precision in chipresistors is good but it is still lousy resistors, You can find metalfilm resistors in melfpackages but nothing close to the quality of even the most comon through hole metal film resitors. SMD/SMT is all about producing high volume cheaply.
SMD semiconductors are as good as throug hole types, but filmcapacitors, for instance, are rotten and seldom survive soldering. Drill holes, if You´re not into making cellular phones

[contaxchen]

hello,

I want to know how to tell the anode from the cathode for a surface mount eleclytic cap....
I just recieves a bunch of surface mount sanyo os con. I don't understand the marking on them. It's my first time to use them.
If i use my DMM to test its voltage for both ends, I probably can see which one is the cathode. In case that the caps are too old, this method could be indeterministic. Just give me a hint!
CC

[chris ma]

Originally posted by contaxchen
hello,

I want to know how to tell the anode from the cathode for a surface mount eleclytic cap....
I just recieves a bunch of surface mount sanyo os con. I don't understand the marking on them. It's my first time to use them.
If i use my DMM to test its voltage for both ends, I probably can see which one is the cathode. In case that the caps are too old, this method could be indeterministic. Just give me a hint!
CC

There should be a marking of a darkened BAR on the top of the cap to indicate the negative side of the leg at the bottom.

Hope this help.
Chris

[contaxchen]

HELLO,
Darkened bar? There is a darked side on the top of the caps.... But it gives postive voltage...
What should I do?
I think the SMD caps follow the same tradition as conventional ones, but... most of my caps' darked side shows they are anode...
I will just follow what you said.
Thanks
lhchen