Nagging Noob Questions

[Mr Phil]

Relative Noob here. I've completed a few projects with success and trying to improve as I go. Below are few nagging questions that I can't seem to get a clear answers from searching this forum or general web search. Feel free to link to another thread, maybe I'm using the wrong keywords. Thanks in advance.

Why is it necessary to clean all solder flux from PCB's? Here is what I've gathered so far:

• Looks better. I agree with this, but for most projects I don't care.
• Helps check for solder bridges. I agree with this, but I'm confident I can check for bridges with limited cleaning, magnification, and a bright light.
• Long term corrosion. I've been using SRA Rosin Paste Flux #135. This product claims it does not need to be cleaned and "the rosin also leaves a protective coating over the soldered area that can prevent corrosion." This stuff is likely more messy than a flux pen, but I've had good results so far.

Why use Tantalum capacitors? I've never used them, but I see they are quite common on various build reports. I've generally used ceramics for pF, film for nF, and electrolytic for uF and have a decent stockpile of each.

• Why are tantalum caps better? How much difference do they really make?
• Seems like the general recommendation is to use them in the signal chain. Are there any advantages to use them in other locations?

 

[chongmagic]

I am not going to lie, I read this title as Sagging Boob questions.

I always clean my PCBs just to see if there are any signs of a possible cold solder joint, and some flux residue does cause damage over time. I use no clean solder but I still clean my with IPA.

People use tantalum caps in place of electrolytic caps because electrolytic caps are prone to leakage.

 

[Vildhjuggah]

You sound like someone who needs to be told to clean their room. (sorry if thats too rude but your making excuses to clean up so you do)
Another good reason is so random little bits of metal (ie clipped leads or metal shavings from the drilled box) don't stick to the flux and short something out.
and if flux is so good for boards why don't they tell us to just wipe it on everything to protect everything from corrosion?

Googled tantalum vs electrolytic and this is the first thing i found.
"However, tantalum oxide capacitors have a much higher capacitance value for their size. They are more expensive than aluminum oxide, but they are more reliable, more stable and they operate better at certain frequencies "

If you google tantalum vs ceramic you will find good info as well.
Articles related to this mention some good uses in power circuits (mostly high voltage) and that depending on the use, modern mlccs may or may not be just as good.
But also ceramic caps are microphonic/piezeoelectric.

 

[zgrav]

clean boards are more reliable, limit problems you would otherwise encounter.
tantalum caps are much smaller, and provide better builder choices in tight builds.

 

[Barry]

I am not going to lie, I read this title as Sagging Boob questions.

I always clean my PCBs just to see if there are any signs of a possible cold solder joint, and some flux residue does cause damage over time. I use no clean solder but I still clean my with IPA.

People use tantalum caps in place of electrolytic caps because electrolytic caps are prone to leakage.

You've been in quarantine too long!

 

[Gordo]

I'm in the "need to be told to clean their room" camp. I most certainly need to clean my workbench

I'm guilty of not cleaning my boards nearly enough but have had very few problems with it. I assumed "no clean" was a direct order. That said, I have to admit that for troubleshooting it's invaluable and it certainly looks nicer, especially if you top solder.

The biggest difference with Tantalums is how they fail. It's really not critical with the voltages we're dealing with but tants will fail in a shorted state. Electros usually fail in an open state. I'd heard for years that tants were bad in the audio path but that's pretty much chalked up to cork sniffery.

 

[mywmyw]

Careful soldering should theoretically be enough to avoid problems - perhaps you don't *need* to clean your boards. But why skip this step? Takes about a minute. Think of it like brushing your teeth. Saving a few minutes but ruining your mouth is silly.

 

[Chuck D. Bones]

Tantalum caps are more transparent at audio frequencies. If you want the sound of electrolytics, or need them cover up deficiencies in other parts of the circuit, then they might sound better than tantalum. Cork sniffing, or maybe glue sniffing.

 

[Gordo]

Haha!!!

 

[twebb6778]

The mining of tantalum, mostly in the Democratic Republic of Congo, is questionable from an ethical perspective. The people who work in these mines are often doing so under military duress and in incredibly poor conditions. If you're going to use tantalum, do some research to find out how it's sourced.

 

[Chuck D. Bones]

AFAIK, all of my tantalum capacitor bought in the last several years are AVX.

https://www.businesswire.com/news/h...s-Guarantee-Conflict-Free-Tantalum-Capacitors

 

[Gordo]

I did not know this was a thing. Thanks for bringing this to our attention!

 

[Barry]

I did not know this was a thing. Thanks for bringing this to our attention!

Ditto, will be buying AVX going forward!