SMD soldering

[pickdropper]

Yeah, Surface mount isn't too bad until you have to do this:

[muddyfox]

I'm sorry folks, I need to keep this going... 

Two points I came across in my web preparation that I'm now unsure of.
- apparently it's recommended not to mix fluxes - would I have problems with using Kester 951 noclean pen and what little rosin (resin? never sure which) core there is in 1mm solder?
- noclean fluxes and potential for corrosion later on? Supposedly it's noclean but I'm sure it leaves something on the board and I can't really tell how conductive or corrosive it may be long(ish) term.

I'm sure these questions will seem quite silly a year down the road but right now they are a big deal. 

[stevie1556]

I'm using 0.3mm solder with flux in it (chinese seller on ebay), and a cone tip (I use the same tip for through hole stuff as well).

Sent from my thumbs using Tapatalk!

[Govmnt_Lacky]

Does anyone have input on the solder paste/heat gun idea? Would like to get some feedback on it as it seems like a clean, easy way to solder SMD 

[pickdropper]

I'm sorry folks, I need to keep this going... 

Two points I came across in my web preparation that I'm now unsure of.
- apparently it's recommended not to mix fluxes - would I have problems with using Kester 951 noclean pen and what little rosin (resin? never sure which) core there is in 1mm solder?
- noclean fluxes and potential for corrosion later on? Supposedly it's noclean but I'm sure it leaves something on the board and I can't really tell how conductive or corrosive it may be long(ish) term.

I'm sure these questions will seem quite silly a year down the road but right now they are a big deal. 

I can say that I absolutely detest the Kester 951 noclean flux, but that is just my opinion.  I FAR prefer the Kester 186 RMA flux.

[pickdropper]

Does anyone have input on the solder paste/heat gun idea? Would like to get some feedback on it as it seems like a clean, easy way to solder SMD 

I've only used solder paste prior to reflowing in an oven.  With passives, it's pretty easy, but with more complicated boards that have a lot of multipin packages, it's better do it with a stencil. 

I was surprised at the learning curve with applying paste through the stencil, actually.  It's easier than doing it by hand, but takes a bit of practice.

Oven/heat gun is definitely faster for larger boards.  For smaller stuff, I prefer hand soldering.

[muddyfox]

I can say that I absolutely detest the Kester 951 noclean flux, but that is just my opinion.  I FAR prefer the Kester 186 RMA flux.

Hey, an opinion just as valid (perhaps even more so) than any other! Having never used flux pen, 951 was my best guess.
Having no access to flux cleaners over here (IPA is still debatable, I'm having an argument with the local pharmacy that I'm not likely to win), why would I choose 186 over 951 that's supposedly maintenance-free? Take me to school, Pick! 

[pickdropper]

The main reason is that the 186 flux just works better.  I've never found the 951 to be very effective.  It's better than nothing, but the 186 is much better at getting solder to wet nicely.

That said, I like to clean my boards anyway , so there is no real downside to using mildly activated flux for me.  If you would prefer not to wash your boards, then No Clean might be a better option. 

I don't usually like no clean in general, with the exception of boards that go through reflow ovens and cannot be washed.  But that is pretty rare and shouldn't apply to guitar pedals.

[muddyfox]

I see. So if I could score some 70-90% IPA, would that do for cleaning 186?

TBH, I still cringe at the thought of running anything that has to do with electricity through water at any point.  I guess I'm just weird that way...

[pickdropper]

I see. So if I could score some 70-90% IPA, would that do for cleaning 186?

TBH, I still cringe at the thought of running anything that has to do with electricity through water at any point.  I guess I'm just weird that way...

I wouldn't use 70%.  I can get 91% here for about $1 a bottle.  That works, but it will take a while to get all the residue off.  I recommend using a soft toothbrush to help it.

Flux remover is better, but more expensive.

[muddyfox]

Hey whaddyaknow! I just asked around in some real strange places and it seems that I can get IPA
-1L bottle 99,5% IPA for $15 or
-1L bottle 98% IPA for $7

Would that get rid of 186 residue? And at 99,5%, does it even have time to do anything before evaporating? 

[pickdropper]

Hey whaddyaknow! I just asked around in some real strange places and it seems that I can get IPA
-1L bottle 99,5% IPA for $15 or
-1L bottle 98% IPA for $7

Would that get rid of 186 residue? And at 99,5%, does it even have time to do anything before evaporating? 

Both of those will work fine.  I have 99% pure alcohol at work and it works fine as well.

With any of the alcohols, it basically moves the rosin off of the board, so with enough scrubbing it will come clean.

Flux remover is a solvent that dissolves the rosin, so it takes less time, but as I mentioned it is more expensive.

If you don't have access to Flux remover (or want something less expensive), then the alcohols you mentioned are the way to go.

[muddyfox]

Thanks Pick!

I have 186 ordered from China, I'll just try 951 until it gets here... The school of hard knocks, nothing like it!

[wgc]

Agree with all of pick dropper's comments (and that pic at the top looks fun for sure).

I really like the water soluable fluxes but you really need to be sure to clean, and inside a day is best.  Simply wonderful in a production environment with automated cleaners.   But it will corrode over time if you don't clean it.

I use no clean as a hobby builder though, simply because I hate cleaning rosin, and water soluable flux wicks under things like crazy.

Btw No clean can cause problems with passives in high freq rf applications, but that would be a really rare thing in typical guitar applications, failing wireless transmitters.

Anyway, glad to see another person dipping their toe in the water!

[pickdropper]

Interestingly, I'm working with a board at work arhat is RF based and is requires No Clean solder.

The instructions for the board house are "No Clean/ No Wash."  In that case , the cleaning process causes more issues than it fixes, which, as you know, is not usually the case.