Author Topic: Getting started with SMT soldering  (Read 19829 times)

EloyP

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Re: Getting started with SMT soldering
« Reply #30 on: October 02, 2015, 10:23:33 AM »
Hi WhiteHare,

The Dangerous Prototypes guy did this youtube comparing different fluxes:

He makes it seem as though with a good quality PCB and with a high quality flux, the solder almost automatically flows right where you want it to go.

The flux he appears to love the most is this one:  http://www.newark.com/edsyn/fl22/flux-soldering-syringe-5ml/dp/35M3870?ost=EDSYN+%09FL22++FLUX
which, in addition, claims to be a "No Clean" flux. 

In contrast, he thinks the Kester flux he tested was "worthless."

Thanks for sharing. I monitor daily the Dangerous Prototypes posts but sometimes I'm too busy and can't read everything. I had not seen this particular video.

When I used the Kester flux I thought it was fantastic in terms of helping with the manual soldering process -- I really could notice how solder flowed more easily. The problem came later when everything started to corrode. Perhaps it was me that did not do any cleaning. However, the data sheet says it is Ph-neutral and "no clean" so how would have I known that I was supposed to clean the thing very thoroughly?

Cheers,

Eloy Paris.-

WhiteHare

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Re: Getting started with SMT soldering
« Reply #31 on: October 02, 2015, 05:36:39 PM »
Looking at the datsheet for FL-22, it says:
"Flux residues, which hardly occur when FL 22
FLUTSCHI is carefully applied, usually do not affect
the soldering joint.
Practise has shown that using this flux with its low
solids content usually eliminates the need for washing
the soldered circuit board."

"Usually" is a rather vague.  I guess either experience with it tells you whether it needs washing, or else you wash flux off regardless as a precaution just to be sure.

Is there a flux that's absolutely, positively, "no cleaning" required?  Or is it a unicorn?


Felix

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Re: Getting started with SMT soldering
« Reply #32 on: October 05, 2015, 08:46:09 AM »
I've used the kester pen style liquid flux for hand SMD soldering, it's convenient and it works great. But it requires cleaning.
For the panels I assemble I use a paste that has no clean flux and as you can see from Moteinos and other things I make there is very little flux solids residue left behind. That's why it's branded as no-clean. For general purpose soldering most fluxes will work but usually require some cleaning because when you apply it freely you tend to over use. Most solder wire has a flux core also that should be good enough for soldering through hole and even smd.

perky

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Re: Getting started with SMT soldering
« Reply #33 on: December 02, 2015, 01:23:21 PM »
I'm not sure if this has been mentioned before, but Beta Layout in Ireland do a low cost reflow kit. Interestingly the oven is available separately for only EUR138, but the V2 profile controller costs EUR119 - scope there for a DIY controller I think  ;)  Also their PCB-POOL service supply free stensils with protoype PCBs. The PCBs are not bad either.

http://dangerousprototypes.com/forum/viewtopic.php?f=2&t=4471

raggedyanne

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Re: Getting started with SMT soldering
« Reply #34 on: October 03, 2016, 04:42:28 AM »
Yesterday i soldered 86 smt components & they look perfect  8)

My secret weapon is LOC-TITE thread lock, i placed each resistor 0403 and put a small drop of loc-tite on the side gluing to the board while using my hair dryer to speed things up.
The thread lock glue i used requires +280C for removal.

I did not use solder paste  ;)

perky

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Re: Getting started with SMT soldering
« Reply #35 on: October 03, 2016, 06:53:39 AM »
I'm about to go through some hand building of some prototypes, this idea of using thread lock to hold components down is a very interesting one. Usually I tack one end, solder the other and finally dab with no-clean flux and quickly reflow both ends to clean up both joints. This gives a very clean result but is fiddly, especially when tacking the first pad down as it requires holding the component in place while doing it. I'll give the thread lock a go.
Mark.

WhiteHare

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Re: Getting started with SMT soldering
« Reply #36 on: October 03, 2016, 10:15:26 AM »
For hand soldering, I've found that if I pre-solder one pad before applying the part, then afterward I can position and hold the part down with tweezers (with one hand) and then use a solder pencil (with the other hand) to re=melt the solder on the pad just enough to tack it.  It's best to flux the part before remelting the pad.

Previously I used a trace amount of superglue to hold a part in place.  It does give a little repositioning time and sets pretty fast.

0403 is awfully tiny though.
« Last Edit: October 03, 2016, 10:21:42 AM by WhiteHare »

TomWS

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Re: Getting started with SMT soldering
« Reply #37 on: October 03, 2016, 10:24:56 AM »
A toothpick dab of solder paste works well. Place the dab on one pad, the device next and hold it down with the other end of the toothpick, and toouch the soldering iron tip to the bit of paste sticking out from the device.  Solders immediately and, if you don't jiggle, you've got one end solidly soldered.  Dab the other end and repeat.

Tom

WhiteHare

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Re: Getting started with SMT soldering
« Reply #38 on: October 03, 2016, 10:34:46 AM »
A toothpick dab of solder paste works well. Place the dab on one pad, the device next and hold it down with the other end of the toothpick, and toouch the soldering iron tip to the bit of paste sticking out from the device.  Solders immediately and, if you don't jiggle, you've got one end solidly soldered.  Dab the other end and repeat.

Tom

That sounds like the best way of all!  Thanks for sharing that.

raggedyanne

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Re: Getting started with SMT soldering
« Reply #39 on: October 03, 2016, 11:56:29 PM »
My way i can place the components on many boards & have both hands

WhiteHare

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Re: Getting started with SMT soldering
« Reply #40 on: October 04, 2016, 12:50:34 AM »
My way i can place the components on many boards & have both hands

You may in some sense have both hands, but after placement won't you be then be using those same hands to do the soldering?  i.e. How is your method better than the method Tom uses?

TomWS

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Re: Getting started with SMT soldering
« Reply #41 on: October 04, 2016, 01:17:31 AM »
I only use my method when I have the occasional SMT component to mount, eg a 'tuned' component or a board which only has a few SMT parts.  If I had 'many boards' or 'several SMT components', I'll use a stencil, paste, and my handy dandy reflow 'toaster' oven, which, over time, has become a reliable means to make boards with components down to 0.5mm pitch (eg AM18x5 RTC and various DOF sensors).

Tom

raggedyanne

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Re: Getting started with SMT soldering
« Reply #42 on: October 04, 2016, 05:52:43 AM »
There is no jiggle or wiggle  :P

Felix

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Re: Getting started with SMT soldering
« Reply #43 on: October 04, 2016, 08:14:12 AM »
Before getting a pick and place I have assembled countless SMD-only boards BY HAND, never used any glue. Glue is only needed when you do double side mounting.
Reflow will pull the parts in place as long as your stencil is made right.

This is how I used to do it:

This is how I used to make my stencils:

raggedyanne

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Re: Getting started with SMT soldering
« Reply #44 on: October 06, 2016, 05:10:04 AM »
That was awe inspiring  8)