Soldering paste for SMDs on HASL finished boards

[garvind25]

Hi,

I wanted to know that if I solder SMDs on HASL finish boards, will I need to use SMD solder paste? If so, which type of solder paste pls? Can anyone point me to an example product on any website like ebay etc for a clear understanding pls? I could see a variety of solder paste available with huge pricing difference.

Thanks,
Arvind Gupta

[Joan_Sparky]

If you want to REFLOW solder SMD, then yes, you need solderpaste.
Just search for ‘solder paste’ on ebay/aliexpress - make sure you’re not buying just the ‘flux’ (yellow creamy like stuff).

I’ve only used the blue 50g pots from mechanic so far (still got 1 pot unopened). Not stellar, but does the job for prototyping (keep them in the fridge after opening!). Little coarse and the residue - while being marked as ‘no clean’ - is better cleaned off after the reflow process with Methylated Spirits in an Ultra Sonic Bath (yes, another piece of kit you’re going to want if you go down that path).

Do you have the stencil yet?
Do you have made yourself acustomed with the process?
You got the toaster oven yet?
One that can ramp to 350 deg C within 2-3 minutes?
…

Stencil Manufacturing

Framed: [image] [image] (if you order cheap, you probably get the bottom version) Not Framed: (polymide) [image] (stainless) [image] Applying paste as hobbyist: [image] There is lots of material and guides out there about this. Some/most fabs/aggregators that offer stencils also offer some pcb material that will act as alignment help/spacers round the stencil when you put it onto a flat desk and hold the whole thing together with self adhesive tape. …

Be very careful if you manually reflow anything in the 0.5 mils pin spacing category or below. That’s the range where I start to get problems… example would be something like a SSOP 10 pin with 0.5 pin spacing package.

Oh and your stencils, for manual work… set the solder paste clearance to 0 for a start before you plot & then order the stencil:

[dchisholm]

@garvind25

I wanted to know that if I solder SMDs on HASL finish boards, will I need to use SMD solder paste? If so, which type of solder paste pls? Can anyone point me to an example product on any website like ebay etc for a clear understanding pls? . . .

This is a question where art, craft, finesse, and personal preference come into play. Like @Joan_Sparky said, you can’t do reflow soldering without using solder paste, whether you use a stencil or not. If you try manual soldering with a soldering iron you may or may not use solder paste. A few incarnations ago my employer used an assembler who did excellent SMT work using very fine-gauge wire solder and a soldering iron with a very small chisel-tip (not conical). She insisted on a certain brand of solder, though I don’t recall which brand.

In the last year or so I have probably done about two dozen boards (or partial boards) in a table-top electric skillet. I use Kester EP256 solder paste, in a plastic syringe from www.cmlsupply.com. After 18 months in the bench drawer it’s still usable for the totally manual work and re-work I do, though I can tell it probably wouldn’t work well with a stencil.

@Joan_Sparky

Be very careful if you manually reflow anything in the 0.5 mils pin spacing category or below. That’s the range where I start to get problems… example would be something like a SSOP 10 pin 0.5 pin spacing

I agree: 0.5mm pitch (not 0.5 MILS!) is probably the limit for manual work with consistent results and not much cleanup or re-work. And that will take some practice.

Dale

[garvind25]

OK…lot of new things here. I just wanted solder new SMD ICs on a new PCB. That’s all. So I will re-ask – do I need solder paste for it. And yes, I was planning to do drag soldering to fix the IC (pin pitch – 0.5mm). Do you suppose it can be done using a 20W iron with drag solder tip? My drag soldering inspiring video is here:

HowTo: Drag Soldering Demo

Also, where can I get drag solder tips pls. I searched aliexpress for it but didnt get any. Is it known by some other name?
And one more query. In the video, the person puts a golden coloured liquid on the ic pins. Is that liquid flux or something else. If it is liquid flux, should I go for liquid flux only or a liquid flux pen?

Thanks,
Arvind Gupta

[hermit]

You are getting away from questions associated with KiCAD and more into basic newbie questions. You might find some other forums more helpful for these types of questions.

The forum moderator, @ChrisGammell, suggests this one.

The Contextual Electronics Forums

[Joan_Sparky]

That’s a small chisel tip, nothing special.
And yes, that’s flux from a pen.
If you got all the right stuff (ideal tip, ideal flux pen, ideal solder, steady hand, steely nervers, lovely day, being in a good mood, …) you surely can do it like that.
It’s really artsy and needs lots of flux and experience to get it.

Note that he drags the SIDE of the tip along the pins, that’s due to the heat not being right in the tip… the smaller they get, the more apparent this will become to you if you solder a lot.

Personally I’d use 0.5mm solder wire from a reputable source and a chisel tip instead of the dragging method if this is a one-of.
If I’d do more I’d rather reflow…

PS: and get a microscope (or at least a head magnifier), you’ll need 2.5x or better…

PPS: stuff like this is being discussed in the eevblogforums as well. Example for the microscope…
http://www.eevblog.com/forum/reviews/my-amscope-microscope-camera-experience-microscope-mods/