So surface mount it is

[phil from seattle]

by the way, the trick to getting temps right is to sense the temperature at the PCB. Lots of reports about burned PCBs where the thermocouple is hanging in the air.  I have a metal plate that the PCB sits on and has the thermocouple directly attached.

[schmitt trigger]

If Sn63 Pb37 solder is employed, its melting point is actually lower: 183C or 361F.

[paulca]

I assume a normal fan oven heats too slowly?

[phil from seattle]

If Sn63 Pb37 solder is employed, its melting point is actually lower: 183C or 361F.

yes, you are right, I'm using lead free.  principal is the same, though.

@paul, I don't bother with a fan (I assume you mean convection) as it works just fine. I'd be concerned about blowing small parts right off the board.

[janoc]

Hotplate/skillet/oven are good but given the mess and the short life/complicated storage of solder paste, I rarely bother. That makes sense only for people populating a lot of boards. For one offs with reasonable amount of components hand soldering is perfectly fine.

Shelf life of the Kester Sn/Pb paste syringe I'm using is at least one year - I've had it that long and don't store it in a fridge though my basement doesn't get very hot. About $15 USD. So not a tragedy if I have to buy one every year.  I do QFN and LGA packages so reflow is my only choice. If you can stick to SOICs, TSSOPs and similar leaded packages then reflow isn't required. Though, there is something very satisfying baking a PCB and watching the components self-align.

You either got lucky or that was a very good paste and the syringe was airtight. Normal shelf life of solder paste is something like 6 months, refrigerated. Possibly even less if you don't buy a syringe but a little dose/bottle because it is more practical for stenciling than syringes - those are rarely airtight and the paste dries out quickly due to large surface area being exposed.

[phil from seattle]

Even if it only keeps for 6 months, I don't see it as a huge cost item. The jars do dry out fast and I like the syringe better. I just squirt out a little paste on the stencil and spread it. Cap is off the syringe for maybe 5 seconds.

[paulca]

I was kinda referring to using my kitchen oven.  Anyway  It just sounds like too much hassle for my needs.

Anyway, my Rolson magnifying visor arrived.  Nice.  With the maximum lenses in I can actually read the SOIC-8 Eproms that arrived.

Of course as is fate's playful little game is, the SOIC-8 chips arrive, but the SSOP-24 adapters arrive.  The SSOP-24 practice ICs and the SOIC-8 adpaters are still in the post.

[janoc]

I was kinda referring to using my kitchen oven.  Anyway  It just sounds like too much hassle for my needs.

Don't. Getting solder paste (even lead-free) near anything used for food is a bad idea.

If you want to do reflow soldering in an oven, get a small electric one or an electric skillet and use them only for this. Both can be  had cheaply.

[paulca]

So after practising with two SOP-8 EEPROMs which handily had test sketches for Arduino on the internet... they both worked, I tried the SSOP-24 chip!

It did not go easily.  I got quite a lot of bridging had to get the solder wick out, but a bit of patience, poking and dabbing and a little dob of flux and ... it WORKS!

Excuse the focus, but my phone camera doesn't like me using a magnifier lens with it.


I also found some surgical alcohol wipes I had lying around which are basically lint free Isopropanol alcohol wipes.  Which allowed me to clean it up a bit.  I discovered that water an an electric toothbrush doesn't work LOL  Poor chip.

[paulca]

A somewhat better shot:

Almost looks like there is too little solder, but I'm fairly certain they are secure and continuity is in order.

[janoc]

Good job! 

Don't worry about bridges - just add more flux and drag the solder away from the chip with a clean tip.

Solder wick is a bit dangerous - if you aren't careful and it sticks to the joint, you could easily tear off a pad or even a pin on your component. Use that only as a last resort when you manage to drop a really big solder blob somewhere.

For cleaning the flux - most fluxes don't really need to be cleaned, except for aesthetic reasons or if you are worried about leakage (not a problem in 99% of cases). If you don't have isopropanol then normal denatured alcohol works fine, it may just leave a bit of white residue, depending on what it was denatured with.

[tautech]

Paulca
The looooong pads on that PCB make soldering a small IC a breeze.
Remember this if/when you get to do a PCB layout !

Altium for example offers 3 standard SMD footprint types for passives; High Density (shortest/smallest), MD and Low density; longest/biggest. For hand soldering I always select the low density footprint.
I also find it useful to print on paper any layout and physically check components fit.

[myf]

Hello,

I want to solder one simple wire on a circuit with small smd.

I'm quite sure I'll break the circuit if I use wire solder and iron solder. I will get a solder bridge or I'll unsolder one small smd component.

I see video about smd soldering but I don't understand what "magic paste" I must buy.

Can I use this one :
https://www.ebay.fr/itm/10ML-Flux-Pen-PCB-Soldering-Reflow-Solder-Tool-Applicator-Brush-Head-No-Clean/282010097209

Or do you propose an other product.

Do I put very few paste on the wire and on the smd contact, and then I put the hot iron solder on it ? Or do you propose an other way ?

Have a nice day !

F. from France

[paulca]

Are you soldering the wire onto the leg of an IC or onto a random location?

Both are possible, though onto the wire of an IC would need very steady hands.

If however you took your wire, put a tiny bit of solder onto your iron tip and touched both to the end of a surface mount resistor with a good bit of flux for a second it would most likely connect fine without disturbing the resistor terribly.

[myf]

Thank you very much for your answer !

I want to solder this wire on a leg of a smd resistor and, at the other end of the wire mount a Dupond isolated connector.

This solder will not be on the leg of a multi-legs IC, nor on the track (or piste) of the PCB. 

Can I only use my solder iron with the previous flux-pen solder (found on ebay at 2eur = USD 2) ? or must I use other products ?

Have a nice day !

F.

[phil from seattle]

I think you are soldering the wire to a resistor that is already soldered onto a PCB. If that is correct then here is how I do it:
- Shape the end of wire to have the most contact area.
- Tin the wire (apply solder to the end of the wire)
- Apply flux to the point where you will solder.
- Place the tinned wire where you want to solder it.
- Put soldering iron on the tinned wire until the solder melts both on the wire and the PCB.

Some things to consider. Solid core wire is easier than multistrand.  But it is stiffer and makes it easy to put stress on the PCB pad. Easy to lift/break the pad so be careful. If you are doing this for testing/debuging/scoping, a different approach is to solder a very short piece of solid core wire and then use a clip to hook up to the short wire.

[paulca]

So things have progressed.

It's still not perfect, but when a practice board or adaptor works after soldering I always feel I'm mastered it, but every time I do a new practice board or adaptor it presents new chalenges and I learn a few things.

I also got an Andostar microscope.  This is my first attempt soldering using only it.  I'm persevering though it seems more difficult than solder with the jewellers visor. at about 20x.  Part of is the lack of distance perception, the larger part is the coordination required.  I'm sure the later is practice, so... I'm persevering to see if it get's easier.

Things tried and lessons learnt as per the video ... bridges don't come out with hot air, but the iron will kill them quick.

[tautech]

Really nice work, thanks for sharing !

Never would I've thought to use paste like that for fear of bridging but I plainly see if you get the bead not too large it works just fine. 

[paulca]

Yea, when you get the bead wrong bridges are  problem, but...it can be extremely satisfying removing the bridges. 



This is removing the bridges on network resistors when I applied a bit too much solder paste.  An experienced solder'er will see ahead of time the build up and the need to clean the tip with a copper ball more often, as you see me doing eventually.   If after each bridge clear I cleaned the iron this would have taken much less time.  It's part about transfer to the iron and part about distributing the extra to the other pins.  Spread it.  If you can't spread, clean the tip and try again.... only them consider solder wick.

With the microscope you can then review for solder balls and poke them away with the tweezers.  Note; they survive an electric tooth brush with iso-propynol!

[FrankE]

SMD is far less faff once one has the equipment tools, consumables, glass and a little practice.

[paulca]

SMD is far less faff once one has the equipment tools, consumables, glass and a little practice.

Glass?

Though totally agree, the right solder, the right heat, flooding things in flux, good magnification all makes a huge difference.   

It seems the rule is... if you have  a problem then more flux and a freshly clean tip.

EDIT: No need for the microscope, though it does make pretty videos.  A jeweller visor is more than enough.

BTW, none of these videos are edited, they are realtime, unedited, that's how long it took me.

[tautech]

SMD is far less faff once one has the equipment tools, consumables, glass and a little practice.

Glass?

Though totally agree, the right solder, the right heat, flooding things in flux, good magnification all makes a huge difference.   

It seems the rule is... if you have  a problem then more flux and a freshly clean tip.

EDIT: No need for the microscope, though it does make pretty videos.  A jeweller visor is more than enough.

BTW, none of these videos are edited, they are realtime, unedited, that's how long it took me.

Bingo !

BTW, what width Hoof tip are you using ?

[paulca]

I think it's 2mm.  It's a TS100 with a TS-BC2 tip.

[FrankE]

SMD is far less faff once one has the equipment tools, consumables, glass and a little practice.

Glass?

.

Microscope, loupes, magnifiers or whatever other lensing arrangements one prefers.

[dkonigs]

Good luck finally getting into SMD! I always used to shy away from SMD myself.  The last time I was doing hobbyist electronics, I'm not sure it was a popular thing for hobbyists yet. A few months ago I did my first big project in ages, and I still went out of my way to avoid SMD completely.

Now, something has changed. Probably the discovery that many modern components are SMD-only, and the eagerness to try something new. So for the project I'm currently working on, I decided to finally go ahead and just embrace SMD everywhere.

My first real attempt at SMD soldering was tacking a VSSOP chip to a breakout board, using a gigantic DeWalt hot air gun. It was only after this that I discovered that chip actually came in a slightly larger package. Doh!

After that, I bought myself a more appropriate hot-air gun (similar-looking to the Atten), which was much easier to use.
Over the course of this project, I've managed to solder a lot of SMD components to various breakout boards. I'm no longer scared of it. Just a pair of good tweezers, 5x and 10x loupes, and the hot air gun. (I should really get myself a microscope at some point too.)

The only time I've really had trouble was when I run across a component whose footprint isn't available in the common catalog of breakout boards. The one I ran into with this was a UFDFN. I eventually found a "close enough" breakout board, but it took a whole evening of attempts to get it contacting all the pins correctly.

Now I'm looking forward to doing full-board reflow for the actual PCB. Will likely use an oven or hotplate of some sort. (Got a ReflowR on-order, hope it eventually ships.)