Surface Mount tightfist calling...

Dippy

Moderator
I like to balance my tight-fistedness with laziness ;)
i.e. I'm reluctant to spend hours and gallons of fuel to save a fiver.

For small non-crucial SMT work has anyone experimented with something like this?
http://www.newburyelectronics.co.uk/blog/pcb-assembly/low-cost-smd-lead-free-solder-paste-reflow/

Obv I wouldn't do anything expensive in it, but it looks interesting.
Only 40 nicker.
http://www.argos.co.uk/static/Product/partNumber/4235390.htm#pdpFullProductInformation

... and if it doesn't work you can always put sausages in it.
 

Goeytex

Senior Member
I have used (and still do) a toaster oven controlled by a ramp/soak type PID controller purchased surplus on Ebay for $20. Make sure the oven can be set to activate lower & upper elements at the same time. It took a bit of experimenting to get the temperature profile acceptable. But it works nicely for small boards.

A convection oven will distribute the heat more evenly but may not be compatible with your tight-fistedness.
 

bfgstew

Senior Member
A convection oven will distribute the heat more evenly but may not be compatible with your tight-fistedness.
You can always add a small fan into the oven, fleabay to the rescue..............:rolleyes:
 

Goeytex

Senior Member
You can always add a small fan into the oven, fleabay to the rescue..............:rolleyes:
The fan will have to withstand 260C. I mean you can't just stuff a fan in the oven and expect it to work. The fan motor will need to be external to the heated area of the oven. May not be so simple.
 

Dippy

Moderator
Haha, yes. Well I could get the ex-MIL to breathe on the board but I think that would singe my DIPs.

I'm tempted to get one and experiment. Plus a steak & kidney pie.
I won't bother with fan. Too much hassle to get it right and pukka fan ovens are quite a robust build.

I was looking around for a proper reflow oven and had to sit down when I saw the prices.

Oh yes srnet, I've spent an awful lot of time doing it by hand... that's what has impaired my eyesight.
 

RexLan

Senior Member
I would not get too confused and try to over-think it or make it a big deal. It is VETY simple and works perfectly.

I made about 50 of these ... even did them on both sides - 28x1 Picaxe and a Max 7219 on the back.

I used the solder paste and laid the entire top out then set the over to 400° and put them inside. As soon as the solder gets shinny it is done and it is very easy to see it. Takes just a few minutes. Take it out and let it cool.

Put your other components on the other side and repeat. It takes more heat to re-flow than to initially flow so the front side is not affected.

I have had ZERO failures .......... the oven is also great for heating a good roll or reheating some leftovers like ribs and such.

New_GPXT_3.jpg

New_GPXT.jpg
 

Goeytex

Senior Member
I don't know about in the the UK, but here in the states we have resale shops like GoodWill, and Salvation Army stores. Prices for toaster ovens range from $5 to $20 in my area. Convection ovens are a bit more, like $20 to $50. Wall wart/ cell phone chargers are 50c to $1.
 

John West

Senior Member
We've used one at our Hackerspace clubhouse, made by one of our members, but he added a microcontroller to track the SMT soldering curve. It has worked just fine.
 

rq3

Senior Member
I like to balance my tight-fistedness with laziness ;)
i.e. I'm reluctant to spend hours and gallons of fuel to save a fiver.

For small non-crucial SMT work has anyone experimented with something like this?
http://www.newburyelectronics.co.uk/blog/pcb-assembly/low-cost-smd-lead-free-solder-paste-reflow/

Obv I wouldn't do anything expensive in it, but it looks interesting.
Only 40 nicker.
http://www.argos.co.uk/static/Product/partNumber/4235390.htm#pdpFullProductInformation

... and if it doesn't work you can always put sausages in it.
I use a 1/16 inch thick magnetic stainless steel plate on an induction hobb for short run production work.
Initially "calibrated" with an infrared thermometer, I ramp at setting #4 for one minute to activate flux,
then step to max setting #10 until the solder paste flows. Wait 10 seconds, turn off. Induction response is
almost instantaneous, and the profile is very close to optimum with the thermal lag of the plate.
Double sided boards would be a bit tough.

Rip
 

srnet

Senior Member
Oh yes srnet, I've spent an awful lot of time doing it by hand... that's what has impaired my eyesight.
Well, my eyes are not to good either.

I found the effort of placing just the right amount of paste and then the component, far more taxing.

Although well done the oven approach does look neater, even if it does take longer.
 

John West

Senior Member
The primary difficulty with doing SMT soldering by hand is that more and more components are designed without leads that stick out beyond the edge of the component (or even out *to* the edge of the component.) These components require something like an oven to solder them with, no matter how expert one is with hand-soldering small components.

While a commercial re-flow work station can usually get you by, a second-hand toaster oven and a microcontroller for creating the right oven time/temperature soldering contour is really the best (and also the cheapest) way to go for the hobbyist these days.

That's the easy part. Getting the paste-solder laid down cleanly on the bd pads is the hard part.
 

Dippy

Moderator
Hi, thanks for the replies.

Over the years peering at Forum I've seen some very cunning plans.
But, I wasn't really wanting DIY plans. I haven't really got the spare time any more. Good as they are, I just wanted to know if people had found a cheap out-of-the-box (good enough) solution.

John, just get a nice person to make you a stencil. They're quite cheap. Some warm paste, a warm board, a stencil and sellotape, an old credit card and, bingo, those pesky little blobs of paste stay down a treat. It's only when you get really small that finer stencils (sometimes with trapezoidal holes) are needed. If your board or paste is too cold (or too old) it's bleedin' pointless as the solder behaves as you have described ;)
 

John West

Senior Member
Dippy, the lowest price I've found for a "nice person" here in Boulder, CO, to make a stencil for me is $50, US. Then there's the added cost of the paste-solder. Unless I'm making several identical SMT bds, it's cheaper for me to do hand-soldering of what SMT's I can, or use through-hole components. That's why I haven't bothered building up a toaster-oven SMT PCB oven yet. Melting the paste-solder is the least of the SMT fab problems.
 

Goeytex

Senior Member
I just checked my solder paste in the back of the fridge. It's no good and in the trash. Stuff is expensive. I think I'm with John. The toaster oven will be relegated to heating ribs. And with the the PID Controller I can "ramp, soak, and hold" those babies.

As few boards as I make these days it's just not worth it. 1/8 watt through hole resistors are small enough for most stuff I do anyway. And I can hand solder 805 stuff if I need to. Boards are dirt cheap out if China if I don't need em tomorrow, and if I have to etch a board from time to time, that's ok.
 

tony_g

Senior Member
my old black and decker toaster oven has been used for solder reflow for some time now and works great, i still have to look into converting it to full P.I.D control but for the time being a watchfull eye,timer and cheapo fleabay thermocouple display seem to work ok for me.

i normally go between reflow or hand solder of my smt components but 0603 led's are a little finnicky for me at times.

i did manage to find this interesting way of making paste stencils and it gives pretty good results

http://www.youtube.com/watch?v=JWUJtmgh55M

or alternatively i also found this company in the states that would be reasoanble when you factor in the gbp to usd exchange

http://www.oshstencils.com/
 

tony_g

Senior Member
another useful cheapo smt tool that i also made came from the same guy who did the cheap smt paste stencil, i converted one of my aquarium pumps and it works very well.

sometimes even the finest tipped tweezers slip and i end up with lots of 0805 resistors flying across my desk so i end up using it if i have lots of them to place

http://www.youtube.com/watch?v=YhavXauuWqY
 

Hemi345

Senior Member
I've used the frying pan method for some small one off boards. Soldered an FT230XQ (leadless) and the rest of the supporting components successfully. I agree with the rest that getting the paste put down in the right quantity is the hard part without using a stencil. Medium heat for 5 minutes then high till it flows and done. ;)
 

srnet

Senior Member
The primary difficulty with doing SMT soldering by hand is that more and more components are designed without leads that stick out beyond the edge of the component (or even out *to* the edge of the component.)
True, but sooner or later you will make a mistake and need a rework station to remove the SMT component.

So you buy a rework station for £40.

Then you have a way of soldering those pesky DFNs and the like, whilst still being able to hand solder the rest.
 

MartinM57

Moderator
Stencils - anyone tried http://www.smtstencil.co.uk/ ?

Seems cheap, the enlarged picture at the top left looks sort of OK apart from the 12pin thing and the two connectors on the left side, and just email and paypal details rather than the "comfy-feeling" Contact Us page...
 

Dippy

Moderator
Ah, I'd forgotten the frying pan method. I'll have to do a variation on that as my frying pan is a bit new & expensive.

Oh I've spent many an hour dobbing little dobs of paste on to boards, so yes I know the problems.

But as alluded to above it's those pesky packages with the pads underneath that are a trifly tricky with hand soldering.
And as your boards get smaller
Hence the amateur oven. I just have this gut feeling it would be a better distributed heat than the frying pan i.e. the device bodies get heated too.
Naturally, if it works for you then that's good.

I've seen similar prices for poly stencils and even (small) St/St ones at £80.
I've only ever used Steel ones as the Company was paying.
I must check the hole size limitations.
Thanks to all who replied.
 

tony_g

Senior Member
with my toaster oven to date the smallest non resistor/cap/led components i have done successful reflow on is a 3mm X 3mm qfn 16 switching regulator, with the board sitting mid oven and the heating bars warming from the top and bottom it seems to do a good job, most of the effort seemed to go more into etching that darn paste stencil :p
 

Dippy

Moderator
Ah, DIY stencils.. I've had hit & miss results doing that. I spent so much time faffing about (+materials cost) that I'm happy to pay for a pukka one - but don't let my wallet hear that!

What make of toaster oven do you use? Is it anything like that Cookworks (cheap Chinese) oven I linked on page 1 ?
 

matherp

Senior Member
This firm does stencils at sensible prices http://www.proto-advantage.com/

I bought one of their lqfp100 stencils and it is a thing of beauty. Unfortunately I didn't find paste easy to use and ended up hand soldering with 0.25mm solder but at least the pins were on the outside so I had a choice.
 

Dippy

Moderator
I could see all their stencil kits, but I couldn't see the option of sending them Gerbers/Artwork for the whole board.
I just want to flop it out and squeegee just like screen-prints at school :)
 

tony_g

Senior Member
Ah, DIY stencils.. I've had hit & miss results doing that. I spent so much time faffing about (+materials cost) that I'm happy to pay for a pukka one - but don't let my wallet hear that!

What make of toaster oven do you use? Is it anything like that Cookworks (cheap Chinese) oven I linked on page 1 ?
mine is just a cheap black and decker, about 5-6 years old, they are pretty cheap and abundant out here, often a bargain to be found walking around walmart lol.

as for your stencil needs hippy try uploading your gerbers to oshstencils.com to get a quote, my board design files i uploaded to get price ideas came out between $5-7 depending on size and with the cheap postage of $3.25 usd its still the cheapest i have found bar making your own
 

Dippy

Moderator
Thanks Tony, they look really good.
The 'gallery' shots (assuming they didn't spend hours touching up!) look better than the only local supplier near me in UK .
The prices are excellent.

...and ,even more good news for my wallet. In UK Currys do a similar oven at 25 nicker so I'm off to get it.
I'll buy some cheese and bread too so I can eat whilst soldering.
 

grim_reaper

Senior Member
Dippy, if you mean the LOGIK L18MOV13 one that's on offer, I'd be interested to know how you get along with it.
I looked at it last week and was put off by the (probably wrong) spec. that says 'Maximum microwave power'!
 

Dippy

Moderator
grim, yes that one.
I'd assume it was an error by Currys; they probably got some 12 year old (or Exeter post-grad) to type in the details :)

The front panel layout looks similar to the Cookworks one from Argos; and I reckon you'd struggle to get a 1300W Microwave for 25quid.

If it's rubbish for paste it might be fine for pasties.
Or I could screen-print the front-panel with "SMT reflow digital turbo i-oven quad-core with Bluetooth and WiFi. Accurate to 0.001oC. Made in China." and put it on Ebay for £300.:)

I live in the sticks so ordered it on-line and they are delivering on Friday.
I'll report back after a few experiments.
 

grim_reaper

Senior Member
I told the wife to bring one back when she comes home this afternoon.

Unfortunately, she wants to use it to replace the microwave she managed to fill with burnt, smelly greasy stuff! Just have to make sure I test it for soldering when she's out for the day... lol
 

Dippy

Moderator
Oh well you beat me to it.
Don't forget the sodler paste. I'm going for leaded to start with.

I saw my first long Tin Whisker (not tin of Whiskas) the other day. Quite amazing.
 

beb101

Senior Member
This young woman has a lot of good ideas for DIY PCB making,
http://www.frantone.com/designwritings/design_writings.html

In particular, for hand soldering, a DIY Hold Down Tool for SMD Parts,
http://www.frantone.com/designwritings/design_writings5.html#hold

For hand soldering QFN style parts, I just modify the footprint and extend the pads slightly. First apply flux and the solder will wick to the pad underneath. For thermal pads, use a tiny amount of Arctic Silver and if it is a ground just connect it to a ground pad on the part. It's a bit of a pain to modify parts with Eagle, but this is a viable work-around to hand solder these parts.

For reflowing components with a large thermal mass, reflow these first without any paste on the small parts. Then reflow the small parts. The large parts will stay in place during the second stage.

For cheap rework, use ChipQuik,
http://www.chipquik.com/

I don't think it will work for QFN style parts, but for anything with legs it works exactly as advertised. The $15 kit will probably last forever.
 

Dippy

Moderator
Yes, it looks pretty awful. As you say; too much paste. I can do way better than that without a stencil. I used cocktail sticks and some very fine bent-ended tweezers. The bent tips mean that you can rest the pivot end on the table for stability and press the component down to solder.
Moving up to stencil plus oven (we had a tatty 'proper' one at work) means the board looks like it is made by proper people. Get the pads and stencil right and the components line themselves up in most cases.

I don't mean to sound harsh, but it amazes me what people think is 'good'.
 

grim_reaper

Senior Member
To be fair to the guy on the freetronics site, he did say it was a bit of a mess because he was juggling the camera while doing the demo.

Still, it looks very tricky to get professional looking results. I think I'll build all my prototypes on veroboard to re-learn my through-hole techniques before I get back to trying this new fangled SMD stuff. The wife and kids should have got over the novelty of the toaster oven by then as well...
 

MartinM57

Moderator
Here's, literally 5 minutes work, with a scrap PCB, some chipquick solder paste, a slightly sharpened wooden kebab stick (no cocktail sticks in this house, it seems) and about 5 mins under the current Mrs MartinM57's kitchen grill, set to max, about 40mm from the element, starting from cold until the solder melted and then the tray pulled out to for it all to cool naturally

smd.PNG
yes, the via holes aren't in the middle of the via pads (but close enough, the PCBs work fine)
yes, I know the middle one should be a cap of some strange size but I put a 1206 resistor on it
yes, the top and bottom resisitors have pads for 1206 size but I put 0805 on
yes, the amount of solder is inconsistent - I was trying different amounts to see what was best - bottom right fairly obviously
I probably undercooked it - it didn't get hot enough to pull the components into line (or there wasn't enough paste to get enough surface tension to pull them)

...but it's not too bad for a first attempt in literally 5 minutes.

There was no fancy temperature profile - it just got hotter and hotter until the paste melted.

It does show that the key variable is amount of paste - it's a small amount but not too small - and it needs to be consistent. A stencil or some sort of adjustable constant (tiny) volume syringe pump is probably mandatory to get reliable results

The PCB pads are HASL (google it :)) so the solder on them will contribute to the overall amount of solder on the pads - it's just about enough to tack solder a component on for alignment without using any extra solder at all. If you had plated pads, you would probably need a fraction more paste.

Just need some feedback from Dippy on the Currys oven - PCB reflow good-enough for £25 or relegated (promoted?) to sausages?
 
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