reflow pick & place?

[Dicky Mint]

Hi People

I'm doing a project with literally hundreds of 1206 SMD components, all under the control of a PICAXE40X2!

I have decided to invest in a DIY reflow oven!

I'm wondering what is the simplest/cheapest way of manually picking and placing 1206s?

Tweezers? Perhaps a fish tank type suction device? One of those pens that's supposed to pick & place?

I know this post is off topic but could someone with experience help, please?

 

[oracacle]

not had much experience with SMDs, but no matter what option you run you are going to need a mountian of patience and a steady hand, imagine a small slip while putting it in the oven.

 

[srnet]

You can put blobs of paste down, just the right amount mind. Place all the components, being very careful not to knock others out of place, and reflow in an oven, or a griddle etc.

With 1206 being so easy to hand solder I would just solder them all by hand.

The only way using the paste an oven method is worthwhile is if you get a solder mask made, and can apply all the paste in one go.

 

[tony_g]

all my circuits are nothing but smd, i tend to stick with some bent tipped tweezers and occasionally a modified aquarium pump suction tool, or at least until i broke the end piece . but even with a good comfortable pair of tweezers once you get started and get a steady pace going it is actually enjoyable lol

but even with tweezers doing 0805 and sometimes 0603 for led's it is still pretty straightforward and easy as long as you get organised.

i currently use a 1400 watt convection toaster oven, its a new one to eventually convert over to reflow once i get done with other things but it works good for me,
i just sit there with my timer and temp probe and manually adjust it, (and enjoy watching the reflow lol)

for stencils i recycle old soda cans and etch a paste stencil from that, the results are good and effective for putting down a paste layer in next to no time, before i found out how to do that it was a long task with the end of a cut off component leg or toothpick and paste each pad which takes so long but the stencil results are much better and the reflowed solder joints look tidy and proffessional, reflowing double sided is interesting as well but do-able


tony

 

[Dippy]

Gosh, you've moved into the next league for DIY.
For the oven I found one of those 40 quid mini ovens from Currys/Argos fits the bill.
This was after a blog on a PCB assemblers site showed the profile isn't that far out from a proper reflow oven.

But how to place hundreds... phew!
I also use the bent-end fine-point tweezers.
Though I reckon my patience would have run out after the first hundred.
And then you have to hope for a 100% first time soldering session in a DIY oven - so a few practice runs are needed.
Assuming you don't knock the board whilst handling

For that number of components I'd deffo get a stencil made. I wouldn't try and DIY a stencil as you can get good plastic ones for around £15.
Good luck, you must have a lot of patience.

 

[Circuit]

Just one thought on tweezers; make sure that you buy non-magnetic ones. Some of the cheaper tweezers have a high iron content and some iron-containing SMD parts stick infuriatingly to the tips of the tweezers. Of course you can buy plastic tweezers, but I prefer high quality non-magnetic stainless-steel ones. Perhaps I should also mention that I have been caught out professionally when I was working both clinically and in research laboratories with "stainless-steel" tweezers made for surgical purposes that also turned out to be magnetic! Reputable European manufacturers of surgical instruments are much frustrated with many hospitals buying in cheap instruments from Eastern countries; they compete on price and therefore hospital managers buy them, but for the end-user, the surgeon, they are far from what we were accustomed to. The hospital manager cannot see a low quality alloy, only the low price. When it comes to a pair of skilled surgical hands working on a patient the difference becomes quite glaring.

 

[Dicky Mint]

Thanks for your replys and encouragement!

I think I'll invest in a vacuum pump and tips!

Although I'm still a little concerned that 1206 packages will be a little small for even the smallest tip!

Rick

 

[inglewoodpete]

I use bent-tip tweezers and the wife's electric frypan.

I have found that chips with unreachable pads underneath them like the LFCSP_LQ package Eg ADXL335 accelerometer, need their pads pre-tinned with liquid flux and the smallest dab of solder on a fine soldering iron. You don't really get two chances with these tiny chips!

 

[Dippy]

I've never tried IP's wife's frying pan, I'm sure it's excellent
My tweezers are stainless European made, I'm happy to spend the extra few quid to save my sanity.
My bug-bear is if the tip get some paste on it then the tip doesn't let go i.e. more stiction tip-component than component-board.

Let us know how you get on with the vacuum pump. Theoretically it sounds the best way to go but I'm sure the quality varies with priceand many people's target is to buy as cheap as possible.
Again, if your tip gets gummy with paste you'll be spending time poking component to get it off.
So some tissues might be a worthwhile purchase too

 

[Oliverar]

+1 for bent tweezers, although sometimes I use straight ones, for complex packages, as I find them easier to align components in 2 planes.

 

[Dicky Mint]

OK bent tweezers are on the shopping list!

Oh my! The sheer number of exactly positioned LEDs, resistors and transistors is daunting!

I'm into new territory now and I'm feeling my way.

Two sided, SMD, PCB, sent out to manufacture, stencil and lead free solder paste and new reflow oven!

Things could get a little hairy but we'll keep smiling!

Glad of the moral support from the forum!

Rick

 

[tony_g]

its not going to be as bad as it seems, you dont have to worry too much about 100% alignment as the solder will pull the components into place once it reflows.

from experience i learned to redesign my board with pretty much all small components on one side and the bigger on the other, just so i could reflow both sides in the oven, before that i had to do one whole side by hand which was fun lol



back side which gets reflowed first



topside with the 08m2/H bridge and a few small bits gets done last



sadly i now have a very unhealthy addiction to making small smt boards, but its fun lol

 

[Dicky Mint]

me too I often get tempted to go miniature!

By which I mean, mostly, 1206's and SO-8's

Back to work!

Rick

 

[Hemi345]

I agree with Tony about placement. Getting them close is usually good enough for the small parts (resistors and such) since the flowing paste will pull the lighter components into place. Need to be pretty darn close on the heavier components. I used the skillet method on my AXEtimeter and it worked excellent with nearly 30 components on one side. 0805 for caps, resistors, and LEDs and some SC70 and a very tiny packaged RTC.

The most time consuming part, if you don't use a stencil, is dabbing on the paste. 0805 and SO sized components are easy but the tiny pads of the smaller components might take a try or two before you figure out the right amount. But I kinda enjoyed picking and placing the parts once all the solder paste was on.

 

[srnet]

I have tried most of the DIY methods of doing SMT stuff.

Using paste and ovens etc. does have a greater sense of achievement, but manual placement and soldering is quicker.

 

[inglewoodpete]

its not going to be as bad as it seems, you dont have to worry too much about 100% alignment as the solder will pull the components into place once it reflows.

One thing to remember when designing a PCB that you intend to hand-assemble: make sure that you keep via's away from SMD solder pads. As the flux in the solder paste melts, it can flow over neighbouring vias. Occasionally, these unexpectedly fluxed-and-soldered vias 'pull' small components like resistors and capacitors out of alignment and possibly short-circuiting exposed pads on the board.

 

[Dicky Mint]

Thanks that's well worth remembering!

Talking about vias or at least connecting pins that join two layers of a board.

Perhaps called terminal pins

Any ideas where I can purchase a small quantity, a hundred or so, of 0.6mm ones?

I'm using 1mm ones at the moment but would like to move over to 0.6 mm ones in future.

 

[Dippy]

In post#11 you said 2-side PCB sent out to manufacture.
They will plate vias for you so no need for soldering - unless you specify otherwise.
And you can make PTH (plated through hole) via teeny-weeny for a tight board.

 

[tony_g]

as dippy said manufactured boards will have the vias done for you, thats one of the things i love about getting boards done instead of doing them myself.

if you do have to make your own board at some point and need vias i got some from a seller from fleabay, i think in the netherlands, sellers user name villarembrandt and many sizes available, i got 0.4mm from them, it can be a bit fiddly to press them in but handy to have if i need to make a home brew board.


tony

 

[fernando_g]

Even if you have -or believe that you have- excellent eyesight, a pedestal mounted and illuminated magnifying glass is a must, to ensure proper solder joint quality and that no micro-shorts have occurred.

 

[Andres Rodriguez]

Question about the stencils

for stencils i recycle old soda cans and etch a paste stencil from that
tony

What chemical do you use to etch the aluminum material that you get from the soda cans?