SMT Production, How do you do it?

This is something I’ve been wanting to find out.

How do you do surface mount production? What tools and equipment do you have to do it?

I’m possibly interested for a new product which I want to do for a production run.

Thanks -
Ryan Walmsley

It depends on the quantity and what tools you have or a willing to get.

• I have done it with a good ole’ Hakko iron.
• I’ve also done it with solder paste and this handy tool sold on
  Tindie: https://www.tindie.com/products/Pieco/paste-press/. We used this with a reflow station.
• For small batches we have recently started making our own stencils in house: http://youtu.be/k7ArBZHaNz0 and using a reflow oven.
• Lastly, we spent a ton of time trying various assembly houses and just last week we did a large production run so that we can stop soldering and focus our attention on new products.

Buy a vacuum pen and these: https://www.tindie.com/products/FemtoCow/set-of-7-smd-smt-tape-reel-holders-trays-8mm-12mm-16mm/

Oh yeah!.. I forgot that I used those SMT Trays as well. They are certainly helpful especially when dealing with parts like SOT-23 and other small parts with leads.

I designed and printed my own just because I thought it would be fun. It took me about 3 re-designs before I got it right.

I have also used a pneumatic paste dispenser which had a foot pedal and a timer that dispensed just the right amount of paste. You can get these on amazon and they are sometimes called glue dispensers.

I actually just started venturing into SMT as well. I modified a toaster oven for reflowing.
Video of my build

Also, I used oshstencils.com for my stencil. Super cheap and good quality stencil for about $10 shipped (about 5 days). Worth trying.

I’m new to Tindie; hoping to have my first board for sale shortly as soon as I get my PCBs back from the fab. Cheers!

LJ

Hi,

I mill my PCB’s with the Othermill desktop cnc mill. It will read Eagle brd files. I prototype them that way and then have the option of going to a board house for quantity. I have milled for SOT-23, 0604, SOIC-8, etc. Usually use 16 mill traces. I can do custom board outlines and drills for any through hole connectors, switches, etc. It’s great being able to get a board right away after editing the layout to try out.

The mill uses FR-1 so a reflow station is best. But when I get FR-4 boards made by a board house I can use a toaster oven for reflow.

I also make my own solder stencils. Here is a full write up on the process

One trick is that when I need to cross conductors I’ll use 0 ohm 1206 resistors as jumpers. It works really well. This often saves having to go to 2 layers.

Once and a while I have to rework the solder, and then it’s just a lot of flux and a soldering iron to clean up shorts on pins.

Regards,

-Tom

Wow that mill looks lovely! Unfortunatly way out of my budget.

In the end I went with trusty dip on this solution as it required stability on the product.

still interesting seeing all the different methods!

For prototype work, I have the boards made by OSH Park. For larger production batches, International Circuits for PCBs. I use a cheap toaster oven I bought from Ebay years ago. I made a controller called RefloLeo that controls power to the oven through a relay (Power Switchtail II) according to a specific reflow profile requirement. I Kickstarted the RefloLeo, but no longer sell these. You can build a similar product from an Arduino Leonardo with a thermocouple breakout board, and even use my open source code for this if you want.

RefloLeo:

For stencils, I use a CNC router (Zenbot Mini with Wolfgang Engineering spindle). I mill from 0.003" brass sheets that I buy from McMaster-Carr.

Solder Stencil:

[Album] CNC Solder Paste Stencil

[Album] DIY Solder Stencils

My CNC router:

For solder paste, using lead-free:
Kester Solder Paste, NXG33, No-Clean, SAC305

For hand-soldered parts (lead-free):
Kester Wire Solder, .025", Sn96.5 Ag3 Cu.5, #58/275, 1 lb

These days, I still use this same setup to bake boards for production every week. I can get about a dozen smaller boards in the oven at the same time and bake them. For the relatively low volume, hand assembly works well.

I place every part by hand with tweezers, so I did invest in a good set of ceramic tipped tweezers. I really like these:
http://www.techni-tool.com/758TW268

Hope that helps.

-John

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I use this Mill machine I have customised and worked on to make both prototype PCB and small pieces for hardware building. The resolution is the same of your device and obviously I use the same technique to make PCB (I have saw your well explained full process page).

My problem making SMD PCB (with a more consistent quantity of components than a couple of stupid resistors, I mean something your PCB example, is that when I mill the tracks if these are too thick the copper tend to detach from the support. Maybe I am milling at a too high speed? At the moment I limit the prototypes to 90% of DIL components avoiding when possible the SMD components.

I have pretty good luck with my CNC router in making surface mount boards. Generally, I run with a 45 degree end mill that has a fairly sharp point at 0.001 inches wide. As for speed, I run at between 5 and 8 inches per minute. I can mill traces down to around 8 mil. The router runs at about 23,000 RPM. Is this similar to how you make boards with your CNC?

-John

As for as I read, as the methodology is essentially the same I suppose that my wrong behaviour is that I move the machine at a too hight speed. Asap I will try with a circuit, making thinner wires but with a slower movement. This is the only thing that I do. Probably I work at too fast speed. Then i keep you updated on the results.

I still have 3 P&P machines laying around in the UK because I don’t have space here in Switzerland to use them

For my prototypes that I don’t ship this is my procedure. (for all my stuff shipped, I find a high quality board house and assembler to do it right)

PCB from osh park
stencil from osh stencil
solder paste the board, and put the parts down.
On the gas stove using a cast iron pan I cook the boards. I watch the pcb and look for the solder to reflow, then quickly move the pan off the heat. Let it cool for 5 min, then pull it off.
Inspect the PCB, then fire it up. most of the times there is no touchup needed.

I have re flowed many BGA, QFN, and 0201 parts with this method.

This process is faster than hand soldering, and gets better results than a toaster oven, heat gun, etc.
Tried out solder paste syringes and such, but the solder stencil is so fast and easy.

This video was my inspiration. https://www.youtube.com/watch?v=1xNSMTWhEvg

Our SMT process is pretty basic and similar to others in this thread:

• Quality PCBs from fab house
• Solder stencil from OSHStencils
• Manual placement
• Oven reflow
• Manual through-hole soldering
• Test (every board!)

I definitely recommend solder stencils over dispensing. OSH Stencils has made them so cheap that there is just no contest - it take seconds to stencil a board and the results are consistent.

Our boards typically don’t have that many parts and we use 0402 at the smallest. Since we do small batches and invest in good tools, a manual process is still cost-effective.

There is a company that does small run SMD assembly. You can find out more here : http://www.smallbatchassembly.com/

I’ve read good things about them on Twitter, but have not used them myself.

-Louis

Hi…i am a new user here. Also i am new to PCB production and learning the all fundamentals related to it. I made a controller called RefloLeo that controls power to the oven through a relay according to a specific reflow profile requirement. I Kickstarted the RefloLeo, but no longer sell these. You can build a similar product from an Arduino Leonardo with a thermocouple breakout board, and even use my open source code for this if you want.

I ended up investing in a professional stencil press, small pick-and-place machine, and commercial IR reflow oven. i do small batch assembly for a number of individuals and companies, with free time on my pnp going to assemble my own products… if you have something you’d like me to quote feel free to message me!

For prototypes, I just use a soldering iron, plenty of flux, some very fine solder, and solder wick for when I use too much of said very fine solder.

For real production, I get boards made and assembled by MacroFab. They do great work, and even at low quantities their pricing is very reasonable.

Here’s a way to do it in your basement:

• Get your circuit boards manufactured by a quality PCB maker like OSH Park.
• Get laser-cut solder stencils make by a stencil maker like OSH Stencils. Comes with a credit-card style spreader and you can get a set of jigs too.
• Buy a small jar of solder paste (you can find good deals on eBay sometimes). You need the type of solder paste that is designed to be spread on a stencil. I use a Formosa brand lead-free paste. It’s expensive but it lasts a long time. Keep it in the fridge when not in use. If it gets too “dry”, you can dilute it (carefully) with odor-free Mineral Spirits.
• You can put components on the board (after spreading paste), using fine tweezers, or you can buy a small hand-operated vacuum pick and place tool.
• Use a small toaster oven for reflow. Ideally one that has at least two heating elements above and two elements below. You can sort of “eyeball” it using the oven thermostat and keeping an eye on the reflow from the outside with a flashlight. This will probably work ok for smaller boards once you get the hang of it. You can step up by putting an oven thermometer inside the oven or using a reflow oven controller kit, and following the recommended oven reflow temperature profiles.

The most significant step up from this would be a small pick-and-place machine likethe LitePlacer. Beyond that, you’ll want to seek out a professional assembly house. MacroFab is a nice turn-key place that comes to mind.

All in all, it’s not that complicated, and you can get enough experience too have some confidence by playing with it for a week or so.

Hope that helps,

Kevin

I’d suggest using an actual temp indicator rather than a thermostat.
Reason is: Temperature of the air inside the oven is not always the same as temperature of the parts on the board.

I’ve used these guys to get exactly the temperature I wanted. This ensure the parts have been soaked to the right temperature.
http://www.markal.com/temperature-indicators/thermomelt/

Cheers!