SMT prototyping/DIY reflow ovens

[eoasap]

i use SMD all the time. hand solder everything (qfp80, 603 resisters/caps, etc)

i have never used the toaster oven to solder (i know many have), but i have used it to remove an expensive qfp64 several times. works great! going from memory, most devices can't go higher than 430 F or so. Professional reflow ovens do a preheat/conditioning and then quickly bring everything up to optimal temperature and cool down. you'll want to read up on reflow stages and try to emulate them best you can if you plan on assembling boards that way. For my purposes (just taking stuff off), i preheat to 400F, stick board in for about 30 seconds, then take off my part before it cools down.

Keep in mind you should NEVER use a toaster oven for food after its been used for reflow. Also make sure to do it in a well ventilated area.

i've tried etching my own boards, i was turned off a bit by it for a few reasons:
1) you're dealing with strong acids and bases
2) trace width is higher than many fab houses
3) you still have to manually drill all your own holes/vias which sucks if you have a complicated board (or small vias)
4) no soldermask, so harder to solder high pincount surface mount

i go to pcbfabexpress to get my boards made, i end up with 5 boards for $80 (including shipping), includes soldermask and silkscreen

[sean-h]

I always found the re-flowing bit was the easy bit, getting the correct amount of solder paste on the PCB's is the trick.

In the end I purchased a air driven liquid dispenser:

http://www.intertronics.co.uk/products/cjbe1113.htm

This is great and dispenses the correct amount of solder paste on each pad.
Using it by hand takes a while but rigging it upto a cnc machine works a treat.
I need to update my site with examples of it on a machine when I get time.

After using this I was just using tweezers to place the SMT components, but again plan on using the CNC machine as managed to get a cheap pickup pump on ebay which will do small components.

For re-flowing I purchased a small roaster oven for around £40.00 that goes upto 250c and used this. But again on ebay picked up a small conveyor reflow oven for a couple of hundred pounds which does the correct pre-heat and different heat areas.
Problem is with Lead Free components now becoming the norm apparently you need more heat

As far as making PCB's have manually etched for years and used up plenty of caustic soda and wasted many a PCB board!!!

Best find was replacing the caustic soda with Seno PCB apllicators.
http://www.rapidelectronics.co.uk/rk...9438&XPAGENO=1

I wasted so many PCB's getting the mixture correct using commercial developer products as well as caustic soda LOL!
I have never wasted a PCB with these applicators and it also does not burn your skin off!!

Am trying to perfect milling the PCB's via the CNC machine now to do away with chemicals completley.

Regards

Sean.

[bartman]

I'm struggling with a small project that needs SMD parts as well. Mr. E sent me this link which I think is helpful if you are going to do it by hand:

http://www.infidigm.net/articles/solder/

I make my own boards because I never need the quanity to make it worthwhile to have them done professionally.

I use the laser printer method with the special toner paper then iron it onto my board. Once you do a bit of experimenting to get the iron temps right it makes a fairly clean transfer. Recently I started using the green film that is also made by the same company in addition to the toner transfer and that works very well. Makes nice clean lines and no etching pitting like there is with just the toner being the resist.

Bart

[forgie]

you'll want to read up on reflow stages and try to emulate them best you can if you plan on assembling boards that way.....

Keep in mind you should NEVER use a toaster oven for food after its been used for reflow. Also make sure to do it in a well ventilated area.

Yeah, the Elektor article has a uController based controller which follows a very specifically controller temperature curve. I'll try and rig up something like that I think. PCB manufacture may still be something to 'outsource'. Does anyone know of any cheap PCB fab houses that will send internationally? I'm in Australia, and all of the Australian PCB places have large minimum orders (usually a whole panel, which is about $300 AUD = $220 USD) which isn't practical for the home hobbyist/smaller project.

[eoasap]

batchpcb (sparkfun) has a deal where its a $10 setup fee and then $2.50 sq/in with no minimum requirements. i think its a great deal if you have a small panelization or single, small board you want to test. they also ship internationally. http://www.batchpcb.com/shipping.php

---- quote below from the link above---------------------------
International customers - read very carefully. We have shipped to over 85 countries and growing. We have had a 99% delivery rate with only 2 lost packages to Canada via Airmail. This is not to say it is fast. Some packages took 6+ weeks to arrive at their destination. Customs inspections and ground transport can take time, be patient.

* FedEx International Priority is very expensive ($40+) but is blazingly fast, 3 days usually. Trackable and insured.
* Global Express Mail is expensive ($20-$30) but is also very fast. 3-5 days, trackable, insured.
* Global Priority Mail is cheap ($10-$20) and is reasonably fast. 3-9 days, not trackable, not insured.
* Airmail is dirt cheap ($5-9), but is slow. 4 days and up, not trackable, not insured.

[forgie]

Thanks for the links guys. It looks like I still have many options for cheap PCBs after all, even being down in the other corner of the world!

[DynamoBen]

I etch my own boards, usually because I like to free up a bread board and am too cheap to keep buying dev. boards.

I've found it pretty easy and straight forward. For me it’s harder to create the PCB layout than it is to etch the board. I use the Press-N-Peel sheets, usually purchased through http://www.allelectronics.com/cgi-bi...OARD_KIT_.html. However recently I found out you can get as good or better results, with a magazine. You print the design with a laser printer onto a piece of glossy paper out of a magazine. Place that page onto your board and heat it with an iron (on the highest setting) the design will then affix it self to your board.
http://myweb.cableone.net/wheedal/pcb.htm

I started etching with the kit from Radio Shack but quickly out grew it. I now have a plastic tank with heater and pump.
http://www.circuitspecialists.com/prod.itml/icOid/4231

I use Ammonium Persulphate because it is clear so I can see the progress and can be purchased dry. (easier to store) I also tin my boards with "Liquid Tin." I originally used the stuff you have to put in the oven. It took the better part of an hour and stunk up the house. Liquid Tin takes five minutes, no heat required, very easy.

Finally, I haven't done SMT stuff yet. However the guys at sparkfun.com have done three tutorials on it. These are the techniques they use; my favorite is the skillet which works pretty well.

Enjoy:

http://www.sparkfun.com/commerce/pre...Reflow Skillet
http://www.sparkfun.com/commerce/pre...Reflow Toaster
http://www.sparkfun.com/commerce/pre...p?p=Stenciling