At 05:54 PM 8/5/99 -0400, you wrote: >I've done this with a toaster oven. It works but I do a LOT of SMT work--including fine pitch (0.025" stuff) TSOP parts--including PICS. Picked up an air dispenser for solder paste, tried that. Had a professional stencil made for a board--tried that. Consistent reflow was a serious problem. Quantity stuff gets farmed out to the Pro's these days. But for small lots--say ten boards or so, with maybe 50 components in a mix of 1206/0805/SOIC/TSOP, I have finally ended up doing it all by hand. You need--repeat NEED--a couple of things. They cost $$ but will pay for themselves faster than you can ever imagine: First a pair of binocular over the head and eyeglasses magnifiers--Harbo r Freight sells a wonderful set for $5! Two powers via a second flip down lens. $30 for the same thing from any of the tool houses. Don't bother with the fluorescent lights with the big lenses--to cumbersome. Put it on your head and flip down when needed. If you can't see what you are doing....... Second: a GOOD, HOT soldering iron with a small--but not too small--"angled screwdriver" style tip. I used Edsyn's 951SX with the 95 watt heater and tips--and keep it turned all the way up. Third: a source of hot hair in a pencil fine stream. Again, Hakko 851 o r equivalent. Pricey, but will pay for itself in the first few rework jobs you do. Can't emphasize this enough. I got a set of tips, but only use the smallest round one. Lastly: at least one Precista 111SA tweezers. This little guy has an angled tip, with two flat surfaces that are grooved to grab and hold round diodes, chip resistors, and IC's very firmly with lots of control. I think I paid $40 or more for mine. Sorry, but fingers and pliers just won't work for production assembly of really small parts. Also, Pamona makes a neat pair of tweezers with contacts on the ends and test leads. Plug it into your multi-meter and measure voltage drop across chip resistors with one hand. About $15. All of this stuff should be available from Instrument Engineers in San Diego at reasonable prices--Tell Jim Hoffman that Kelly sent you. Here is my procedure for really fine pitch stuff (25 Mil TSOP's): 0. First and Formost: ALL of our boards are made from 185 DegC GETEK material--will take total immersion in liquid solder--and I have yet to blister or otherwise damage a board thermally. Well worth the extra pennies per board. I will never ever have a board made of FR4 again. Also, be sure the board and the chips are DRY--bake out at 50 degC or so overnite--or see manufacturers recommendations. Keep chips in the original paks with dry-rite. Chips absorb moisture and will literally explode with too much heat too fast. 1. Get one of the water soluble flux pens from Mouser, and use it to coat the pads on the PCB. Then using a soldering iron and water soluble flux cored solder, flow solder across the pads. Get a blob on the tip of the iron and just drag it slowly across the pads. This will coat each pad with as much solder as it will hold. The flux keeps it all from bridging across adjacent pads. Takes a bit to get the knack, but is really easy. 2. Flux the pads AGAIN--and the pins of the part. 3. If you have a solder pot--dip the well fluxed leads into the solder and shake off so the leads are tinned as well. This step is optional and works on difficult parts--but can leave all the leads blobbed together if you are not careful. Again--FLUX is the key. Sometimes I have to use Rosin flux here if the leads are dirty or not well tinned to begin with. Clean the Rosin flux off the parts before proceeding! Use chloroform, or if you can find it, a rosin saponifier. Mouser used to sell the stuff, but stopped with the last catalog. 4. Solder opposite corners of the part to the board to ensure alignment in the next step. Flux again. 5. Using a pencil hot air system (mine is a HAKKO 815--about $700 from Fry's) reflow the solder on each side of the chip--2-5 seconds is enough. A slight pressure on the top of the part will let it seat down hard on the PCB. I have also used the bottom of a clothes iron, small electric frying pan or 700-watt lamp with heat reflector. Object is to get the pins and solder hot and melted together as quickly as possible and get off. Be sure to let the Hakko warm up for a few minutes to get maximum heat. {an aside: I believe based on years of practical hands on experience that the hotter the heat source, the faster you get on and off the joint, and the lower the total heat transfer to the component--and the lower the probability of damage. Keeping an iron set just above the melting point of the solder is asking for thermal damage. Also, use the lowest melting point solder possible. i use a Kester Sn63Pb37 organic core solder. If you can get it with 2% silver, the liquidus drops another 5 degrees or so--but I've only seen it in bars} 6. Using a combination of Simple Green and VERY hot water, clean the board. Dry with compressed DRY air. Wash again with denatured alcohol or anhydrous rubbing alcohol (not the cheap stuff at the drug store), and again blow off. Bake dry at 50 degC or so. If you are near Mexico, get Cano Puro (99 % grain alcohol), and you can drink the stuff too--diluted) 7. Result is an extraordinarily professional looking PCB. Leaving flux on the board leads to corrosion and LEAKS. I've seen power consumption on a data logger drop from 35 to 10 uA just by cleaning and drying the board. I have done 100+ 16C57 chips an hour using this technique and a little planning. Larger parts--like SOIC's with pads on 50 mil spacing: Put a dab of solder on the #-1 pad for each chip. (this also provides a visual clue on chip orientation--dot on chip goes to solder blob) Using a pair of tweezers and a solder iron, locate the chip and slide pin one into the molten pool of solder to hold it in place. FLUX all the pins and pads Lay a piece of solder (again, I use the smallest diameter multi-core I can get--about 25 mil) across the ENDS of the pins so it is touch both the pins and the pads along one side of the chip--the side opposite pin 1. Touch the solder with a hot iron at the end of the solder. It will melt onto the pad and pin. Without moving the solder, do the next pin, and the next, till the side is done. Each time you touch, the end of the solder will be perfectly placed for the next joint. Repeat on the other side. And you are done. Clean as above. Two pin and three pin parts--as above. Blob of solder on a pad--melt the solder and slide the correct pin into the solder till the part is located, then get the heat off. Solder the other pins. If you have EVER tried to remove through hole parts, you know what a pain it is. I can get SMT resistors and multi-pin IC's on and OFF a board in seconds with NO damage to the board or part. Won't use through-hole passives or actives any may unless there is duress or SMT parts just aren't available. (pin headers are an exception--where the mechanical support is required for other purposes) Enjoy. Kelly **************************************************************************** ******** All legitimate attachments to this email will be clearly identified in the text. William K. Borsum, P.E. OEM Dataloggers and Instrumentation Systems &