The easiest but most expensive way to use SMD devices is to use a socket. See
You can make your own PCB adapters with masks from a laser printer.
If you want to use 100 pin IC with 0.5 mm pitch, you will need SMD pads 0.3 mm wide and an isolation gap of 0.2 mm or 8 mil = 0.008 inch. One dot of a 300 dpi printer is 3.333 mil ; 0.00333 inch or 0.08467 mm. The 0.2 mm isolation gap or track width are only 2.36 dots of a 300 dpi printer and only 4.72 dots of a 600 dpi printer.
The precision of a laser printer is to bad too. Try to print a line of 100 mm length in both directions and measure it with a high precision ruler. You will see errors of about 0.5 mm and these errors are different for both directions. Using InkJet's for photo-resist is generally a better idea than laser printers - the ink on a transparency is a little more opaque than toner on a transparency generally. Some of the newer Epson Stylus inkjets are at 1440dpi, which results in higher accuracy tracks at smaller pitch
SMTs are mounted using: reflow soldering, wave soldering and hand soldering. Reflow soldering is where you screen print solder paste onto the PCB land pads, placing the SMT component on the pad, and passing the assembly thru a reflow oven to melt the solder and produce the solder bond. Wave soldering is where you glue the SMT component onto the bottomside of the PCB and then passing the assembly thru a wave solder to produce the solder connection. Hand soldering is done for small-scale SMT mounting, using good old soldering irons.
According to Karl Lunt:
Several of us in the Seattle Robotics Society have been working with the 68hc12 variants, which use the same lead pitch as these chips. So far, soldering them by hand has been no serious problem, so I thought I'd pass along some observations...You can do this either one of two ways. The first way requires a needle tip on your soldering iron, with the temperature control set to somewhere around 650 degrees. You will also need SMT solder, which is a low melting point solder in VERY fine diameter (as a guess, I'd say about 26 gauge or so).
Start by laying down a thin layer of solder flux on the pads. Place the chip on the pads (watch the alignment!) and gently press it in place. The flux should have just enough "stick" to it to hold the chip. Carefully solder one (and only one!) pin on one corner, then verify the chip's alignment. Now solder one (and only one!) pin on the opposite corner, then verify alignment again. If all is well, carefully solder each pin in order, working your way around the device.
NOTE: DO NOT apply solder to the pin! Use the iron to heat the pad, then flow the barest amount of solder from the pad under the pin. Watch for solder bridges; if you get any, use a very fine solder wick to remove the bridge.
Using this technique, I have soldered probably half a dozen 68hc12s with no failures. I have made a few poor connections that had to be reheated, however. Be sure to buzz out your work by probing with an ohmeter between the chip's pin and the associated pad.
The second method takes more confidence than skill, and is favored by several people in the club. Use a large tip soldering iron, say about 1/8th inch wide or more. Stick the chip onto the layout using the flux technique given above. Tack one lead in place at each of two opposite corners, to hold the chip in position. Coat a fair amount of solder onto the iron's tip then, in one smooth stroke, paint all the leads on one edge by wiping the iron's tip down the length of the chip. Repeat for all four edges.
Our surface-mount tech at work watched a trained assembler paint four 68hc12s onto PCBs in the space of a minute or two. He was stunned at how smooth the job went and what a beautiful job she did. I inspected the boards, and they looked nearly as good as those done by machine, and far better than mine (I use method one above). One of the guys in the club uses a wooden-handled soldering iron from the fifties, with a tip that looks like you could use it for body and fender work, but he does all of his high-pitch chips with it and does beautiful work.
Bottom line: Don't let the high-pitch scare you. You might want to practice on some junk PCBs to get started, but this type of solder work is well within the abilities of most hobbyists.
I work with surface mount components and place them by hand all the time. For higher pin count parts, I would recommend that you use some kind of magnifier to better see what you're doing. A stereo microscope is really the best tool for the job but it's a bit out of reach for most people.To hand solder parts, I use small diameter solder (0.015-0.020"), a small-tip iron, flux from a needle dispenser, solder wick, and tweezers. I wouldn't recommend paste unless you're using a hot air reflow tool. A standard soldering iron will cause the paste to form balls which roll around and could possibly end up underneath the part, shorting things out.
For boards that have already been tinned by the factory, I place a small amount of solder on one pad. Using the tweezers, pick up the part and place it on the board footprint. Check the alignment under the magnifier, then heat the one pad. Recheck the alignment. If the pins aren't lined up on all sides, reheat the pad and reposition the part. When everything is lined up, solder another pad on an opposing side and recheck the alignment. When everything is lined up, solder all of the pins. If you get too much solder on a pad, wick it off with solder wick.
DONT TRY TO SKIP USING FLUX! Apply thick types with a hypodermic syringe and a thick needle or thinner stuff with a brush. The secret to making this work is to use lots of flux. It's what keep the solder preferentially adhering to your PCB pads and IC pins instead of to each other. With thicker pastes, the boiling action can cause small balls of excess solder to fly off or bounce into other areas possibly causing shorts.
Alpha Metals. There were three types of solder and two types of flux that were used most. The solders are classified by the types of flux contained in them. The are SMT Core, Cleanline 7000 (both no-clean), and Pure Core (core flux contains a type of acid - must be cleaned after use). The two types of liquid solder flux are 855 (used with the pure core solder - residue must be removed), and NR200 (can be cleaned or not, depending on application).
Very bright lamp or lighted magnifying lamp. A 10x Hastings triplett is probably the most useful magnifier; 20x is pretty handy as well. If you've got lots of money, buy a Mantis.
Metcal SP200 soldering iron, which is a cheaper unit (around $300) and a "hoof" tip. (see www.metcal.com for an apps note with the "drag solder" style technique).
Use the correct solder temperature. 63/37 solder melts at 361degrees farenheit. You'll use a slightly higher temperature. I found that 400F is perfect. Either:
Use electric skillets for dip (wave) soldering and tin/lead plateing. The basic problem with home plating is that a roundness forms that causes the leads to slip off the pads. You can use wick to remove the the rounded tops. "Mopping" the solder over the board with an iron can result in uneven solder hight which can prevent all the chip leads from contacting the pads. Again, solder wick can remove "bumps"
One problem is that the package picks up moisture and turns to steam if heated rapidly as in wave soldering. This can cause delamination of the plastic from the die or leadframe. I've observed the problem appearing as blown output pins. Smaller packages are rarely a problem. Typically you can pre-bake the chip for 12-24 hours at low enough temperatures to prevent rapid generation of steam (Altera suggests 12hrs at 260F).
Toaster ovens or hardware store hot air guns for smt reflow.
Preheat the board to about 100 C (212 F) with an electric pancake griddle, keeping everything except the area being worked on covered with cardboard to avoid burns. (Commercial hot air soldering equipment uses preheat from 100 to 150 C AFIK) The other reason for preheat is to drastically reduce the amount of time hot air must be applied to complete the soldering operation, significantly reducing thermal stresses.
BTY: You can use hot melt glue guns to make plastic injection molded parts.
I've used several different techniques for removing flat packs, all with varying degrees of success. The most obvious is to use a temperature controlled iron, solder-wick as much solder as you can off the pins, and then heat each pin individually, applying slight force from behind with a very fine dental-type pick until the pin pops free. In most cases you can do a couple of pins at a time, and if you're very careful, you won't lift a trace. It's not very pretty, and the chip is mangled when you're done, but it works in a pinch.Another technique is to take a length of thin guitar string or piano wire and slide it behind and through the pins on one side of the chip. Anchor the string with an alligator clip or hemostats to the board, and then gently pull the free end away from the chip as close to the surface of the board as possible, while heating the pins where the force of the is applied. As the pins begin to come free, move the iron along with the string. It takes a little practice, and it won't work well if there are a lot of tall components around the chip, but in most cases it works great, and because the string is pulling each pin outward, instead of upward, the chances of lifting a trace is very slim. The pins around the chip are left relatively unscathed- I've pulled 84 pin chips from scrap units this way and reused them in emergency situations with no problems.
Getting more expensive, our shop has a special flat-pack desoldering tool that I found doesn't work very well. It has a variety of "tips", shaped like the outlines of popular IC packages. The tip fits over the IC and applies heat to all the pins by contact simultaneously. When the solder is hot enough, the technician pushes a button on the handle that applies suction to the center of the chip. The suction causes the IC to "stick" to the desoldering tip and then the tech lifts the iron and (hopefully) the chip away.
The problem is that the tips are so large that even heating is nearly impossible, and I've had a few cases where traces (several, not just one) got lifted when I thought all the pins were free. Lifting the iron with the chip in it just gives no "feel" for when the pins are free. It also takes a long time to warm up, and requires a lot of tinning to get the tip to work at all.
The latest gadget we are now using is a hot air desoldering station. This is simply the best, fastest, easiest way to remove a flat pack. It has a selection of tips with nozzles that direct hot air around the perimeter of standard chip types. The velocity and temperature of the air are adjustable. After about a 5-minute warm up, the technician holds the tip over but not touching the pins, and in about 5 or 10 seconds, with a slight lift from a dental pick, the chip comes easily free.
Jaws drop when I demonstrate this thing. All pins are heated at the same time, and the solder fully flows, so board damage is nearly impossible. The chip is in perfect shape (with tinned leads!) and can be easily reused. The only thing that can be a problem is the possibility of loosening and blowing away nearby small resistors and capacitors if the velocity of the air is set too high. Turning the velocity down on densely packed boards will minimize it, though. I simply can't say enough about this machine, and I highly recommend it if your shop does a lot of flat packs. The high cost will justify itself in the time saved with this method.
But if funds are tight or the quantity of flat packs is minimal, try the guitar string. I've done many that way with great success. .
See also: