Advise for Difficult SMT soldering

I saw a post on the Dorkbot PDX group in regards to using specialized components to make it easier to solder small SMT parts and keep them in place. I used a simple re-usable method some years ago using only microscope slide cover glass and a little extra solder flux paste.

Microscope slide cover glass comes and various thicknesses from 0.13 to 0.17 mm, and can easily be obtained.

You need to trim away some pieces of the glass and shape them into a size you're comfortable using. I suggest somewhere in the following range:

• Width: 2 to 3.5 mm
• Height: 3 to 5 mm

If you're a big fan of Sir Arthur C. Clark, you want them to be exact 2 x 3 mm parallelograms. That way they'll be full of stars... ;)

When you, or maybe someone more skilled than you, makes the glass tiles. Use them in the following manner:

Apply a copious amount of Flux Paste between pin 1 and 2 and then do the same between the two pins on the opposite side of the part. If it's an 8 pin SMT part, you'd place the second glob of paste between pin 7 and 8. Take a glass tile and stand it on end directly between the solder pads for pin 1 and 2, and with the second glass tile do the same on the other side. Whether you do this with the SMT part in place or not is up to you. The Flux Paste should be cool enough sot it keeps the glass tile standing upright since they're nice and light. With the SMT part in firmly pressed down in place and hugged by the glass tiles, solder the 2 pins farthest from the glass tiles. Remove the glass tiles and put them in place for the next part, not necessarily a multi-pin part as this works for any SMT part so long as you're not soldering too close to the Flux Paste holding the glass tiles as it may melt and the tiles may slip away. Keep the tiles stored in a nice clean safe container, I used a contact lens container that screwed closed for the Left and Right eye side separately. So long as the Flux Paste stayed clean, I left it on and placed them in the Left side as leaving the paste on kept them sticking to the side so they wouldn't move around. If the Flux was dirty I put them in the Right side with some Isopropyl rubbing alcohol I drained as needed and cleaned when I needed them.

>>>Making the Glass Tiles<<< Working with the thin glass to shape them can be a pain and may take a few failures (it's called learning!) before you get it right, but once you have the little tiles made, they come in handy.

You'll need the following:

• Safety Glasses
• Glass Slide Covers - thin enough to easily fit between the pins of the SMT parts you use.
• Masking Tape - If you're thinking Duct/"Duck" Tape is good for this too, NO. I find the Blue Painter's Masking Tape works best. (If you have blue Duct Tape, NO!)
• Glass Cutter (optional if you want to score the glass with a small metal file)
• Wide Nosed Regular Pliers - which has had several layers of Masking Tape applied to both sides of the contact area of the jaw to soften it. It's okay to use Duct/Gaffers Tape for this if you want, Gaffers Tape may be best actually.
• Small Metal File and/or Fine Grit Sandpaper capable of grinding the glass
• A sharp razor blade of some type.
• Additional optional items used for snapping the glass once the scoring is done:
  • Thick Hardbound Book
  • Wire that is about 0.5 mm thick - Use a piano or guitar string or some other type of hard wire you have lying about the place. Make sure you can have it pulled straight and taut if you're using musical wire.
  • A thin piece of bamboo skewer that has had one side sanded flat to keep it from rolling.
  • A thin hard board of some type that has an even straight edge and is at minimum 1.5 mm thick - You can use a hard CD Jewel case if you want.
  • Thick cotton or protective gloves. NOT Fingerless.

Step 1: Tape off the area on the glass slide cover on both sides for the area you will be separating from he main part of the slide. Also tape on both sides the rest of the slide cover. Leave a small exposed area going from one end of the slide to the area where you will score the glass with the file or the glass cutter.

Step 2: Put on the safety glasses and get used to keeping them on for the rest of the process. If they're not comfortable and you may want to take them off, go get a pair that you can wear and forget you have on. You don't want tiny shards of glass in your eyes. The cost of a good pair of safety glasses is far less than an ER bill and the trouble having to deal with it. Paranoia is your friend, listen to it.

Step 3: Put the taped glass slide on a smooth, hard surface you (or whoever may own it) don't mind having it scratched by a file or glass cutter.

If you have a nice hard plastic cutting mat be sure it's not warped and sits very flat on a harder flat clear surface. If the cutting mat has become warped, put it on a cookie sheet (preferably with a piece of thick Real Wool between the cutting mat and the cookie sheet, and old scarf cut to size works nicely. If you're not sure it's wool, trim a piece off and try burning it with a match or lighter and see if it melts, and hold it in some tongs away from your face and fingers.)

Place the cookie sheet, wool & cutting mat into and oven pre-heated to 100 - 130 degrees Fahrenheit, keeping in mind you're doing this at your own risk. Heat them for about 5-8 minutes or until it's soft and is easily. Turn off the oven and take them out and immediately with pot holders in both hands place the cutting mat on the hard surface and cover with the wool and then a bunch of heavy books and let it cool there.

• If you live somewhere where it gets real hot and it's over 90 degrees outside, just chuck the cutting mat on the hood or roof of a car in the direct sunlight for an hour and bring it in to cool on a flat surface to get deformation fixed.

Step 4: Score the glass with the Glass Cutter or the small Metal File from one side of the glass to the other. Don't press too hard. Start by applying no pressure, and then gradually add small amounts of force over time. You may need to practice this and ruin a couple slides. You may consider doing many layers of the Masking Tape on both sides of the cutting area to create a good guide for your cutting tool.

Step 5: (Are you still wearing the Safety Glasses?) Snap the glass along the scored line.

• If you're using a Hard Bound Book: place the longest end, preferably at minimum 4 times the length of the piece you are to snap off, into the middle of the pages with the scored area just up to the edge of the pages. Grip the glass slide firmly, but not too hard, with the Wide Nosed Pliers (lots of tape on both sides of the jaw, remember?), with the pliers pointed at the book. Push down with the pliers pretending the scored area of the slide is the fulcrum point of a lever. The glass should snap clean.
• If you're going to use Wire or Bamboo Skewers: Place it directly under the score-line of the glass make sure the wire/bamboo is fastened securely down and will not roll. Use a bit of Museum/Drafters Putty on either end of the glass where it touches the wire to keep the slide from sliding around. While wearing protective gloves, apply a little force with your fingers on both sides and the glass will break. Not too much force of you'll break the glass in a way you don't want.
• If you want to use a thick plate or CD Jewel Case: While wearing the Protective Gloves, hold down the larger side of the slide covering the slide surface as much as you can on top of the plate with the score at the edge. Depending on the room you have to grip the side you are to break off, grip it with the taped pliers or your gloved fingers (or your taped fingers if they're sufficiently protected) and press down evenly and the glass should snap clean.

Step 6: Once you have a long piece of glass a little bigger than the final width you want, use the razor blade to trim away an thin line of the tape where you want to score the height line. Score and snap the glass as per previous instructions.

Step 7: The exact method is up to you how you achieve it. Use the Small Metal File or Fine Grit Sandpaper to clean up the edges and make them as flat and perpendicular to the face of the glass tile as you can and file way the sharp corners so they're rounded. Don't worry about keeping it shiny and polished, you just need it functional.

Step 8: If your done making the tiles and are not about to start soldering, you can take of the Safety Glasses. Unless you're grabbing your Red Ranger BB-Gun and are about to go do something stupid.

Sorry, no pictures of this right now. I need to make a new set of tiles sometime soon (I've been moving a few times the last 5 years and lost that contact lens container) as I'm about to start working with SMT parts again. So maybe I'll post that as a movie on Vimeo.

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