GoodFET Construction
Necessities
Besides the components listed on the page that corresponds to your particular PCB, there are a number of things you'll want to have on hand before assembling a GoodFET.
| Controlled output soldering station |
| Fine soldering iron tip |
| Water-soluble liquid flux |
| 23 gauge solder |
| Brass sponge |
| Desoldering braid |
| Soldering iron tinner |
| Tweezers |
| Helping hands |
| ESD wristband |
| Sharp, fine knife of some sort |
| Masking tape |
| Multi-meter with an "LED Test" function |
| Isopropyl alcohol |
| Soft toothbrush |
This list isn't meant to be all-inclusive, nor are all of these items necessarily required. This is simply a list of tools that will help with assembling a GoodFET.
Prepare the work area
You'll want a nice, clutter-free work area. You might want to remove all of the surface mount components from their packaging and put them in their own labeled bins for easy access. The trash that accumulates from the packaging will build up quickly as you work on the board. Make sure your soldering iron is in a spot where you won't get it tangled up in anything or accidentally burn something. Be sure you have easy access to your flux, solder, brass sponge, desoldering braid, tweezers, helping hands/magnifier, and soldering iron holder. A little extra lighting goes a long way here, so grab an extra desk lamp or work light if you have one.
Prepare the tools and board
Make sure the PCB you'll be working on is clean and free of oils and dirt (from fingerprints, etc.). 99% isopropyl alcohol will quickly take care of anything that will prevent a good contact between the components and the board. Heat up the soldering iron enough to melt the solder, and make sure the tip is clean and tinned. If this is your first time surface mounting components, this is a good time to become familiar with the methods you'll be using to solder the ICs to the board.
Practice
Once the iron is hot, apply a small amount of flux to a PCB. If you don't have a spare PCB, the USB portion of the GoodFET PCB will work. Cut some desoldering braid (about 6'') and some solder from each of their spools. Heat up the flux (you will it burn) and apply some solder directly to the PCB. Never apply solder directly to the soldering iron. Remove the iron and the solder, then lay the desoldering braid on top of the soldered area. Gently press the tip of the soldering iron over the area that you previously applied the solder. The desoldering braid will heat up (so watch your fingers), and it will begin to melt the solder. The desoldering braid will suck up all but a small amount of the solder you applied to the board.
Soldering the FT232R/FT232RL
The ICs are probably the most intimidating components of the board, but they are the easiest to solder. Place the FT232RL on the board, ensuring the small circle on the chip is in the same corner as the small circle silk-screened on the board (the lower right when viewed from the top with the USB portion pointing to the left). With masking tape, cover half of the IC so that the pins on one side are visible. Align the pins that are still showing and tape the IC to the board. Now, cover the uncovered half with a second piece of masking tape and uncover the first half. Repeat this until you're sure that all of the pins are aligned properly, but leave half of the IC taped to the board. You'll be moving the board around, so be sure it will stay put.
Now, apply flux to the side you'll be soldering. Run your iron across the leads on the board once or twice to get the board hot, then apply solder to the leads while running the iron across. You don't need a whole lot of solder, just enough to make a small contact between the IC and the board. Applying the solder should take less than 5 seconds. If you accidentally bridge some of the pins, don't worry; we'll be applying desoldering braid to the entire side anyway to ensure we haven't bridged anything.
Take the desoldering braid and lay it across the pins of the IC. Gently pin the desoldering braid down with the soldering iron and rub the pins with the desoldering braid. You should be moving the desoldering braid with the iron, so the portion of desoldering braid that is in contact with the board remains hot. You might need to use different areas of the desoldering braid if one becomes saturated with solder. Continue rubbing the board with desoldering braid until the pins are clean. Check to see if any of the pins are bridged from below. If you see blobs of solder underneath the chip, you will have to draw them out with your iron and repeat the desoldering process. To draw out the solder, hold the board so that gravity will pull on the solder as you heat the pins.
Once you've finished that side of the chip, remove the masking tape holding the IC in place. It takes very little solder to hold the chip to the board; you don't have to worry about the chip moving around without the tape. Flux the other side, heat the pins, apply solder, and then clean up with the desoldering braid. You've just surface mounted the first IC! Repeat this process for each of the remaining ICs.
Soldering the components
The 100 Ohm series resistors are probably the easiest components to start with. Place one on the board (they are non-directional, you only need to worry about placing them so each side touches each solder pad). Apply a small amount of flux to the side you will solder first. Like before, you will heat the place that you will apply solder to, and then apply the solder. The component might move around a little as you apply the solder. Using your tweezers or a small knife, move the component back into place, applying heat to the solder with your iron as necessary. Once the part is properly aligned, solder the other side of the component.
The LEDs are the toughest components to solder. It is very important to ensure that they are oriented correctly before you solder them to the board. Some surface mount LEDs have indicators on them to tell you the polarity, but some markings are rather vague. Use the "LED Test" function of a multi-meter to determine the polarity of the LED. Use the circuit diagram for the GoodFET you are soldering to determine the correct orientation, and then solder the component appropriately.
Soldering the headers
Back to through-hole soldering! Break up your headers into two rows of seven. If you have a connector that will accept these headers (an old floppy drive cable will work), plug the headers into that cable. This will ensure the headers will be aligned properly against each other. Flip the board over and guide the rows of headers through the board. Apply a small amount of flux and solder one pin to the board. Flip the board back over and ensure the headers are perpendicular to the board. If they are not, heat the pin that you soldered and move the headers into place. It is very difficult to move the headers once you have soldered more than one pin! Once the headers are aligned properly, solder the rest of the pins to the board.
Add solder to the USB connector
Finally, add a small amount of flux to the USB connector, and add some solder to each of the four pads. You're done soldering your GoodFET!
Clean the board
Use the manufacturer's recommended solvent for the flux you used on the board. A soft toothbrush can help loosen any flux that's hard to remove.
Use the board
Once dry, your GoodFET is ready to use!