Section 1 - Mounting The Gps Module - Eggtimer Rocketry Eggtimer TRS Assembly Manual

and particularly the GPS module, INSPECT YOUR SOLDER JOINTS IMMEDIATELY
AFTER SOLDERING THEM. That's why we recommend having a 10x jeweler's loupe
handy... they work very well for making sure that you have nice shiny solder joints that cover
the pad and the component, and for checking to make sure that you don't have solder bridges.
It's MUCH easier to fix ONE component right after you mess it up than it is to go looking for
the "bad" part when the board doesn't work after you first power it up, and is fully populated.
You will be mounting all of the SMT components first, then the through-hole parts except for
the processor, resonator, and buzzer. This will allow you to test it to make sure the GPS/RF
side is working before you install the processor; without those components, it will behave like
an Eggfinder TX transmitter. If you have an Eggfinder LCD receiver or an Eggfinder RX
receiver on 915 MHz (ID = 0), you should be able to get an NMEA GPS feed.
Once you know that the GPS/RF side is working, you'll finish up the processor side, and you
should have a working Eggtimer TRS Flight Computer.
OK, with all that behind us, let's get started...

Section 1 - Mounting the GPS Module

The very first thing you will be mounting is the Maestro Wireless A2235H GPS module. It's a
square part about 5/8" square and ¼" deep, it is actually a small circuit board with an integral
patch antenna. There are very tiny parts mounted on the board, fortunately you don't need to
worry about any of that, you're just going to solder the GPS' pads onto the Eggtimer TRS
board.
It is CRITICALLY important that you get this part mounted properly, because once you solder
it in it will be impossible to remove it. We're not talking "difficult", we're talking
"impossible". Work slowly and carefully!!!
It is also very important that you do not overheat the GPS module. While it IS designed to be
heated in a commercial SMT reflow oven, it CAN be damaged by overheating. You're not
likely to generate enough heat to damage the module, but you don't want to be taking chances.
The solder joints on the top of the board are primarily electrical connections, the ones on the
bottom of the board provide the main mechanical mounting. While every solder joint is
important, the ones on the bottom are especially so, because they hold the GPS module in place
and provide a good ground path for the GPS patch antenna. If those joints aren't good, it may
be possible for G forces and vibration to break a solder joint.
If you're used to soldering SMT components and using no-clean flux, you may want to use
some on the GPS' pads. Use ONLY a no-clean flux such as Kester 951 or Chip-Quik #xxxx;
do NOT under any circumstances use rosin-core flux! You don't need much; one drop spread
lightly over the pads is enough for the entire GPS module.
Lay the Eggtimer TRS PC board down in front of you with the "ANT" side to the left.
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With some PAPER masking tape, tape the left and right edges of the board to your work
surface so it will not move.