Eggtimer Rocketry Flight Computer Manual do Utilizador descarregar pdf (Página 13)

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.

With some PAPER masking tape, tape the left and right edges of the board to your work

surface so it will not move.

__ Locate the 8 square pads with holes in the middle, they are just above and below the

large hole. Fill up the holes with solder, and LIGHTLY tin the pads. There should not be a

solder “bubble” above the pads, but just enough that you can see that it’s tinned. If you get too

much on the pads, use some solder wick to remove the excess.

The reason that we have you do this is because later on you’re going to be turning over the

board and heating up the solder that’s in the holes. When it melts, assuming you get enough

heat on it, it will also melt the tinned solder on the pads, and reflow-solder the board to the

matching square pads on the bottom of the GPS module. This provides a good ground for the

GPS’ antenna, as well as a solid mechanical mounting, so this is an important step.

__ Carefully remove the GPS module from its packing. You will notice that one row of

pads goes all the way up the side, and the other row has a “break” in it. You will also notice

that the GPS module’s pads have a “half moon” in the center of the pads; this is to increase the

solder mounting surface when hand-soldered. You will also notice that there are eight square

pads on the bottom of the GPS module; this is to provide a better ground plane with the PC

board when soldered (more on that later).

__ Cut a piece of PAPER masking tape about ½” wide by 2” long. CAREFULLY lay it

across the top of the GPS module, between the sides that DO NOT have the pads.

__ CAREFULLY place the GPS module on the Eggtimer TRS’s GPS pads, making sure

that the “long” row of pads lines up with the “long” row on the board, and that the “half-

moons” on the GPS module’s pads are centered on the Eggtimer TRS’s pads. With one hand,

hold the module in place, and with the other hand smooth the masking tape down against the

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Eggtimer Rocketry Flight Computer Manual do Utilizador Página 13