Building MicroPeak Boards
			    Keith Packard
			      2013-01-11

Here's the process I'm using to build MicroPeak boards. I build 15
boards at a time.

1. Apply paste to the boards.

	1.1 Check the stencil alignment with a board. Somehow, it always
	    moves. Adjust and reaffix as necessary. The stencil is hinged on
	    the side of the board containing the ATtiny85 so that the tiny
	    ATtiny85 pads are the most carefully aligned.

	1.2 Load a board.

	1.3 Apply a bead of paste, on the far side of the ATtiny85 CPU. Spread
	    paste with the blade nearly parallel to the board. Then scrape
	    clean with the blade perpendicular to the board.

	1.4 Clean the stencil every few boards to keep it from sticking to the
	    boards

2. Load boards

	2.1 Prep parts for five boards. I group them as they'll be installed
	    on the board. There are few enough that it's easy to tell where
	    every part goes.

	2.2 Load parts on each board. I do them in this order:

		1. 100k reset capacitor
		2. 470 LED current limiting resistor
		3. Power switch
		4. CPU
		5. CPU bypass cap
		6. LED
		7. baro bypass cap
		8. baro sensor
		9. 4.7k SPI resistor

2.3 After five boards are loaded, prep parts for the next five.

3. Reflow boards

	3.1 Group boards in a 3x5 array in the middle of the griddle

	3.2 Preheat to 100C.

	3.3 Turn off griddle power. Let it sit for 1 minute

	3.4 Turn power back on and wait for all parts to reflow

	3.5 Let it sit for 10 seconds after the last part reflows

	3.6 Turn off power

	3.7 Let parts cool on the griddle to below 100C

4. Flash and self-test

	4.1 Connect pogo-pin fixture to power supply and AVR programmer

	4.2 Turn on power supply

	4.3 Insert board, run 'make load' to flash. Note that a previously
	    flashed board will need 'make load-slow' to handle the 250kHz
	    clock speed.

	4.4 Wait for the flashing to complete. Check for a single orange LED
	    flash which signals self test complete.

5. Attach battery holders

	5.1 Flow a small amount of solder onto the center conductor pad so
	    that it is raised high enough to hit the battery terminal.

	5.2 Clean the resulting pad with isopropyl alcohol
	
	5.3 Take the metal battery holder cage, align to the circuit board and
	    clamp the ATtiny85 end in a vise whose jaws are horizontal. This
	    end has enough board surface on the parts side to allow clamping,
	    especially if you align the bypass cap inside a gap in the vise
	    jaws.

	5.4 Press down on the battery holder so that the exposed terminal
	    makes firm contact with the PCB pad. Solder in place.

	5.5 Remove from vise.

	5.6 With the vise jaws vertical again, place the board in the end of
	    the vise with the remaining battery holder terminal exposed.

	5.7 Solder in place.

	5.8 Load battery into plastic tray, install in battery holder

6. System test

	6.1 Power the board on. Make sure the LED blinks once

	6.2 Insert into barometric testing chamber (35cc syringe)

	6.3 Move plunger to 10cc mark. Insert plug

	6.4 Wait for the altimeter to be ready for boost detect

	6.5 Increase volume from 10cc to 20cc (halving pressure)

	6.6 Make sure altimeter registers boost detect by blinking
	    quickly.

	6.7 Wait 2 seconds, then decrease volume back to 10cc

	6.8 Wait for altimeter to indicate landing by blinking out
	    maximum height

	6.9 Verify that maximum height is approximately 5500m

	6.10 Turn off power

7. Package

	7.1 Cut 1cm x 4cm piece of closed-cell foam

	7.2 Insert foam into plastic bag

	7.3 Push foam to bottom of bag with product card

	7.4 Drop board into bag, move alongside foam

	7.5 Push air out of bag and seal