1 Building MicroPeak Boards
5 Here's the process I'm using to build MicroPeak boards. I build 15
8 1. Apply paste to the boards.
10 1.1 Check the stencil alignment with a board. Somehow, it always
11 moves. Adjust and reaffix as necessary. The stencil is hinged on
12 the side of the board containing the ATtiny85 so that the tiny
13 ATtiny85 pads are the most carefully aligned.
17 1.3 Apply a bead of paste, on the far side of the ATtiny85 CPU. Spread
18 paste with the blade nearly parallel to the board. Then scrape
19 clean with the blade perpendicular to the board.
21 1.4 Clean the stencil every few boards to keep it from sticking to the
26 2.1 Prep parts for five boards. I group them as they'll be installed
27 on the board. There are few enough that it's easy to tell where
30 2.2 Load parts on each board. I do them in this order:
32 1. 100k reset capacitor
33 2. 470 LED current limiting resistor
42 2.3 After five boards are loaded, prep parts for the next five.
46 3.1 Group boards in a 3x5 array in the middle of the griddle
50 3.3 Turn off griddle power. Let it sit for 1 minute
52 3.4 Turn power back on and wait for all parts to reflow
54 3.5 Let it sit for 10 seconds after the last part reflows
58 3.7 Let parts cool on the griddle to below 100C
60 4. Flash and self-test
62 4.1 Connect pogo-pin fixture to power supply and AVR programmer
64 4.2 Turn on power supply
66 4.3 Insert board, run 'make load' to flash. Note that a previously
67 flashed board will need 'make load-slow' to handle the 250kHz
70 4.4 Wait for the flashing to complete. Check for a single orange LED
71 flash which signals self test complete.
73 5. Attach battery holders
75 5.1 Flow a small amount of solder onto the center conductor pad so
76 that it is raised high enough to hit the battery terminal.
78 5.2 Clean the resulting pad with isopropyl alcohol
80 5.3 Take the metal battery holder cage, align to the circuit board and
81 clamp the ATtiny85 end in a vise whose jaws are horizontal. This
82 end has enough board surface on the parts side to allow clamping,
83 especially if you align the bypass cap inside a gap in the vise
86 5.4 Press down on the battery holder so that the exposed terminal
87 makes firm contact with the PCB pad. Solder in place.
91 5.6 With the vise jaws vertical again, place the board in the end of
92 the vise with the remaining battery holder terminal exposed.
96 5.8 Load battery into plastic tray, install in battery holder
100 6.1 Power the board on. Make sure the LED blinks once
102 6.2 Insert into barometric testing chamber (35cc syringe)
104 6.3 Move plunger to 10cc mark. Insert plug
106 6.4 Wait for the altimeter to be ready for boost detect
108 6.5 Increase volume from 10cc to 20cc (halving pressure)
110 6.6 Make sure altimeter registers boost detect by blinking
113 6.7 Wait 2 seconds, then decrease volume back to 10cc
115 6.8 Wait for altimeter to indicate landing by blinking out
118 6.9 Verify that maximum height is approximately 5500m
124 7.1 Cut 1cm x 4cm piece of closed-cell foam
126 7.2 Insert foam into plastic bag
128 7.3 Push foam to bottom of bag with product card
130 7.4 Drop board into bag, move alongside foam
132 7.5 Push air out of bag and seal