STEP ONE IN CONSTRUCTION
The two hardest parts to install are the triacs and resistors. I expect that the best sequence is to put all the triacs onto the board, then add in the resistors. The triacs can slide around a bit as I maneuver them into place and might bump into the resistors.
PROCESS
I added a bit of solder onto the large pads before applying the triac. This makes it easier to solder them into place and allows me to see the triac sink slightly as it makes a good bond.
Using tweezers I placed the part in position and held it while applying heat and solder. Once the large heat sink of the triac was bonded to the large pad on the PCB, I soldered the ground and base leads to their small pads to complete installation of that triac.
I intended to have every triac perfectly aligned but no plan survives contact with the enemy, so there is a bit of variation in the placement. A very few are slightly rotated; more often the variation is vertical placement, if you call the side of the triac with two small leads the down side.
 |
| First 96 circuits have triacs and resistors installed |
The resistors were dead easy, even better than expected. I had none pop off the tweezers, none got lost, and they aligned very nicely with minimal work.
 |
| 0603 sized resistor below left triac lead |
FLAWS DISCOVERED ON BOARD
I did discover a few errors on the PCB. Some were silkscreen layer issues - a few triacs still had their ICxxx label displayed and one row of signal names were placed above the lamp socket rather than the signal pin, but those are largely irrelevant. Others were missing connections that I discovered as I carefully checked connectivity after each step of soldering.
I was missing a connection between the gate pad of the Accumulator Register Bit 14 and one of the resistor pads. That was easily corrected with a small jumper. I also missed a connection between the large 'anode' pad for the Customer Engineer 4 triac and the lamp socket pad. This was also corrected with a jumper.
No comments:
Post a Comment