The Mute Audio pupDAC
pupDAC Step-by-Step 2
|6. Apply solder to the TPS's (U2, U4, U5, U8, U10), Charge Pump (U7), and Supervisory Microcontroller (U6) anchor pads -
Except for the microcontroller, U6, place the TPS's and Charge Pump on the board by using the middle pin on the 3-pin side as the anchor pin. As with other SMD parts, apply solder to the middle pad on the 3-pad side. Melt it again, and while melted with your soldering iron applied, use tweezers with your other hand to move the chip into position. When aligned and the middle pin on the three pin side is touching the melted solder, then release the soldering iron and let cool. Then release the chip. Proceed to solder a pin on the opposite side of the chip and you have it anchored. Why the middle pin to start? Because you can't access it very well if you solder the other pins, first.
U4 is shown below, but all the other TPS chips and charge pump chip are similar. Note that depending on which hand you use to hold the soldering iron, you may want to re-position the board - rotating it 90 or 180 degrees, depending on the orientation of the 3-pin side with the middle anchor point.
|7. Complete the soldering for the TPS, Charge Pump, and Microcontroller chips -
Anchor the middle pin of each chip as described above, solder an anchor pin on the opposite side of the chip, then solder the remaining pins. You should be able to solder each pin individually without a problem. However, you may want to "drag and wipe" just to finish off the appearance of each solder joint. Refer to the SMD soldering page for details on the drag and wipe method (only for finishing off the joint in this case).
|8. Solder the clock oscillator chip, X1 -
Warning! Do not apply so much solder to X1's pads so that the solder joint touches X1's metal case top - it will short!!.
|9. Apply solder to "anchor" the remaining SMD parts -
Apply solder to the pads of the SMD capacitors ("C" parts), resistors ("R" parts), and ferrites ("L" parts). Choose your pads for convenience with orienting the PCB and with which hand you use to hold the soldering iron. Others disagree with this method, but I don't worry about the orientation. Instead, try to pick the non-grounded pad in each case. It's the easiest pad to solder and ensures that you get the part placed without having to worry about melting a heat-sinked ground pad. Once the part is down on one side, you can spend as much time as you want getting the remaining grounded pad to melt solder.
|8. Solder the 805 capacitors, first -
These are the smallest parts on the board. Solder them first so that they're not blocked from soldering later on. (All SMD capacitors on the pupDAC happen to be 805-size.)
|9. Solder the 1206 resistors -
Solder with the rating on top. If you're really persnickety (like me), ensure that the ratings are all oriented in the same direction horizontally and vertically.
|10. Solder the 1206 ferrites -
These are relatively large and easy to handle and solder (with tweezers, of course!). Like SMD capacitors, they're not marked. So orientation is not a factor and all ferrites on the pupDAC are the same.
At this point, turn the PCB over in your Helping Hands (or whatever device you're using to hold the PCB). We're going to solder all the SMD parts on the back side of the PCB, now.