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Many problems in populating a PCB can be avoided if a proper sequence is followed. A PCB is like paint-by-numbers, but the order in which you solder parts to the board can make all the difference between a successful build or not. With SMD topology, this is even more important. Practically speaking, with through-hole parts you want to solder the shortest part first, then the next shortest part and so on - until you've soldered in the tallest part last. SMD is similar, but with one exception: multi-pin integrated circuit chips should be soldered first. This is because you need access from many different angles in order to successfully solder all of the pins. In the case of the pupDAC with the four-sided PCM2706/7, it becomes even more important that you solder this chip ahead of anything else on the PCB. That's because you need access to all four sides in order to solder all of the pins.
Finally - one other difference is that many SMD PCB's need parts soldered on both sides. I suppose you could wait until all the parts (SMD & through-hole) on one side (top) are soldered before starting on the second side (bottom). However, I like to solder all the SMD parts on one side, then solder all the SMD parts on the other side. This lets you literally immerse the PCB into high-purity alcohol for easy cleaning, because you still have a realtively flat PCB with no through-hole parts in the way. Don't try this with through-hole parts, because electrolytic capacitors are not truly sealed from complete immersion. Also, keep in mind that some of the latest IC chips are hygroscopic. While normally completely sealed, the cases on the newest chips (such as the pupDAC's opamp) will allow moisture migration. I have not found it to be an issue with the 91% Walmart isopropyl alcohol that I use (less than a dollar a quart). However, you should give your pupDAC several hours to completely dry after rinsing before applying power to it. With those principles in mind, install parts on the pupDAC in the following order:
1. U1 |
