A guide to surface mount soldering and assembling the 4017 SMT Digital Logic Clock
Are you new to surface mount soldering? With the right tools it’s not actually that difficult. In the below video I’ll walk you through my techniques for soldering fine pitch surface mount parts, as well as how to assemble your clock.
Tools
I HIGHLY RECOMMEND .3mm 60/40 lead based solder. This is not so easy to find from domestic vendors. It’s very easy to find on eBay or Aliexpress from overseas. I recommend the brand “Mechanic” because you don’t have to buy a 2lb spool. Lead is toxic if ingested, so be careful with it. I have yet to find a lead free solder that flows well enough for easy surface mount soldering.
In addition to .3mm solder, you will need a needle point soldering iron. If you don’t have one, I recommend the Pine Pencil by Pine64. It’s quite a soldering iron in a very small package. Note that it comes with a larger tip, and you’ll need to purchase the fine tip set.
Soldering the clock
There isn’t a particular order that the components need to be soldered, as long as they all get soldered in the right place, in the right orientation. Here are a few things to consider:
- R14 and R15 were erroneously labeled as 302 on the PCB. They should say 3001. Both naming conventions mean the same thing, 3000Ω. Different manufacturers use different naming conventions and I ended up using a different brand because the original one was out of stock.
- You can change the order of the LED’s, but you need to also change the order of the LED’s current limiting resistors. The values of the LED current limiting resistors were carefully chosen so that each of the three colors will appear the same. The Red and Blue LEDs require 3KΩ resistors, and the green requires 5.1KΩ resistors. If you want to change the order of the colors around, you’ll want to look carefully at the schematic below and also change the order of the resistors. If you don’t do this, you’ll probably end up with really bright green LED’s that are hard to look at.
- The integrated circuits look the same from a distance, but they are not the same. Look carefully at the numbers on the outside of the packages. There are 4 different integrated circuits in the kit.
- The LED’s, diodes, zener diodes and electrolytic capacitors are polarity sensitive. The white silkscreen layer on the PCB has some sort of marking that aligns with the component to indicate the polarity.
- The resistors are not polarity sensitive, but they do come in several different values. surface mount resistors have numbers on their case to indicate their values. There is numbers on the circuit board that match the numbers on the resistors.
- The brown ceramic capacitors are not polarity sensitive, but there is 2 different values in the kit and they look identical. Their capacitance will be written on a label stuck to their packaging. Be careful not to mix them up.
- The USB-C connector needs to be soldered from the top, as well as from the bottom of the PCB.
Here’s what you should have in your bag of parts:
