This Instructable contains instructions for assembling and modifying your OSH Park Badge from the 2017 Open Hardware Summit. It is based on my I Can Surface Mount Kit project if you want to try something similar.
Surface mount soldering can be a daunting to a hobbiest, but it can be done, and is actually much easier than it looks. I've designed this project to be a gentle introduction.
This project used "1206" size components which are pretty easy to hand solder, and that is where we'll start. The Attiny microcontroller is an "SOIC" package, which is a bit more of a challenge, but still quite within the abilities of hand soldering with hobby equipment.
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Step 1: Gather the Parts, Tools, and Supplies
It is always frustrating to get half-way through a build and find you are missing something. Open your kit on a clean surface and verify you have the following:
- 1 ea. Perfect Purpble PCB lovingly manufactured in the US by OSH Park
- 1 ea. ATTINY85 microcontroller in an 8-SOIC package
- 1 ea. SMD button
- 1 ea. SMD 20mm Battery holder
- 1 ea. Diffuse Red 1206 LED
- 1 ea. 330 ohm 1206 SMD Resistor
- 1 ea. 0.1 uF 1206 SMD Capacitor
- 1 ea. CR2032 Battery
Tools and Supplies:
For my workshops, I use SparkFun's Beginner's ToolKit which has everything you need except the tweezers. Just to prove it can be done, this project and all the photos are done with the $10 SparkFun iron and lead-free solder!
- Soldering iron.
- Wire nippers (I love Hakko CHP-170s)
- Desoldering braid
Step 2: Resistance Is Futile!
I always like to start with resistors because they have no polarity (you can put them in either direction), they are relatively heat insensitive (you can keep the iron on them longer), and they are also cheap (so you can loose 'em and not cry).
A picture is worth a thousand words, so a video is worth a bit more. Colin from Adafruit has made the best introduction to SMD soldering I found, so check that out first.
With that in mind here are the basic steps that will work each of the parts:
- With your clean, hot iron tip, heat the pad and apply a small amount of solder.
- Holding the resistor over the solder blob, heat both the blob and the end of the resistor, and as the solder melts, position the resistor on the pad and remove the iron.
- After the solder solidifies, heat the other side, adding a bit of solder, until a good connection is made.
- Sit back and rejoice in the glory of your first SMD part!
Step 3: Capacitor
The ceramic 0.1 uF capacitor, like the resistor, does not have a polarity and can go in either direction. Follow the same steps as the resistor.
Step 4: Let There Be Light!
Time to up the ante a bit. The LED has a polarity and must go in the right direction or you will have no light, which will make this project basically worthless. It is also a bit more heat sensitive, so hopefully you've got your confidence with your iron so it will be quick and painless.
Through hold LEDs are easy to figure the polarity out because one leg is longer than the other. With SMD parts, it seems like each manufacture has a different way of identifying the cathode (negative) side, so you may need to look hard at the data sheet. For the Lite-On part, there is a green strip on the cathode side, but it is hard to see unless you hold it at an angle.
It might be easier to determine the polarity by looking at the LED before removing it from the packaging. The cathode is always toward the side with the holes. If all else fails, get your coin cell and some jumper wires and light it up.
Once you figure out the polarity, solder it in place like the resistor and capacitor.
Step 5: Button, Button, Who'se Got the Button . . .
Time to add a button to allow us to provide user input to the circuit.
- Place a solder blog on one pad.
- Hold the button in alignment and heat the pad and leg until the solder flows.
- Tack the opposite leg in position.
- If everything looks good, solder the other two legs in position.
Step 6: Brains!
Time for the hardest part. You are ready. The Attiny has a polarity and will require a sharp eye and a close look at the datasheet. The SOIC package, which stands for "Small Outline Integrated Circuit", has a small circle to indicate Pin 1. If you put it in backwards, it will heat up quickly and release the magic smoke (trust me on this). Also, it is extremely hard to remove and reorient an SMD part once it is place (also trust me on this). On a small project like this, it may be easy to start over (or use a re-flow oven).
- Solder one pad.
- Place component in place, apply heat and solder pin in place.
- Make sure the alignment and positioning is correct. It is quite easy to fix or adjust at this point. Not so much latter.
- Solder a second pad in place.Solder the remaining pad. Solder bridging may occur (solder connects more than one pin) as shown in the pictures. Do fret just yet.
- Use solder wick to remove excess solder.
Again, it doesn't need to be pretty. It just needs to work. Take a close look and fix any bridges or pins that are not connected.
Step 7: Power!
Take a deep breath. The hard part is over. Time to solder the battery holder in place.
- Place a solder blob on one pad.
- Place the holder, careful to note the opening points in the correct orientation.
- Heat the holder and the solder blob until the solder flows.
- This takes significantly more heat than normal components so be patient and watch your fingers!
- Once you have one side in place and aligned, solder the second side in place.
At this point, you can insert your battery, flat side up, and enjoy the illumination of a blinky LED. If it is not blinking, don't give up hope. Take the battery out and go to the next step to see how to trouble shoot.
Step 8: Troubleshooting
If it doesn't work at first, don't loose heart! Here are some things to check:
- Look at your solder joints. Any missing or bridged connections should be fixed.
- Check the orientation of the microcontroller..
- Try a fresh battery, ensuring that the positive side goes away from the PCB
- Use a multi-meter and check the voltage
- Check the orientation of the LED. Remove the coin cell and use two wires to connect it directly to the LED terminals. This will tell you if the LED is in the correct position. If it is not, unsolder it and put it in correctly.
- Here is a good video on how to do it: http://youtu.be/Z38WsZFmq8E
- If all else fails, ask for help. Instructables is a great, positive community and will try and help.
I've tried to make this as easy and fool-proof as possible, but if you are a true beginner, you may need the help of someone more experienced. We create Instructables because we like to share the joy of our hobbies. If you are not successful in building this, you can help me by letting me help you figure out why! We are all learning in one way or another. I'm trying to learn how to make my Instructables better!
Step 9: Clasp
There are a number of ways you can display your new found digital bling. You can put a jump-ring in it and use it as a necklace, or solder a broach clasp to the rectangular pad. The easiest (and cheapest) way is with a tie-tack and clasp.
- Insert the tack from the front, pointing toward the back.
- Solder it in like a through-hole lead.
- It will take a bit more heat and solder than normal.
- Let it cool and inspect your work.
Step 10: Reprogramming
- Download the Arduino Programming Environment.
- Install support for the Attiny 85 from either:
- [File] -> [Examples] -> [Arduino as ISP].
- The positive and negative pads are marked so you can orient the header correctly.
- [Tools] -> [Programmer] -> [Arduino as ISP]
- [Tools] -> [Burn Bootloader]
- [File] -> [Upload using programmer]
The biggest source of errors I get involve not having the pins aligned correctly.