How to use SOIC Chips with Prototyping Breadboards using Adafruit DIP Adapters

How To Use SOIC Chips With Prototyping Breadboards Using Adafruit DIP AdaptersSOIC in action - using an Adafruit DIP adapter

My initial introduction into the world of ICs (integrated Circuits) was the trusty MCP23017, mostly because it came as part of the Ciseco Slice of Pi/O board. Since then I’ve continued to use these chips in my projects and feel somewhat comfortable with them. 

The MCP23017 comes in a DIP format (Dual In-line Package) like many other chips, but I hadn’t even considered that there would be other formats to try.

After recently receiving a ProtoLab board from AlienSpec, I noticed a small section in the corner of the board labelled “SOIC” (“Small Outline Integrated Circuit“). After some Googling I soon discovered that this was a smaller format of ICs that offered chips that could operate in a similar way to the MCP23017.

What a find! So, let me take you through SOIC…

What’s the Difference?

I find some things are a lot easier to grasp when you can see them in the flesh. Now you’re all welcome to come round for a cup of tea, but for now let me just show you the difference between my MCP23017 DIP, my new PCA9536D SOIC, and my PCA9536DP TSSOP chips:




Clearly, the DIP is much much bigger. SOIC is usually around 30-50% smaller in terms of surface area, and a whopping 70% smaller in terms of thickness. This allows smaller and lower profile boards to be created.

TSSOP (“Thin-shrink small outline package”) is even more fiddly, being a touch smaller than its SOIC relative. I ordered a TSSOP chip just to see the difference – I don’t think I’ll try and solder one of these using my basic methods!

However, whilst these particular chips might look very different, they pretty much offer the same functionality to us Raspberry Pi people – they’re both port expanders, and both operate via I2C SMBUS – so your code and layout won’t change much.

NOTE: I haven’t figured out the code for this chip yet – so the above statement is currently an assumption at best!!

SOIC vs Breadboard

In terms of breadboard prototyping with these, you’re going to get stuck.

SOIC chip on breadboard

Not a chance – you can’t use SOIC on a normal breadboard

SOIC chips are too small to push into a standard breadboard like you would with the MCP23017, and you’re probably not going to find a smaller breadboard. No, what you need is an adapter, that lets you break out the SOIC legs to DIP format.

SOIC to DIP Adapters

Amazon sell just the thing – SOIC to DIP adapters manufactured by AdaFruit. I don’t need to mention the reputation and quality of AdaFruit’s products.

The adapters come in a set of 6 in a single board, ready for you to snap apart each time you need one. One side has SOIC-14 (14 pin), the other has TSSOP-14 – I’ll try and cover TSSOP in more detail another day.

These adapters have room for anything up to 14-pin chips – there are other options available from Proto-PIC if you’re after something smaller/bigger.

Adafruit SOIC adapters

Adafruit SOIC/TSSOP adapters from Proto-PIC

All you need to do is solder your SOIC component to the adapter, and then add some header pins to the DIP holes to push these into a breadboard. I be using some male headers out of my header grab bag from 4Tronix.

Soldering the SOIC to the Adapter

Soldering SOIC chips looks a lot worse than it actually is. It’s one of those things that you need to take your time with, and can also be corrected if it goes a bit wrong.

I did some research after initially being a bit worried about soldering something so small. There appears to be 2 methods, one where you use liquid flux first (probably the better way), and another where you just secure the chip and go for it… I’m going for the second option, it’s cheaper and seems simpler. Why? – because I’m an Average Man!

1. Secure the chip in place using something like a crocodile clamp or even Blu-Tack. Take note of the position of the white bar print, indicating the top of the chip:

SOIC adapter ready for soldering

Line up the SOIC legs to the pads (fiddly!)

2. Solder a corner pin first, to set the position of the chip. It helps to heat the leg a bit first, but not too long or you risk damaging the IC:

Soldering an SOIC adapter