Zero Insertion Force (ZIF) Sockets for Small Outline IC (SOIC)
ZIF stands for Zero Insertion Force. Check out the wiki entry here. ZIF sockets are commonly used to program microcontrollers or to test ICs. Most are familiar with ZIF sockets for DIP ICs. I’ve always found those to be rather redundant, breadboards worked just fine for me.
Since I started using more surface mount ICs, I tend to buy extras and also a bunch of breakout boards to go with it. That’s because I like to test out whatever new ICs I just bought. There’s no way to do that unless I solder the ICs onto at least a breakout board with header pins so that it’s breadboard friendly.
Well, not anymore. I’ve just bought myself 2 ZIF sockets for small outline ICs (SOIC) from eBay. Some manufacturers call it small outline package (SOP or even just SO) although, that shoud technically be referring to a smaller family of ICs (like SSOP or TSOP). Should have gotten these a long time ago. Would’ve saved me a lot of money and trouble.
The one pictured above is for a 28-pin SOIC. I also got another for 16-pin narrow SOIC. As I’ve mentioned, the sockets were from eBay, shipped from China. Now, I’m not racist here, but we all know a lot of products from China are pretty bad in quality. BUT, YOU GET WHAT YOU PAID FOR! I’m not voicing dissatisfaction here. In fact, I’m pretty happy with what I got for the price I paid. It’s about USD20 for the 28-pin socket and USD10 for the 16-pin narrow version. The sockets by themselves seem to be working great thus far. What I don’t like is the breakout boards that the sockets are soldered to. The quality is horrible and plenty of residue flux around the solder joints. I will definitely desolder the sockets later on and make my own breakout boards.
The pic above is a sequence of shots showing how one of these ZIF sockets work. I’d never actually seen one of these in person before and I really didn’t have any idea how it works before I received them. Info was scarce on eBay listings but you don’t have to be a “rocket scientist” (why do people always say that??) to figure out how to use the sockets. All you have to do is push down on the top-half of the socket. When you do this, all the contacts move upwards and outwards. While keeping it pressed down, place your SOIC in. Make sure the SOIC sits flush in the recess and the pins are aligned with the contacts. Then, just gently release your hold and the contacts will clamp down on the pins.
Since each of the contacts individually clamp down on the respective pin, the socket can cope with variations in the dimensions or imperfections of the SOIC. Better yet, this allows one to use the 28-pin socket for a SOIC with fewer pins. With a SOIC of the same pin count, you can just drop it into the socket, no effort is required for alignment. To easily align a SOIC with fewer pins, just slide it to either end.
As far as I am aware of, the maximum number of pins a SOIC can have is 28 (correct me if I’m wrong). Great! That means one of these sockets is all one ever needs right? WRONG! As with DIL or DIP, the width of SOIC is not constant across all pin counts. I learned this the hard way. I was aware that normal DIP ICs are wider for higher pin counts, but I stupidly assumed this wasn’t the case for SOICs. That’s probably because all the SOICs I use thus far have more than 16 pins. As with 28-pin DIP ICs, 16-pin SOICs come in narrow and wide versions. ICs with fewer pins than those number will be narrow respectively and vice versa.
So, I redesigned my driver board for my RGB matrix using some 16-pin SOICs. I placed my order at BatchPCB and simultaneously ordered the parts that I will be needing. A few days later, I got my components and you can imagine how stupid I felt when the 16-pin SOICs I got was narrower than the SOICs I normally own. I should be receiving my PCBs next week. Guess I might have to solder quite a number of jumpers. I thought of getting replacement SOICs with the same function in a wide package but its pretty rare. The SOIC in the pic above is one such rarity.
Anyways, check out the socket contacts in action in the GIF below.
Next are pics of a 16-pin narrow version of the ZIF socket.
Again, the board is of very bad quality but the socket itself is not bad. The contacts appear to be gold-plated. If you’re tinkering or thinking of venturing into surface mount devices, I highly recommend getting a set of these. SOICs are the giants of the surface-mount-world, so it’s a good start. Next up are Shrink Small Outline Package (SSOP) and similar sockets exist for these. I might get those in the future but I’m tinkering mostly with SOICs at the moment.