# What are QFN sockets for?

I would like to use a QFN chip but soldering it is difficult as the required tools are unavailable. After searching online, I found that there are sockets available that provide pins for those chips, such as this one .

However I saw on the title that they are called programmable adapters. My question now is, what are the main use of these sockets and can they be used to connect the QFN chip to a breadboard and interface with its pins?

• The bottom pad on QFN is critical for thermal dissipation, so beware that that adapter has no pad soldered to the bottom of the chip, which means that the chip will have a much higher junction-ambient thermal resistance. You could quickly program a chip in the socket and then turn it off, but if the chip is expected to dissipate any appreciable amount of power then it will get much hotter in the socket than soldered down. It may get hot enough to fail. – William Brodie-Tyrrell Jan 5 '16 at 11:56
• To the side of the main discussion: If you're buying on AliX, you should be able to beat $110 for a QFN64 socket, since$110 is the normal 3M price for a single unit through Mouser/Farnell/Digikey. Just for thine information. – Asmyldof Jan 5 '16 at 12:49

What they are referring to is programming programmable parts, like microcontrollers and EPROMs, before the chip is mounted to the board. In these cases, the board doesn't include a means to programming the part or providing access to the programming lines.

You can use these sockets any way you like, but a over $100 each, it won't take many to make a hot air soldering station the cheaper alternative. Then you can solder your own QFN and won't need sockets at all. • Comment re: the hot air station - they're more affordable than ever these days for hobbyists. If you don't mind a chinese clone, can pick up a reasonable digitally controlled station for less than$150. Add a board preheater for another \$60 and you're set. – Peter Jan 5 '16 at 17:24
• It's also worth pointing out that soldering QFNs is much easier than most people expect it to be. I bet the original asker is skeptical that it will be easy, but I'd encourage them to give it a shot. The first 2 or 3 you solder will turn out bad, but it doesn't take long to get the hang of it. – John M Jul 22 '16 at 14:02

They are called programmable adapters because you'll often use them to upload firmware into the chip during development. Since chips may die during development using such an adapter is often easier and cheaper than soldering the QFN.

Regarding soldering: In a pinch you can solder the chips using a bit of solder paste, a hot plate and some of practice. It's easier if you get a solder stencil, but it works fine without it.

For prototyping these adapters may work. Whether they work or not depend on the chips you use. Some high-speed or high precision parts have very strict requirements on how far capacitors and other components are located with respect to the chip. This is usually not a problem if you work with a PCB but the leads from the break-out board to the chip itself may already be longer then allowed.

• +1 for mentioning the stricter requirements on PCB layout for high speed parts. – Lorenzo Donati -- Codidact.com Jan 5 '16 at 11:48

That adaptor doesn't look suitable for breadboard. Plugging it into one looks like it would short out pairs of pins. You could probablly use it on stripboard though with careful track cutting.