How do you prototype with small parts? - Page 1
Forum section: electronics / beginners

author: dfmischler
author_rank: Frequent Contributor
timestamp: June 08, 2013, 06:45:40 pm
content: I tried to deadbug a NC7WZ16P6X TinyLogic UHS Dual Buffer and failed pretty badly. This has 6 pins in an SC70 package 1.25 mm wide. Maybe I could have done it when I was twenty years old (I didn't need a magnifier for anything then, but parts were a lot bigger 30 years ago). Is there a reasonable alternative to making a PCB for something this small? I have always sent stuff out for PCB manufacture, but am willing to try toner transfer for something like this. Is there a reasonable way to make my own solder mask, too?

author: croberts
author_rank: Regular Contributor
timestamp: June 08, 2013, 07:03:56 pm
content: First see if the part is available in a DIP package. If not you can try SMD to DIP adapters.Here is one supplier;http://www.proto-advantage.com/store/index.php?cPath=2200&gclid=CJyn1MCS1bcCFYo-Mgod_QMADQ

author: free_electron
author_rank: Super Contributor
timestamp: June 08, 2013, 07:04:13 pm
content: mm sc70 is perfectly doable dead bug style. you just need precisin tweezers, a correctly sized soldering tip and very fine soldering wire , a steady and and a good magnifier

author: croberts
author_rank: Regular Contributor
timestamp: June 08, 2013, 07:11:59 pm
content: A skill and art worth perfecting free-electron. Those adapters aren't cheap. I guess the adapter may be a good choice if the part is one you will use over and over.

author: C
author_rank: Super Contributor
timestamp: June 08, 2013, 08:45:24 pm
content: On trick I saw a long time agoPut a kink in a wire like you sometimes see in resistor leads.Lay the wire across the chip with the kink between the pins on each side of chip.Solder both sides of chip to wire.cut out the kink between the two pins.You now have a small part with long leads.NOTE: it is a good idea to bend the leads to fit what your mounting the chip on before cutting out the kink.The big advantage is that you can use holders to hold the chip an wire in place.You can preset all the wires to make it faster and easer.C

author: croberts
author_rank: Regular Contributor
timestamp: June 08, 2013, 09:18:04 pm
content: Great idea C...I guess the main thing with the really small parts is good lighting, glasses, magnification, etc so you can see the work clearly and the right tools. I have a good pair of non magnetic tweezers I really like for this kind of work.

author: lgbeno
author_rank: Frequent Contributor
timestamp: June 08, 2013, 09:24:06 pm
content: Microscope is essential, if I was doing this dead bug style, I would also use a drop of superglue to hold the chip in place.Use 30 or 32 awg wire max.

author: C
author_rank: Super Contributor
timestamp: June 08, 2013, 10:33:58 pm
content: Two IC sockets up side down in parallel.Drop wires between pinschange space between sockets at one end only.The rotation causes space between wires to decreaseEdit: bend the wires down past sockets and weight of wire keeps kink pointing up.C

author: TerminalJack505
author_rank: Super Contributor
timestamp: June 09, 2013, 04:51:49 am
content: It seems a lot of people are a bit snobbish when it comes to making their own boards but it really comes in handy for cases like this. I can whip-up a small breakout board pretty quick using the toner transfer method. (I have a CNC mill that I use for drilling so that takes a lot of tedium out of the process.) Small breakout boards make good use of what would otherwise be scrap copperclad.I use to buy two versions of components: an SMT version and a through hole version. I'd use the TH version for prototyping on a breadboard. I'm going to start just getting the SMT version from now on and use a breakout board for the prototyping. This should save me some money and time--since I won't need to find components that come in TH versions.

author: dfmischler
author_rank: Frequent Contributor
timestamp: June 10, 2013, 10:32:06 am
content: Quote from: free_electron on June 08, 2013, 07:04:13 pmI did manage to isolate the ground lead and solder it to the ground plane on my first try. And I got the solder bridge off the chip. Any guidance on the size soldering tip and solder diameter (I might have to order them)?I guess I am also wondering what will happen to my fast rise time signals with 30 gauge leads further away from the ground plane than they would be on a PCB. I'll just try to keep everything short, and if the signal doesn't look good then I'll have to make a PCB anyway.

author: miceuz
author_rank: Frequent Contributor
timestamp: June 10, 2013, 06:19:45 pm
content: I've never tried this with SC70, but for so8/sot23 I just cut traces with a sharp knife on a piece of copper clad board, then either do "live routing" and try to optimize other parts, or just leave ground connections alone, cut a square around the chip and solder wires point-to-point.