Solder Jumpers using SMD Pads? - Page 1
Forum section: electronics / beginners

author: harnon
author_rank: Regular Contributor
timestamp: February 16, 2012, 11:58:11 pm
content: Hey guys,I'm putting together a little board so I can make simple SMD/SOIC prototypes without making a different board every time... one thought I had was to use 0805 resistor pads as either 0805 components or solder jumpers... the spacing between the two pads is around 25 mil / 0.65mm. What do you guys think, would this work or is the gap too big? Would there be some other issue with this method?I've attached an image of the board so you can have a look... its set up to be used with or without a breadboard.Thanks, Will

author: Jad.z
author_rank: Regular Contributor
timestamp: February 17, 2012, 12:17:26 am
content: 0.65mm Is fine IMO. Usually I go for 1mm.If you are going to solder mask this thing keep the area between the pads clear. Trust me you don't want any solder mask in there

author: harnon
author_rank: Regular Contributor
timestamp: February 17, 2012, 12:19:22 am
content: Thanks - I thought about removing the solder mask, but then not having done too much in the way of SMD soldering yet I wasn't sure what impact that would have if I tried to put an 0805 component on top. Only one way to find out I suppose!

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 17, 2012, 12:48:36 am
content: The pad shape and gap makes quite a difference to how easily links can be made and broken. The optimum shape is a pair of semicircles, as solder blobs like to be circular, but 0805 sized pads with maybe a 25mil gap work OK

author: sacherjj
author_rank: Frequent Contributor
timestamp: February 17, 2012, 03:20:14 am
content: You also can use normal resistor pads and 0 ohm resistors.

author: robrenz
author_rank: Super Contributor
timestamp: February 17, 2012, 04:05:10 am
content: It will probably rarely matter, but many zero ohm resistors specs can be as high as 20 mOhm.

author: harnon
author_rank: Regular Contributor
timestamp: February 17, 2012, 09:04:00 am
content: Quote from: robrenz on February 17, 2012, 04:05:10 amYep - thats 0 ohms +/- 10% right?Its a good idea, but the preference would be to "jumper" without any additional components.Quote from: mikeselectricstuff on February 17, 2012, 12:48:36 amI played around a bit with my own patterns - circle inside an arc - but in the end I want to be able to put an 0805 component there if I need it or just solder over if I don't.I've removed the solder mask from between the pads and I'll see what happens!

author: amyk
author_rank: Super Contributor
timestamp: February 17, 2012, 10:47:23 am
content: Quote from: harnon on February 17, 2012, 09:04:00 amYou mean +10%/-0%Using pads shorted together as jumpers is quite frequently seen on laptop motherboards.

author: ChrisKiwi
author_rank: Contributor
timestamp: February 17, 2012, 11:06:37 am
content: You could use 0R 0805 links. I was working on a board this afternoon that required 2 pads to be linked with solder. The pads were rectangle 1.27mm x .62mm with a .25mm space between pads. This scheme worked well, very easy to bridge the gap with solder. I just tried doing the same with an 0603 footprint (with the solder mask removed between the pads) and it wasn't a very happening thing.

author: metalphreak
author_rank: Frequent Contributor
timestamp: February 17, 2012, 12:23:18 pm
content: Quote from: amyk on February 17, 2012, 10:47:23 am0 ohms +10% (x1.10) is still 0 ohms

author: robrenz
author_rank: Super Contributor
timestamp: February 17, 2012, 12:31:07 pm
content: Quote from: robrenz on February 17, 2012, 04:05:10 amdata sheet shows 20mOhm maximum for 0 Ohmhttp://www.alliedelec.com/images/products/datasheets/bm/DALE/70200976.pdf

author: mobbarley
author_rank: Regular Contributor
timestamp: February 18, 2012, 12:47:17 am
content: I have done exactly that before - except I put a small trace between the pads so that they were connected unless I sliced them with a knife. On boards where there is a solder jumper for setting an option etc, I use a circle split into two pads with ~7 mil gap.

author: harnon
author_rank: Regular Contributor
timestamp: February 18, 2012, 12:54:24 am
content: Quote from: mobbarley on February 18, 2012, 12:47:17 amActually that's also not a bad idea...

author: george graves
author_rank: Super Contributor
timestamp: February 18, 2012, 02:07:27 am
content: Quote from: mobbarley on February 18, 2012, 12:47:17 amI think sparkfun has this in their eagle cad library. Adafruit might have it as well.