Q's on SMD push button and test pins - Page 1
Forum section: electronics / beginners

author: congia
author_rank: Contributor
timestamp: December 27, 2012, 05:01:59 pm
content: For this thread, I have 2 questions. The first one is how can you solder a surface mount push button onto an existing motherboard? I've watched Dave's video on surface mounting but I guess it's different in this case because there's a hole in under a leg of the push button instead of a flat surface, and it's very tiny. This photo is of my really old iPaq pocket pc. After a drop, the push button fell off, and I lost it so I'm looking to short it if possible. I'm looking to keep the device usable, it's been with me for more than 10 years.When I open up electronics to change capacitors, I usually see these tiny round holes connected to pins or just laying there on the PCB. I assume they are test pins. How can they be used? The following photo is an example of the pins I'm referring to.Thanks guys.

author: SeanB
author_rank: Super Contributor
timestamp: December 27, 2012, 05:21:28 pm
content: The switch can be replaced with a similar one, just solder it in using a 0.5mm tip and some o.5mm flux cored solder. Fiddly but doable. the switch probably can be obtained from an online supplier or from eBay, you just need one that fits the layout.The holes are vias to connect through the board or to connect to inner layers of the board, they are often used for testing of the bare pcb, but are actually part of the design to be used as connections.

author: Psi
author_rank: Super Contributor
timestamp: December 27, 2012, 07:01:17 pm
content: Quote from: congia on December 27, 2012, 05:01:59 pmThey're definitely vias, test points normally don't have empty holes.Although, typically a via would be covered in soldermask so it's possible those are both vias and test points.

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 27, 2012, 07:49:43 pm
content: The board certainly has test pins (or better: test points), but they look quite different from the vias:

author: congia
author_rank: Contributor
timestamp: December 28, 2012, 02:44:35 pm
content: Thanks for the help. So vias are used for transferring power and signals between layers, can I use it to determine the pins of the connectors, possibly with a multimeter? I've tried to stick a multimeter probe onto one of these with the other probe connected to ground but there is no change in voltage whatsoever of any vias.

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 28, 2012, 03:21:27 pm
content: I think you have to explain a bit more about what you are trying to do. If the board is not powered on you will not measure any voltage, and even with the board powered on there is not much that a voltmeter can tell you about the functions of the pins.The only thing you could do with a multimeter is finding out where a certain point is connected to, but you will have to use the Ohms function for that, or even better the conductivity function.

author: congia
author_rank: Contributor
timestamp: December 28, 2012, 04:40:29 pm
content: Oh sorry. I'm trying to find the pins of the connector that is providing power to the device it's connecting to. The device is turned on, though I may try again tomorrow.