3rd unused hole on PCB for THT caps: solder filled for a reason?

[lpc32]

Some boards that use thruhole caps are designed to support alternative cap sizes, like 3.5mm and 5mm lead spacing, and so have holes for both options (one hole is common). It seems usually the unused hole is filled with solder.

Is there a real reason for it being filled, or is it just a side effect of wave soldering?

[Jay_Diddy_B]

Hi,

It is the effect of wave soldering.

Jay_Diddy_B

[lpc32]

Thanks. Speaking of which, why are some test points drilled and some not?

[kayvee]

Generally they are drilled when the same signal needs to go through to the other side of the board, so it just doubles as a via and a test point.  Of course if the signal has no need to be on the other side of the PCB there is no reason to drill it.

Having just said that sometimes they are drilled to allow self centering of test pins onto pads.

If they are drilled and undrilled test points on the same PCB most likely the former reason.

[lpc32]

I mean versus ones that similarly go all the way through, just solder filled. If to help with pin alignment/contact, why not do it all like that?

[gxti]

An undrilled pad takes up room on the top layer. A drilled pad takes up room on every layer.

[miguelvp]

My Cyclone V GX Starter Kit has some via test points for things that are not connected to the FPGA pins in case you want to use them you can add a header on the test points and connect them to GPIO pins if you want that functionality.

One set in particular are the pins that drive the audio part of the HDMI transmitter, so if you want sound via HDMI you have to connect them yourself.

It also comes with an Arduino header and it has 2 extra analog inputs as vias, so you can put a 2 pin header and use them if you wanted to.

[lpc32]

gxti, all the pads I'm talking about are drilled. But some are solder filled and some aren't. (Drill + wave soldering + selective drill + plating?)