Howdy all,  

I have a BJ that I received a month or so ago
and am finally getting things in order to build it. As I read through through the manual, it talks about vias, and filling them in. 

My question is, do all of these vias, (such as the inductors) get filled in on all of the kits? I have the cricket20 with the same inductor vias and it didn’t say to fill these in there? 

Any assistance is greatly appreciated. 

Jason WV3V 

I would suggest filling in just the paths that are so indicated in the instructions.

It's a great kit. You'll have fun.


72,
K3RTA

According to the Bayou manual yes. So I was wondering if they all needed to be filled in on all the kits that have them? 

Jason WV3V 

A via connects a PCB trace on one side of the board to a trace on the other side of the board.  As Dave Benson says, they are plated-through, so, unless the instructions tell you to fill them in, there's no need to.  One reason you might be asked to fill some with solder is if a lot of current is expected to flow through them.

72,
John, AA0VE

John and Dave are on the mark.
A "via" is just a plated through hole that joins the top side copper to the bottom side copper.

Sometimes they are used to make transitions along a trace, so that the trace can run along on one side of the board, then duck over or under to the other side, usually when another trace is blocking the way. They are also sprinkled about to join the top and bottom side ground planes together.

Also, any pad where a component is to be installed is also a kind of via, since there is a pad on the top and bottom and they are connected by the through-plating on the sides of the hole. But in the case of component leads the "via" gets filled by default when you poke the wire lead through and solder. The solder wicks into the hole and fills it.

Being a "belt *and* suspenders" sort of guy I suggested in the Bayou Jumper instructions filling in a select few vias because they carry a relatively large amount of current.
In the case of the BJ, something over half an ampere.

For the geometrically inclined... a typical via is 0.020" or 0.025" in diameter, so its circumference is 0.063" to 0.079".
The board is usually 0.062" thick, so a 0.020" via is equivalent to a trace that is 0.063" wide and 0.062" long. In generally accepted PC board design practice, a trace 0.063" wide, made with "1/2 ounce copper" can, at room temperature, safely carry a current of more than 1 ampere, with a less than 10 degree Celsius rise.

BTW - "1/2 ounce copper" means that one square foot of the copper layer would weigh 1/2 ounce. It really is being used as a measure of the thickness of the copper layer. Most of the boards supplied with QRP kits are made with "1 ounce" copper layers. Hefty power supplies often use "2 ounce."

In general, filling vias is not necessary, but on the other hand, there is no harm in filling them (so long as done neatly with no solder splashes or bridges) Some PC board fab houses allow a designer to specify "filled vias" at time of manufacture, usually at extra cost.

lesson over... quiz next time... LOL

73
Jim, N5IB ...

Thanks Jim and all the rest of the replies. Never hurts to ask. 

Jason WV3V