??? 04/28/12 22:46 Read: times |
#187267 - plating holes Responding to: ???'s previous message |
Hi Mahmood,
The short answer is, no. There is no easy way to do plated through holes. But there are ways it can be done. Obviously you can set up to do electroplating. But if you do you need to know a couple of things. First, you'll need an "activator" to make the holes platable. That's why it's important not to use dull bits that just burn their way through the FR4. You need clean holes for the activator to work. Basically, activator is just carbon particles in liquid. You dip the board in the liguid and squeegee it off the surfaces. As the liquid dries from the holes it leaves behind a layer of carbon which can be plated. The second thing you'll need to know is a technique called reverse pulse plating. Espeially if you have high aspect ratio holes (l >> d), you need to read up on this. Of course, you'll also need to know the various chemistries you'll use, plating solutions, etc., but that stuff is easy enough to find. It happens that, as we speak, I am doing the ground work to start plating my through holes. Since I recently finished building a lamination press and can now produce multi-layer boards, I need to make the change. I've been using a conductive epoxy to "plate" my through holes. It's a paste that you smear over the panel while a vacuum table sucks the paste through the holes. Then you bake the panel at 160°C for a half hour and you've got continuity. The problem is that the paste is very expensive, and it only works well for 2 to 4 layer boards. You might be able to get a 6-layer done, but I wouldn't take any bets. If you're only going to do 2-layer boards this is a good alternative. If you're going to do multi-layer boards, go ahead and set up to electroplate. One more thing. Whether you electroplate or use conductive epoxy, you will need to put a stop, a protective membrane, on the surfaces of your board before you drill the holes. I use a clear plastic that I buy from a library supply store. It comes in rolls 18" wide (just wide enough to cover both sides of my 9" x 12" panels) with adhesive on one side. It's intended to put on the covers of books to protect them. Good luck, Joe |