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etching question, holes drilled before or after?

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danrogers

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Hi all, I've heard conflicting reports regarding hole drilling. Some things that i have seen have suggested to drill holes before etching and others to drill after.

My concern with drilling after is that I may tear off some of the tracks, or are the quite hardy and resistant?

cheers!
 
I've always drilled after.

I leave a small hole in the middle of each pad so I don't need to use a centre punch.

I've never had a problem with the copper track ripping.

I use the toner transfer method and I always clean the copper, after drilling and just before soldering.
 
thanks mate, do even the smallest of holes and tracks seem to survive?

fair play on the toner transfer, I cant get it to transfer properly but the press n peel paper works :)
 
I use magazine paper - it works a charm.

The smallest pad I've made is 2mm and the hole was 0.7mm.
 
Yes, FHM should do the trick.

EDIT:
Ordinary printer paper will also work but it won't be as good as glossy magazine paper.
 
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If you use Eagle, you can use the drill aid script to make the drill holes much smaller. It helps centering the bits. I've never lifted a trace by drilling and I always drill after etching.

I think lifted traces are subject to the quality of your PCB material as well. I use a fairly decent name brand, because it happens to be convenient to buy here. That maybe a reason why I haven't had much problem with lifted traces.
 
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For single sided boards I drill after etching. For double sided boards I drill only a few holes beforehand (usually just the vias) that I use to align the two sides and then I drill the rest after etching. I've always been scared that I would damage or scratch the etch resist if I drilled before etching. I have had problems in the past with ripping up traces and pads from drilling but that only happened a few times when I didn't leave a hole in the pad.
 
I've always drilled after etching because of two things.

1. The general opinion was to do it that way....and

2. After etching, there is already a guide 'dimple' for the drill bit to aid in centering on the pad.


I haven't done any double-sided boards yet, but I would envisage that in order to prevent damaging pads/vias on the bottom side of a d/s PCB, it is probably essential to use a brand new sacrificial backing board. One which is already full of holes can likely result in the drill bit being 'punched' through the PCB bottom side and creating pad tear-out/lifting, rather than cutting through cleanly.

EDIT: If anyone is in doubt of the merits of sacrificial backing boards, take a drill and make a hole in a piece of wood simply held in the hand. Next, place the same piece of wood atop another piece of wood that you don't mind destroying and make another hole. Compare the finish on the bottom side where the drill-bit exited the workpiece on both examples. The one with a backing board will always have a cleaner hole.
 
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I drill after etching. I found that drilling before etching leaves a little exposed copper around the holes and when etched the solder has to bridge a greater distance. Even if the gap is 0.002" bigger it makes a difference.
 
Drilling before etching might turn out fatal for the board.

The copper layer within the drill hole will be unprotected, meaning that the etchant can work from the drill hole outwards - underetching the photoresist or whatever etch resistant layer is used.

Even if the center is etched 1/100mm through hole components are hard to solder since there won't be any metallic connection between the pin and the pad - resulting in "jumps" with short life span.

Boncuk
 
Drilling before etching might turn out fatal for the board.

The copper layer within the drill hole will be unprotected, meaning that the etchant can work from the drill hole outwards - underetching the photoresist or whatever etch resistant layer is used.

Even if the center is etched 1/100mm through hole components are hard to solder since there won't be any metallic connection between the pin and the pad - resulting in "jumps" with short life span.

Boncuk
Exactly. Difficult to build, and unreliable thereafter.
 
There's also the risk you could damage the etch resist during drilling, unless you drill before toner transfer or photo resist (whichever method you're using) which would make it pretty hard to get the holes in the right place.
 
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You need to make all tracks as fat as possible.
Thin tracks can sometimes be etched away.

That can happen for two reasons only: leaving the board in the etchant unattended for several hours - result: fully insolated board :D

bad quality etch resist. :(

Boncuk
 
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