| edm |
I have just finished my first batch off home brew pcbs and was in the mindnumming stage of drilling. During the 2nd pcb I found out to my disspair that a ring of copper was forming arround the drill, after removing the dust from the sticky flux surface I found out that the ring was formed by solder pads :bawling:.
The solder pads which are most sensative to dissappearing are 1.52 mm in diameter and drilled using a dremel in a stand using a 8mm drill. Is this too big???
I should mention that I have merged the mask and the drill files (I just love postscript :D) so that after etching I have a nice little centre point for drilling.
I have searched the site and found out that some people drilled the holes before etching, is this a better manner? The pro is that you are not likely to tear copper of, but I con is that you do not have the nice centre point.
Since I am asking anyways, anybody with good suggestions for making double sided pcbs. I made mine by using two strips of photosensative material, which are put on two of the corners of the 'target' material. Then I tape the bottom mask to the strips, remove the 'target' and carefully allign the top mask. Then I slide the target in between and expose twice and etch. This works reasonably well but the allignment is not completely perfect.
Since this is just the very first batch of pcbs I made, my experience is limited. Help for both items is appreciated,
Regards Emiel |
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| tiroth |
| Are you using a high speed drill with a sharp carbide bit? I have had no problem with annular ring much smaller than that. I have heard that a bit that is not sharp enough can "pull" the pad off the board, and high speed is also necessary for a clean hole. |
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| edm |
| I use a dremel to drill, that does 30k rpms according to the box. The drills are 'Wolfram-Vanadium-Stahl'. Oh and the drills are not 8mm but 0.8mm. I just bought the drills so they should be sharp, I hope. |
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| tiroth |
Not sure what to tell you. I also use a dremel at perhaps the 70% setting, in the dremel mini drill press.
I generally find it best to leave a solid pad to cut through, although this can make centering the bit a lot harder. |
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| JBL |
Nevr broke a pcb when drilling even with a dremmel or a heavy duty power drill.
(I'm using cheap bit, they d'ont break the pcb but they break themself.)
What's the brand and type of your pcbs? |
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| jackinnj |
| is that the drill collet is not necessarily "true". Unsharp drill points is more likely the problem. You are heating the pad and undoing the adhesive bond. Perhaps a better idea would be to drill before etching. (i.e. after exposure and development.) |
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| haldor |
Hi Emiel,
I tend to leave bigger pads than are really necessary on my DIY boards. I find that not only does it make drilling easier, but the pad is a lot less likely to lift off during soldering. Making plated through holes is possible, but takes a real commitment of money and space.
There are PCB eyelets (like tiny copper gromets) you can buy that will let you replace a missing gromet (I have used these when installing large, heavy or high heat generating components).
Techni-Tool sells a PCB eyelet kit for $200 US. I have seen similar kits for around $60 US, but can't find a link to them right now. Do some searching for PCB eyelet or gromet and you should be able to hunt them down.
Phil |
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| edm |
| quote: | | What's the brand and type of your pcbs? |
I don't know I bought them in a local electronics shop.
| quote: | | is that the drill collet is not necessarily "true" |
I don't know what a 'collet' is and neither does my dictionary, so i don't get what you mean here.
| quote: | | Perhaps a better idea would be to drill before etching. (i.e. after exposure and development.) |
I already thought that this could help, but where is the catch here? I thought that the standard way was to drill after...
I think I am going to try to drill before etching, i think it can also help to get allign my double sided boards better then my current method. (Expose/develop one side, drill, place mask other side expose/develop etch).
| quote: | | I tend to leave bigger pads than are really necessary on my DIY boards. |
I already changed some of the boards to bigger pads, but in one of my pcbs I have a micro controller with a double row of pins so I need to go in between the pads with my traces. So here I cannot make the pads bigger.... When my layout was done, i found out that the microcontroller was also available in a more convenient layout :xeye: . O and ofcourse I already ordered all the parts...
I will look for the gromets / eyelets, thanks for the responses up till now... I you have more suggestions for a beginner like me, please let me know. Because if I don't want to step in every pitfall there is... My pcbs are also decorated with perfect sharp mirrored text sections :D. |
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| jackinnj |
| to hold the bit. It uses compression to hold the bit in place. If it's not "True" the bit wobbles. |
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| vpharris |
| quote: | Originally posted by edm
The drills are 'Wolfram-Vanadium-Stahl'. Oh and the drills are not 8mm but 0.8mm. I just bought the drills so they should be sharp, I hope. |
I don't think that they are carbide bits; they're vanadium steel. Steel of any sort dulls very quickly drilling through the glass in the boards. You should make a good effort to get a carbide bit. It may solve all your problems. |
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| edm |
| quote: | | to hold the bit. It uses compression to hold the bit in place. |
Thanks for clearing that up, the drill doesn't seem to wobble..
Well then tomorrow when the shops open again, I have to buy myself some carbide bits. And next batch off pcbs I will first drill then etch... |
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| jackinnj |
| www.toolbitcity.com -- they have groups of drills which you would most probably use for PCB's . I assume they will ship to the Netherlands -- Global Priority Mail is only $4. |
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| haldor |
Hi Emiel,
One thing about carbide bits is they don't bend, they break. Make sure your PCB is clamped down and can't crawl up the drill bit or you will be going through several bits per board.
Anybody want to buy some very short carbide drill bits?
Phil |
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| jackinnj |
| my carbide bits break right off at the shank |
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| edm |
Today a friend of mine gave me some different bits and the difference is amazing. Before the copper always was 'pulled' up by the drilling and after some holes the inner side of the holes looked dark. With the new drills I get perfect sharp round holes and the pads stay in place. So I had the wrong drills :( .
So again I learned something, thanks for all the replies!!!
Emiel |
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| stadams |
I used to use the same type of Dremel press for drilling PCB's until I started using a regular industrial drill press. It turns at 750 rpm with much greater torque allowing me to make much more clean and accurate holes.
I have also waffled back and forth concerning the carbide vs. steel drill question. I have come to the conclusion that for the amount of drilling that I do, the high-speed steel drills work fine for me. I purchase them through Digikey for a couple of dollars each compared to at least seven dollars a piece for the carbide type. I am still using my first steel drill after about 200 holes and it has yet to show signs of wear. I have to agree that the carbide drills have zero ability to bend or flex and will shatter if there is any misalignment. One negative against the steel drill is the shank is the same size the hole diameter which could be difficult for some drill chucks. Both bits are made by Injectorall Electronics, which also produces all necessary PCB materials.
Later, |
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| MRehorst |
Drill first, then etch. Even with sharp tools, why temp fate?
I've built a lot of boards on a T-Tech mill and after my first couple I learned to drill then route. Now I wouldn't do it any other way.
MR |
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| jackinnj |
You can pick up 0.0135" bits pretty inexpensively from Digikey. If you have to drill a lot of holes on 0.100" centers you can use this bit to drill an acurate pilot since it won't cut the pad and the bit itself will be sucked into the precise center. this is the bit I use when making splice runs on the top side of single-sided board, but it's very handy in making a pilot hole for precise mounting of headers, DB sockets etc where the leads aren't flexible.
Of course, I hope to be using the milling machine just as soon as I get some stepper motors...the software has an adjustment to back out backlash so we should be good to ten-thousands of an inch. |
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| Philo |
| A good source for bits are the 50 piece sets list in the Grizzley catalog. They are broken industrial solid carbide bits with 1/8" shank that have been resharpened. They are a mixed bag and don't cover every size but cover the sizes we use pretty thoroughly. Most have anodized collars with the sizes engraved on them and come with a nice stand. The price is right at $12.95! http://www.grizzly.com/products/ite...5630442&DS_ID=1 |
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| tiroth |
| Drillbitcity.com, who also sells on eBay, has been a reliable source of resharpened bits for me. |
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| edm |
Just finished a double sided board with the following recipe:
1) expose/develop one side
2) drill with newly bought carbide bit, expensive but WORTH it
3) align mask using holes
4) expose/develop
5) etch
This will be the recipe for all my coming pcbs. This gives perfect results. The allignment between bottom and top using the holes makes live easy and precise. I was a little bit scared for 'under-etching at the places of the holes, but this did not happen all of the solder pads are intact. I am so happy :tongue:
The only note to myself is use gloves next time, I used NaOh this time to develop and this is slightly more aggresive then what I used previously. So I ended up with a perfect board and a blister on my index finger. A well you have got to make some sacrifices, right?
Thanks again for helping me out!!! |
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| jackinnj |
when working with NaOH -- even though I did chemistry (and physics) as an undergaduate I failed to remove my ring and also got a nasty burn when it came in contact with stainless steel -- nice electrolytic reaction.
You can use a different, higher pH base like sodium bicarbonate to develop the board -- less dilute, takes more time. In fact, I think that the sodium hydroxide is perhaps too active. |
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| jackinnj |
| The weborder came two days later. I purchased a 1/4" collet so I can use them on the mil. Here's what you get for your $15.65: |
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