Drilling a PCB

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hi All,

I have a quick question. When working with populated PCBs and wires tear out or other components don't desolder too well, is there any reason not to drill out the remaining junk?

I have tried using solder wick (braid with flux) and a desoldering pump but it doesn't get some of the remnants out.

I have, by trying to hard with heating again and again, removed some soldering pads. These were just anchors on the bottom side only holding in the component and not connecting to anything else. Maybe you have ideas how to remedy that too?

If drilling is ok, what size bit do I use to match what most manufacturers use for hole size in their production PCBs?

Thanks. Your experience is greatly appreciated!

Regards//Keith
 
I think you will struggle to drill out rubbish as the hole size will be something like 0.7-0.8mm and if the bit encounters anything that pushes it off course it's likely to break. I've never had a problem removing stuff, a technique I use is to tap the board on the bench in an effort to bang stuff out. Then clean up with braid. I find solder suckers quite rubbish.

If you can't get the angle of the board right to tap (due to components etc), hold it firmly and whack your hand on the bench.
 
Hi,
If these are plated through then drilling is likely to remove most of the plated through tube. It's that tube that gives a major increase in strength to the pad to substrate adherence.

Drills sizes are likely to be 0.6, 0.8 and 1.0mm. They may add on a bit for the plated through thickness to bring the usable diameter down to the wire sizes.
If you're in the US then all bets are off for equivalence in drill sizes.
 
Hey Mates,

Thanks for the replies. We do import quite a bit from the rest of the world including the UK (like Jaguars, MGs and my favorite, the "Sunbeam Tiger"). We have metric bits here and they are becoming quite universal so I will purchase all three sizes.

When the PCBs are made, how do they line the barrel, with tinning or copper? Is it worth trying to replace the solder pad anchor?
 
If you lose a pad, just bend the component lead to lay onto the track then solder it down. You will need to scrape of the resist if it's there. Pads come off because of too much messing with them and too much heat for too long. Clip leads away (to minimise heat input needed) and use the techniques I mentioned and you should have good success rates.

I'm not sure you understand how small 0.6mm is and trying to work at that level with hand or even manual bench tools!
 
As I look through a piece of stripboard, I have an idea how small it is. I know what you mean about the bit wwandering off even with a drill press just because the bit is so small it remains flexible. It will, in many cases, go around rather than through. So the only way is with a very fresh bit, very slowly with a drill press with the board perpendicular to the bit and don't allow any movement.

Sounds like a last resort.

I am very interested in increasing my success rate, otherwise this would not be a hobby. It would be more like Purgatory!

I can use the bits for modifying PCBs and prototype and stripboards too. Thanks!

Andrew, I need a microscope on my head now like a Neurosurgeon!
 
Please try to take this without offense, but there's something very wrong with your technique or your tools. Drilling is almost never the answer. If you don't have a fancy de-soldering station, and who does, you need an iron with good thermal capacity, but not excessive temperature. That generally rules out small tips. Nothing more than a 25W iron (or TC iron), and a flat or chisel tip of about 3/32". You need to apply solder and/or flux in order to quickly wet and remove the component, then finish up with braid or suction. I rarely use braid and don't really like the stuff- it's expensive and I tend to burn myself. Sometimes, however, it's the best choice. OTOH, all the common suction tools are absolutely useless except one. You have to have the large size "Soldapullt", model DS-017. The newer antistatic one, DP-200, is also ok, but doesn't seem quite as effective as the original. I have a drawer full of the small aluminum body types, and they're worthless. A small tipped iron that's too hot, plus one of those, is a recipe for board damage. Never try to remove an IC intact. Cut the leads, remove the body, then carefully remove each lead individually. Some very high end test equipment manufacturers have suggested not even removing components from their boards, but cutting out the body and soldering the new part to the old leads. My guess is they were thinking mostly of axial capacitors and larger resistors.
 
Hi Conrad,

No offense taken here. Thanks! The truth is always the best policy! I have a Hakko soldering station with a medium Soldering Iron and chisel tip. You are right about too much heat. as I went back and it stopped progressing I turned up the heat (I know, this is painful for you guys to witness). It was stranded wire that broke off and nothing was protruding from either side of the board. The solder was different on these two connections too, it was real hard and wouldn't melt! So now I have learned. Also the other place I had some trouble was removing the OPA627, I was trying to save it for re-use (somewhat expensive and damned near impossible to find anymore).

I think it is time to go garbage picking and practice on someone else's garbage instead of my own Electronics! Anyone throwing anything out?
 
Sometimes things just don't work out, but on that wire I would have applied more solder- you have to keep things liquid and dross free. Then, with just enough heat to keep it liquid, tried to push the stuff out with a resistor lead or some other small piece of wire. If things weren't too tightly jammed in there, the big Soldapullt would just suck out the debris. I feel your pain on the OPA627. There are big square tips that will heat all 8 leads at once, but who has one of those when needed? I'd usually add a bit more solder to each leg, then use the sucker. If everything is working well, each leg will have almost no attachment. Then, you grab each leg at the tip with small pliers and see if it will wiggle back and forth. If not, apply just a touch of heat until it does. When you have 8 free leads, see if the body will move and come free.
 
I have occasionally resorted to a drill bit to clear a hole. But this was on a multilayer board where the hole in question was connected to an internal ground or power plane. I'd use a very small high-speed steel bit, like around #74, and turn it by hand using an Xacto handle as a pin vise. A carbide bit would be too brittle to get away with this.
 
I have a piece of 0.5mm stainless steel wire with a rounded end I used for clearing thru-plated holes. I heat the board and the wire at the same time, the wire slides through and you wiggle it gently as the solder cools. it breaks the surface tension across the hole making the solder much easier to wick out. The solder doesn't stick to the stainless wire.
Oxy-acet tip cleaning files should also work.

You don't burn your finders with wick if you leave 2 inches of soaked wick on. Hold the stiff, soldered, used end instead of the spool, the solder stiffens it up enough to poke it into where it's needed. Just let the spool dangle witrh another 2 inches of unused braid to stop the plastic melting.

Weller does do DIL blocks. These are great if you need to keep an IC. tin everything, ensure the leads are straight, stick the block on and bang the whole lot on the table.
You can make your own by tapping a thread on the end of a big ugly tip and using a block of copper busbar to make the tip.
the tip retainer sleeve will have to remain on the assembly if it gets stuck together.
 
I'm with Conrad,I would have added more solder.

I've noticed sometimes that even though it appears that the iron tip is making good contact,it isn't. The joint/solder never melts (or finally melts,after you've charred a hole through the board.)
Adding some solder seems to help make a better thermal contact. (kinda like silicone heatsink goop,in principal.)
Once you have a larger mass of melted solder,you should be able to 'tap' it all out pretty easily,in one bigger blob.
Sometimes I even heat up the joint,quickly pull the iron away,take a deep breath and blow a stream of air at the offending hole,as hard as you can (well,okay,but a nice brisk blow) to clear it out...
Oh,and mind where the solder is going to go! blowing hot solder down onto your leg/arm/etc. hurts!


Yes,Near my bench you will hear:
"Why you little...*Inhale..PUFFF!*...there we go!"
Or
"Melt,Da**it!!!"

:clown:
 
Gentlemen,

Thank you for all the responses. You guys are right, I added more solder evenyually. After the damage was started!

You know when I decided to use the OPA627 I was a purist about soldering in the op amp for best results. Now I have decided to become a realist! I just have to use top quality gold sockets!

You guys posted a lot of great ideas (which I will now employ) and can see you are able to relate to these situations (by experience).

DJ, I was saying a lot worse than "Melt Da**it!!!"

Thanks again guys!

Regards//Keith
 
Gold contacts will tarnish over time.

Compressed air is the easiest and the quick way to clean a PTH, but u have to take care of the flying solder. May be u can hold two tubes on both the sides and blow. just an idea. Device your own. Practice will make it easy.

Gajanan Phadte

edit: Caution-use safety glasses
 
Hi Gajanan,

Good idea, in fact I have a can of "Duster II" right here for blowing off/out dust from PCBs and Motherboards.

I will use glasses. Flying Solder is better than a flying PCB (like when I throw it across the room out of frustration).

Now, what about the sockets. Is there something better than Gold, both in the short term and over the long run (doesn't tarnish)? I haven't ever seen Rhodium Sockets (I like Rhodium for RCAs and Binding Posts because of great conductivity and minimal tarnishing).

Also, it seems the Machined Sockets are the way to go!

Thanks!

Regards//Keith
 
I have to admit, I had to resort to drilling in the same situation, a few nights ago with a doublesided board... tried everything, just could not clear all the holes... got it to as little solder as posible... till it formed a small dimple to guide the drillbit... drilled one track loose, before learning it had to be done slowly... especialy when you get to the track on the other side... untill it is drilled, you can just push it off.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.