cutting traces, lifting up IC pins, what tool to use?

[danny davis]

What tools are the best to cut PCB traces?

What tool is the best to LIFT up fine pitch pins, they don't break?

What tool is the best to lift up SMT IC pins? so they don't break?

What can I put under an IC pin after I have lifted the pin up so it doesn't short out to the pad

Because when I lift up the IC pin I put a wire on it to re-route the signal so I don't want it to touch the PAD underneath anymore, but I don't know what to put on the pad to not make the pin short out to the pad on the PCB when the IC pin is Lifted? what can i use please?

Do you use a soldering iron to lift up the IC pin? But the IC pin mostly breaks off

 

[weird_dave]

I use a pointy scalpel blade for cutting tracks and leg-lifting of SMD pins. After lifting, I use small pliers (where possible!) to straighten the leg flat horizontal out from the chip, this makes it easy to attach wires.
I generally don't bother putting anything on the pad under the leg, it should be lifted far enough that it can't touch the pad. I clean the pad of excess solder using solder wick.
For SOIC style devices, there's usually enough space to connect a wire onto the pad and still not have problems with the pin above it touching

 

[danny davis]

Ya if i lift the pin up to get it to not touch the pad , because i soldered a wire on the pin you have to lift the pin higher and it breaks the IC pin

What would u put on the pad to not touch the lifted IC PIN?

 

[KJ6EAD]

I like a small ball engraver tip on a Dremel for trace cuts. The 190 and 191 bits are about the right sizes. I can't understand the rest of your questions.

Now I see what you're up to after reading Weird Dave's response. Any thin insulator material such as a bit of Kapton (polyimide) or polyester tape folded over to keep the adhesive out of the way. Maybe just leave a little adhesive flag on the end to hold the insulator down on the PCB. The Kapton tape has the advantage of being able to withstand soldering temperatures.

 

[danny davis]

I LIFT the PIN up off of the IC chip, I don't want it to touch the pad underneath it anymore

What can I put so it doesn't touch the pad anymore to prevent it to short out?

 

[KJ6EAD]

Look at my last post. I was editing while you were composing your post.

 

[danny davis]

there is not enough room to use kapton tape

Do you have anything else in mind?

Also When the Pads Lift off the PCB board from leaving the soldering iron on it to long

What can I use to Repair the pad? do you use 30 gauge wire?

 

[KJ6EAD]

There is not enough room to use kapton tape. Do you have anything else in mind?

No.

When the pads lift off the PCB from leaving the soldering iron on it to long, what can I use to repair the pad?

Don't do that. I think repair techniques were covered in your other thread.

Do you use 30 gauge wire?

Occasionally as a jumper for burned out traces.

 

[danny davis]

How do u fix a pad that has been lifted off of the PCB?

What do u do and use please?

I can't solder the component on the PCB , SMT

 

[CocaCola]

How do u fix a pad that has been lifted off of the PCB?

A jumper to to a common connection...

If this is new product and you are doing botched repairs, IMO the board should be scrapped not sold to a customer...

 

[(*steve*)]

Also When the Pads Lift off the PCB board from leaving the soldering iron on it to long

What can I use to Repair the pad? do you use 30 gauge wire?

For fixing errors (including your own as in the case above) you can use wire wrap wire. It is easy to solder to, and fine enough to connect to fine traces.

 

[CocaCola]

For fixing errors (including your own as in the case above) you can use wire wrap wire. It is easy to solder to, and fine enough to connect to fine traces.

I generally just use the clippings off of through hole resistors and caps, I keep a little container full of them just for this purpose... That or I always have a few rolls of fine gauge Kynar insulated wire wrap laying around...

 

[danny davis]

Ya but if u use wire wrap or bare leads off of resistors , the SMT component doesn't sit FLAT on the PCB, it is raise up on one side

I need it FLAT

 

[(*steve*)]

Ya but if u use wire wrap or bare leads off of resistors , the SMT component doesn't sit FLAT on the PCB, it is raise up on one side

I need it FLAT

You solder the wire to the TOP of the component lead

 

[danny davis]

Some SMT components you can do that but not all

 

[(*steve*)]

In that case you learn better soldering technique.

If it wasn't caused by your own incompetence, it may be a reason to discard that unit.

I presume you're talking BGA devices or other devices with contact under the device. I've not had need to fix much stuff like this, but I did repair a USB drive that someone had "bent", breaking a solder connection to a chip that had only the smallest visible connection on the edge of the package. In that case it was simply a bit of solder that was applied. Maybe I would have been more heroic if that hadn't worked and the data was *really* valuable...

But I think we've been here before. You shouldn't be lifting tracks with your soldering iron. I remember doing that when I was about 12, but I quickly learned I was using the wrong technique and I fixed the problem.

I do have a "silver" pen that I can use to draw conductive traces. I guess I could use that to repair a trace. However, you have to be really careful soldering to it (which you can apparently do) and it sounds like it would not be an option for you.

edit: this

 

[CocaCola]

I need it FLAT

What you need to do is to learn how to solder properly so that you are not damaging it in the first place...

Have you run by using jumpers and repairs like this past your employer? Are they OK with the final 'new' product going out the door looking like a returned and serviced component?

When I worked for Motorola in some cases a few expensive components where stripped off destroyed boards (a few whole units generally tossed in a box for component stripping in repair areas) the rest were were sent to the back corner of the factory where they had a drill press setup... The boards were met with a few plunges of that drill bit through them and then they were tossed in the trash, so that no subpar units ever never made it to the market as new...

 

[KrisBlueNZ]

If you're having problems with pads lifting off the board, here are a few suggestions from my limited rework experience.
Use a smaller bit, a lower iron temperature, a temperature-controlled iron, solder wick instead of a solder sucker (these can jump around and bump the pad), or ideally a hollow tip iron with suction pump (i.e. a desoldering station).
Use fine wire (e.g. wire-wrap wire) and minimal solder for rework. Clamp the board firmly so it is really stable, and rest your hands on it (like how a dentist uses your jaw to stabilise his hands).
Use an eye magnifier or a magnifier on an angle-poise arrangement, and at least two bright lights.

 

[KJ6EAD]

The problem is not too much heat but heat for too long a time. It may be counterintuitive but you need more heat so you can spend less time on the joint. You want to quickly heat the pads/lands and component leads but not soak heat down into the epoxy.

 

[KrisBlueNZ]

The problem is not too much heat but heat for too long a time. It may be counterintuitive but you need more heat so you can spend less time on the joint. You want to quickly heat the pads/lands and component leads but not soak heat down into the epoxy.

I see. So I guess to minimise the heating time, you need a quick way to remove all the solder, like a hollow tip iron with a strong suction pump. Once the solder is gone, you should be able to detach and lift the leg using a small blade like a scalpel.
I googled "SMT removal" and most of the results were for a product called Chip Quik which you add to the existing solder (you melt it in, using an iron) and it lowers the melting point of the solder so it stays liquid for a much longer time. Then you just heat up all the leads and slide the device off the board!
There's also an article at http://www.engadget.com/2006/03/07/how-to-make-a-surface-mount-soldering-iron that shows you how to modify a cheap Radio Shack desoldering iron for continuous hot air output using a fish tank pump.
I guess the reason why leads break off at the edge of the device would be that they're bent too far, or too many times. Once the foot is off the pad, you would need some way to straighten out the two kinks in the leg without moving the bend at the edge of the device.
Maybe it would be possible to make a jig that clamps the uppermost part of the leg (the "thigh", you could call it) so you can straighten the knee and ankle independently without moving the "hip" joint?
If this jig could be used while the foot is being desoldered from the pad, there would never be any movement at the edge of the device.
Just some random thoughts.