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SMD repair

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DirtyLude

Well-Known Member
Use a hot air gun/station.

If you are doing just a few here and there, I've gotten away with using torch/jet style lighters like:
**broken link removed**

Use a long tweezers to hold it and apply pressure upwards while you heat it and detach it from the board.
 
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3v0

Coop Build Coordinator
Forum Supporter
In addition to what DirtyLude said.

The problem is getting heat to the pins and pads where it is needed without overheating the chip or board. Gel flux brushed on the pins or even enough solder to bridge pins can help.

SMD pads are easy to lift. Go easy on the pressure. I have a ditty called a chip popper. Is is just a small dowel with a wire fork you place between the chip and the board (not always possible). The weight of the dowel lifts the chip when it is ready.
 

Bengt

New Member
Short circuit all the pins with a short wire and add tin. Lift one side at a time or lift the first up a little and go to the other side and back to the first side again. The quick and dirty is to just use a lot of tin.
 

sansgp

New Member
I would use a solder wick to remove the solder from the SMD terminals (some flux would get into the pads from wick) and then heat the terminals together with a solder iron while holding a tweezer in another hand, gently twist / shake the IC chip left / right and you will begin to see a slight movement with the IC after a short while. Upon seeing the movement, gently slide the IC to one side and it will come off easily. Due to the presence of flux, the pads will remain wet and intact. No damage what so ever. here, Key is: you need patience! and need to practice, to enhance the skill level. It is easy, can be done. Try ... Good luck.
 

jpanhalt

Well-Known Member
Most Helpful Member
There is also something called ChipQuick (Chip Quik: Easy removal of surface mounted devices). The company now makes a lead-free version too. It is simply a very low-temperature solder. Think of Woods metal, but not that alloy. To use it, you melt some onto each pad to form a low temperature alloy with the solder. You can remove the chip using a hair dryer. Then use solder wick to clean up.

John
 

tunedwolf

Well-Known Member
If you want to be certain that you do no harm when lifting and placing SMT devices, use good quality liquid flux on the joints/ board before you start. Pre heat the board to 100-150 degrees for a minute or so, and then tickle the pins, or in the case of BGA, the entire part, with either IR or a Hot Air wand until you reach fluid point, which will be the melting point of your solder. Remember lead free solders have a higher temperature melting point. Then simply lift the device away and allow the board to cool. In any case do not go over the rated permissible temperature of the device or you risk damaging it, or worse, scorching the board or delaminating the pads and track. Clean up using a low powered solder pump/ sucker with a silicone nozzle. Do not use one with a hard nylon nozzle or you will pop pads left right and centre with the recoil. If you're good with it you could use solder wick, but a word of caution, on fine pitch pads, never ever remove the heat without removing the wick at the same time from the joint or you will tear the pads clean off the board. Also when using Hot Air, if there are other smaller parts in close proximity to the device you are removing/ replacing, use some strips of Kapton tape around the device to stop you blowing them right off the board. Nothing worse than making a great job of a QFP Flat Pack rework then realising there's no resistors around it anymore! SMT glues have a breakdown/ melting point of around 150 degrees, so no problem there either as you will be well above that when the joints are fluid.
Always fully clean any old flux off the board before applying new flux prior to device placement.

The best advice I can give you is take your time, don't rush things. Work in good light, a magnifier also helps you see what's happening, and use the right tools for the job. Apply only enough heat to get the job done with ease. Don't be tempted to turn the temperature up beyond the max that the device can handle, particularly in the case of expensive or sensitive chips, just be inventive in the way that you get the device to temperature in the shortest period of time.
Pre heating the board will greatly help you quickly get the solder fluid without damaging the board or device. Never lever at a device, try to twist it off, or apply any kind of upward pull on it until the joints are fully fluid or you risk tearing up pads and track. When cleaning up the board be careful with wick on fine pitch pads, and never use hard nylon nozzles on solder suckers.

rgds
 

tunedwolf

Well-Known Member
About the board preheat. As of yet I have not used it.

How about wrapping the PCB in aluminum foil to prevent hot spots and using a preheated kitchen oven to preheat the PCB prior to repair ?

I dare say you would get away with it if the oven were pretty stable temperature wise and you immediately performed the required process after removing the board from the oven. The biggest problems I see might be keeping the temp stable inside the foil and within limits for the components on the board and rapid cooling when you remove it from the oven. The idea is to maintain an even stable temperature during the soldering process so that neither the board or components are stressed and that the board can relax and be as flat as possible. The last point being very important for any kind of BGA rework.

rgds
 
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