Techniques to remove surface mounted components from boards

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Hi Freaks,

What are some commercial techniques to easily remove surface mounted components without damage? In my work, sometimes we get parts with different packages which are surface mounted on customer app boards and when we get them the packages are badly damaged (balls missing in case of BGA's, pins bent.etc.).I was wondering if the board guys are using the right technique.

Thanks.

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For BGA, so called rework stations, they are a bit expensive. For other smaller part, hot air solder equipment, operated by hand and often you need to replace IC by new one because they can be damaged.

There probably are some videos of bga rework at youtube.

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I use Chip Quik.

Leon

Leon Heller G1HSM

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Chip quick looks interesting. But what happens if you have multiple parts very close to each other on the board? Like a motherboard for example?

I thought they had an automated machine which you can put the board in, the board gets scanned for parts, and then you can specify which component to remove (by desoldering)

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I don't think there is any such machine.

Leon

Leon Heller G1HSM

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Yeah something like the Xray machines they have at the airports where they can point on the screen and determine what it is. Some form of image recognition being used to detect parts.

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Electronics manufacturers actually use X-ray for inspection of hidden layers as the top layer under the BGA. Other machines use CCD cameras to inspect the board and compare each component and soldering to entries in a database. Very expensive machines for volume production.

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I don't think that there are any rework machines that work like that, though. They are all used manually.

Leon

Leon Heller G1HSM

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Usually it's more important to leave the board undamaged, after all the component being replaced is already kaputt.

With ICs I usually cut all legs with a sharp knife, then I simply sweep up all pins with a big tipped soldering iron. A bit of desoldering wick, a bit of cleaning and it's as new.

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npat_avr wrote:
Hi Freaks,

What are some commercial techniques to easily remove surface mounted components without damage? In my work, sometimes we get parts with different packages which are surface mounted on customer app boards and when we get them the packages are badly damaged (balls missing in case of BGA's, pins bent.etc.).I was wondering if the board guys are using the right technique.

Thanks.

you seem to want to save the component. The question is why would you want to save a component you are removing from a board? presumably you're removing the component because it is not working.

Most components can be de-soldered safely, and well enough that they can be re-used, as long as care is taken during the removal. BGA's on the other hand are a different story. Once removed, they need to be re-balled if you wish to re-use the part. There are re-work machines to do this, but often it is not worth ht effort.

Writing code is like having sex.... make one little mistake, and you're supporting it for life.

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You are right,glitch. These are customer returns that are removed off of working boards and we normally test them to make sure they are fails which is why we want to save the component.
This is a package related question, but when you re-ball a BGA package, aren't you compromising the integrity of the package? Have you not changed the electrical characteristics of the package?

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Re-balling is often done with new RoHS parts if they are to be used on boards with lead solder, as well as parts that are to be re-used. How does it change things?

Leon

Leon Heller G1HSM

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I like to remove some chips that are working.

Once I bought a mutilated sound card because it had sound chips I was interested in. So naturally I wish to remove the sound chips and throw away the PCB.

This way I can for example make an AVR FM synth for example.

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Heatgun works nicely ;)

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If you want to have all SMT components at once, put the whole board in the SMT oven and reheat it.

Stealing Proteus doesn't make you an engineer.

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What happens with components that are also glued?

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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You can use a hand held hot air rework station (a heat gun used in DIY is NOT recommended!), look for brands like Aouye etc.

You can also use infra-red welding stations, these have come down to a semi reasonable price, depending on what you are doing (hobby or small business use).

@ js - glued chips can be removed with hot air. A scalpel and solder mop can be used to clean up the board. Just need to be very careful.

After working in mobile phone repair for a few years, its amazing the kind of tricks you can pick up!

Btw, youtube has some pretty cool videos, search "pcb rework" or "bga".

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Depending on the MSL of the device being removed, you may need to pre-bake the device/PCB if you plan on using it again.

Also, PCBs and components have a limited amount of heat cycles before permanent damage occurs.

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Aren't parts subjected to more heat and temperature "stress" when you are soldering them in than when you are removing them from the boards? Because when you solder them in, you have to go slightly higher than the reflow temperature for the solder to flow in the holes and make good contact (prevent dry solder joints)?

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For non-BGA parts i apply a bismuth soldering alloy which melts at 140 degrees Celsius on all pins, extract the part with hot air set at 150-160 degrees, clean both pcb pads and pins (if i reuse that part) with desoldering braid and flux.

Dor

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npat_avr;

From a BGA/PCB prospective:

It's the cumulative effect of all heat cycles that will damage the part and PCB. Every heat cycle after initial placement drastically erodes the MTBF of the part. From a QA perspective I would be quite hesitant sending out a product that had the same BGA replaced several times.

If you have lots of cash look at the Summit series of rework stations. We have the 750.

http://www.vjelectronix.com/Rework%20systems_Summit_750.html

Oc.

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Isn't it so that in some markets replacement is not allowed at all, like medical? When a freshly produced board does not work, the whole board is discarded instead of replacing maybe a single faulty component. I can remember someone telling me that once.

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ocnek wrote:
npat_avr;

From a BGA/PCB prospective:

It's the cumulative effect of all heat cycles that will damage the part and PCB. Every heat cycle after initial placement drastically erodes the MTBF of the part. From a QA perspective I would be quite hesitant sending out a product that had the same BGA replaced several times.

If you have lots of cash look at the Summit series of rework stations. We have the 750.

http://www.vjelectronix.com/Rework%20systems_Summit_750.html

Oc.

Hey. I have a maschine like that. It have been resting for a fifteen tears. Ready to give away, or excganged by some funny thing, to pay for cargo.

It resides in Norway.

HM

HM

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npat_avr wrote:
Aren't parts subjected to more heat and temperature "stress" when you are soldering them in than when you are removing them from the boards? Because when you solder them in, you have to go slightly higher than the reflow temperature for the solder to flow in the holes and make good contact (prevent dry solder joints)?

In an production reflow process, the board is pre heated, soaked and then ramped up to the higher relfow temperature where it dwells for only a short time. The board is then allowed to cool off at a uniform rate. This prevents solder cracking and the PCB warping.

In a removal situation, typically with an unregulated and uncalibrated hand held rework station, there are none of these measured to prevent damage.

It is possible (maybe necessary in some cases) to use a pre heater for your BGA rework, these are small heaters which sit beneath the PCB for a few seconds before begining work with the hand held device. This just creates a uniform heating of the PCB and components to prevent damage (also held Pb free solder to melt!).

You can check the device data sheet, usually they contain info on the reflow profile used and the amount of permitted reflow cycles.

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I've done it by accident a couple times.

If you don't know my whole story, keep your mouth shut.

If you know my whole story, you're an accomplice. Keep your mouth shut. 

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If you have complete disregard for anybody's lungs withing a 50 mile radius (like me) i find that a propane torch (or MAPP gas in my case) held IN PARALLEL with the underside works good. this is obviously a brute-force and should only be used if you have complete hate and disregard for the PCB that you are stripping.

also, some guys at another forum suggested a standard $30 hot plate that you can get at wal-mart.