Safest technique for removing SOIC chips on SE/30 like UD8, UE8, UF8, etc.

[djc6]

I am going to attempt replacing UG8 on my SE/30. What is the best way to remove SOIC chips like these?

I've done some research and Chip Quick (ChipQuick?) SMD removal solder is a possible way, though the "mess" afterwards is a little concerning - looks like you need to use this stuff sparingly! I have some already on hand I've just never used it.

Another video I saw someone scoring the legs with a utility knife that seemed to work well, but I don't want to damage the board. I do have kapton tape to protect the surrounding area. Link should start at 2:44

I've seen the same done using flush cutters.

Adrian from Adrian's digital basement swapped UF8 between two SE/30s for troubleshooting, and he used hot air station which I don't have. But I didn't quite understand how he soldered the new one back on - also using hot air? I didn't see any cleanup of the old solder or putting on fresh solder which I would want to do. Link should start at 20:14

I was going to use this technique to solder on the new chip - that seems straightforward, I'm still up in the air about least risky way to remove the old chip.

 

[JC8080]

Personally I did not attempt any SMD work more complicated than recapping until I bought a hot air station. I bought this one from Amazon for $40 and it has worked fine for me. It is well worth the investment. ChipQuik is expensive and can be a bit of a pain. It is good to have around as a standby for certain situations, but the hot air station is always my first choice.

Edit: spelling

 

[djc6]

Personally I did not attempt any SMD work more complicated than recapping until I bought a hot air station. I bought this one from Amazon for $40 and it has worked fine for me. It is well worth the investment. ChipQuik is expensive and can be a bit of a pain. It is good to have around as a standby for certain situations, but the hot air station is always my first choice.

Edit: spelling

$40 is pretty good deal. How do you protect the surrounding area? Aluminum foil? Mostly concerned about causing more harm that good with the hot air.

 

[superjer2000]

I don't love hot air as I have convinced myself it can't be good for the board or components to make the entire package so hot the component can be removed. So I use chipquik for this and frankly it's super quick and not hard to clean up. As you noted a bit of practice on how much to use goes a long way but I can remove those problematic chips on an se/30 in like 30 seconds with chipquik.

 

[ymk]

How do you protect the surrounding area? Aluminum foil?

Foil could work. I use aluminum tape.

If you have a fairly powerful iron with a miniwave or other broad tip, you can (with plenty of flux) drag a large blob of solder over the pins and lift the chip.

 

[croissantking]

I repeat buy some random low melt solder off eBay, it’s not as good as quik chip but it also doesn’t haven’t the massive price tag. For anything larger than a small SOIC I still use hot air with it but the heat is turned down much lower than would otherwise be necessary.

So for example if I’m desoldering a PLCC chip, I flood all the pins with the special solder. Then I use one hand to heat (with hot air) one side, or one corner of the chip gently (at around 200°C) and using my other hand I quickly go around it with the soldering iron melting the solder. The side that’s receiving the hot air stays melted for longer, so I don’t have to keep going back to that side with the iron. It takes only about a minute or two for it to free itself from the PCB.

The downside is cleanup and that I go through quite a lot of solder wick. The low melt stuff is quite easy to gather up and reuse so it lasts a while.

 

[JC8080]

Hmm you guys are having me rethink my reliance on hot air. I do admit I never feel great about putting extra heat into the board.

 

[obsolete]

Well I agree with you JC8080, I am on team hot air. With a small nozzle to focus the heat, and reasonable temperature and airflow settings, it's very easy to lift SOICs like these without any damage to the board or surrounding components. Use liquid or paste flux (I actually really like the ChipQuik stuff, SMD291) on the pins before heating and it will break up the oxide and allow the old solder to melt evenly. Very quick job once you get the hang of it, and minimal clean-up afterwards.

 

[zigzagjoe]

Hot air + Kapton tape for masking if required ie. heat sensitive components (plastic, capacitors) nearby. Quick and easy for SOIC. I've never fried a chip due to too much heat; unless you're really cooking the chip for minutes at a time I would not worry about it. Likewise for the PCB damage concern, any multi-layer PCB should be fine with hotair at a reasonable temperature.

To recondition pads with contaminated solder due to electrolyte leakage, I apply Chipquik CQ4LF and then wipe pads clean with solder-saturated wick. The extra solder in the wick helps dilute the contaminated solder and leaves a thin layer of fresh solder on the pad. In extreme cases it may be necessary to mechanically clean (ie. pick or scalpel) contaminants off the pad.

 

[jmacz]

I'm also in the hot air camp. I use aluminum tape to protect everything I'm not intending to heat.

 

[Callan]

Hot air... Single edge razor blades make quick/ great heat shields, btw. If I'm being super careful I'll use kapton tape, a sheet of copper, or aluminum tape (depending on what surrounds the part I'm trying to take off).

 

[nyef]

If you want to save the chip (for possible re-use), hot air, no question. But use a pre-heater. Having the board sitting on a pre-heater for a while to get to a higher baseline temperature is going to reduce thermal stress as you get the solder to melting temperature, the solder is going to be slower to harden again, and it's going to be faster to do the actual removal. This also makes for less stress on the pads, which is a definite concern if you're dealing with the aftereffects of bad caps.

Now, if you don't care about the chip? Chew through the pins with some side-cutters, use your iron to pick up a pin at time from the board, do a cleanup pass with the braid, then IPA it, after which you can lay down your replacement chip however you want.

 

[Juror22]

Hot air also (nice tip about the single edge razor blades btw, I'll have to try that). Like the OP, I have some ChipQuik (generic though) as well and haven't used it yet either.

 

[joshc]

If you want to get fancy, there are hot air nozzles shaped for certain chips so that only the legs are heated up rather than the whole chip. Or use kapton tape.

 

[Daniël]

I don't love hot air as I have convinced myself it can't be good for the board or components to make the entire package so hot the component can be removed.

While there are limits and nuances to it, components and PCBs are made to withstand some amount of heat exposure.
After all, the way SMD components are soldered to boards during manufacturing, is by going through a soldering oven, at temperatures that can melt the solder paste that was applied prior to the components being placed by the pick and place machine.

 

[JC8080]

If you want to save the chip (for possible re-use), hot air, no question. But use a pre-heater. Having the board sitting on a pre-heater for a while to get to a higher baseline temperature is going to reduce thermal stress as you get the solder to melting temperature, the solder is going to be slower to harden again, and it's going to be faster to do the actual removal. This also makes for less stress on the pads, which is a definite concern if you're dealing with the aftereffects of bad caps.

Unfortunately I don't have a pre-heater, largely due to space constraints in my work area. What I do if I am going to be removing a larger chip that will require quite a bit of heat moving from side to side around the chip is to preheat the surrounding area with hot air, either from my hot air station or a hairdryer on high. If it's a relatively small area I want to hear I will use my hot air station as hot as it will go, and I will move around the area in circles to spread out the heat, at a distance that is not putting too much heat into any components or the board. For larger areas I will use the hairdryer for a few minutes to heat the area. Of course this additional heat in the PCB does not last long, but I have convinced myself it is better than nothing.

 

[obsolete]

If you want to get fancy, there are hot air nozzles shaped for certain chips so that only the legs are heated up rather than the whole chip. Or use kapton tape.

I use these for PLCCs, love 'em.

 

[djc6]

Since I just want to replace one chip (UG8), and don't see an ongoing need for a hot air station, I'm going to try the chip quick method, or the method in original post where you score the chip legs with a blade and just essentially cut the chip off.

One of those no-name 858D cheap <$50 hot air stations might be in my future if I end up having to replace multiple chips.

I also came across the Quick 957DW+ as an entry-level hot air station, an upgrade from the 858D models since it doesn't use a small fan in the handle:

https://www.tequipment.net/Quick/957DW+/Desoldering-Equipment/Rework-Stations/?b=y&v=171729

And of course, Louis Rossmann sells the Atten ST-862D that he seems to use inside his shop, which is quite the endorsement:

Hot Air Stations

store.rossmanngroup.com

 

[dalek]

I wouldn't put a knife or sidecutters anywhere near a soic. To much chance of slipping and cutting traces.

Chip quick or hot air... I'd suggest buy a cheap hot air station as they are very useful for hobby electronics.

 

[djc6]

Okay, I was able to to remove UG8 easily using the ChipQuick SMD removal solder. The hard part was I struggled to find online what I should set my soldering iron to! The melting point of the solder is mentioned everywhere, but this is not the same as what you should set iron to for chip removal. None of the videos I found of people using ChipQuick mentioned the temperature their iron was set at. I finally found this document on DigiKey's website:

https://www.digikey.com/Site/Global/Layouts/DownloadPdf.ashx?pdfUrl=21CE38B971494AA89C2F3E7E35B85563

It says "use a solder iron set at 500 to 600Deg. F with a flat chisel tip" Once I did this the chip was removed in seconds.

I struggled to clean up the mess however. I used way too much because I had the temp set too low, so it was kind of a mess. USE PROTECTIVE EYEWEAR. I do this every time I solder anyways, and I actually had some minor "splashing" of the ChipQuick when cleaning it up because the solder wick I was using flicked it toward me. The instructions say to use a cotton swab dipped in flux - I used the flux ChipQuick included with the kit, but zero solder stuck to the swab.

Not perfect soldering, but I think pretty good considering my hands shake and UG7 is kinda in the way and my first time doing SMD.

Most importantly, I have video now on my SE/30 so happy I was able to narrow down which chip was the problem instead of throwing the parts cannon at it. I noticed UF8 and UG8 had/have no markings on them whatsoever, maybe they were substandard components.