VOGONS


First post, by techweenie

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I have a MB-8433UUD motherboard with the soldered RTC, and decided to buy the Aoyue Int968A+ rework station to assist with working on it. The last page of the instructions lists all the nozzles available for the hot air gun, and one in particular grabbed my eye - the SOP 1259. I checked the dimensions, and it's a PERFECT fit for the RTC chip. The only downside is that nozzle alone is $20, and very few places sell it. Mine arrived in the mail yesterday and I got around to using it today. IT WORKED PERFECTLY! In a matter of seconds the RTC dropped right out with no damage to anything. I've never seen anyone mention this method, yet it's so simple and brilliant. I did remove as much solder as I could the old fashioned way (which was also easy with the Int968A), but that wasn't anywhere near enough to get it out. The rework nozzles seem to be fairly universal, and there are some shady looking generic ones from China you can get. As long as you have a hot air gun you should be able to use it. I set the temp to 350C and airflow about 4.5. My particular motherboard had a rusted PS/2 mouse port, and the hot air made quick work of that as well.

Here is the exact nozzle I purchased: https://www.ebay.com/itm/Rework-Nozzle-1259-1 … 54AAOSwyTdauxHb

Reply 1 of 9, by feipoa

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I haven't heard of anyone using such a nozzle, but good to know it worked well for you. I still do not own a hot air solder gun. A few people have recommended a contact-based rework soldering gun which has the built-in automatic suction. Alas, I still use a traditional solder gun with the manual, spring-based, solder sucker.

Plan your life wisely, you'll be dead before you know it.

Reply 3 of 9, by MMaximus

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Just wanted to thank the OP for this information. I've recently bought an Int968A+ with the aforementioned nozzle, it's not cheap but as I have several boards and systems with soldered DALLAS chips, I thought the investment would be worhwhile.

I have no previous experience in soldering but I just managed to remove two DS1287 chips from two different motherboards with it today. Granted, I had to pull the chips quite hard with some pliers and they got a few bent pins, but I don't care so much as I'll put new chips and I don't intend to rework the old ones. The motherboard doesn't appear to have sustained any damage in the process and that's what I was most worried about.

Now I need to figure out the best way to remove the old solder - I tried with a cheap solder pump but it's tedious and doesn't work so well. I've also tried with braid but it doesn't work at all.

Here's a video that shows a similar nozzle being used to desolder RTC modules.

Hard Disk Sounds

Reply 4 of 9, by wiretap

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MMaximus wrote:

Now I need to figure out the best way to remove the old solder - I tried with a cheap solder pump but it's tedious and doesn't work so well. I've also tried with braid but it doesn't work at all.

For manual inexpensive solder suckers, I've found this one works the best. I recently cleaned out a RTC socket with it and it gets all the solder on the first hit. Well worth it.
https://www.amazon.com/Engineer-SS-02-Solder- … /dp/B002MJMXD4/

My Github
Circuit Board Repair Manuals

Reply 5 of 9, by _UV_

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wiretap wrote:
MMaximus wrote:

Now I need to figure out the best way to remove the old solder - I tried with a cheap solder pump but it's tedious and doesn't work so well. I've also tried with braid but it doesn't work at all.

Cheap braid doesn't contain flux, so it doesn't work at all.
Best cheap way to remove excessive solder (after using braid) - syringe needles for desoldering, just use big enough tip like K or D.

You don't need overkill hardware, just overkill knowledge of how and why this work. PACE YT channel have good tutorial on how to solder and rework soldering. It's old, but not very much changed since 1970-80 in the basics.

So, general advices are:
- use right tip (shape and size)
- use flux (good one, don't be scammed by referral Aliexpress youtubers)
- if contact have not enough solder feed a bit to make a better contact with your tip, it would 5-10 faster desoldering and not just heating up whole board (use good solder, same as flux - don't be scammed)
- don't use excessive temperature (230-260 for direct soldering and 270-300 for hot air for double sided or multi layer boards before ROHS Pb free, or a 20-30 C lower for one sided PCBs; also, if you set temperature too high active components of flux evaporate before doing it's work on oxidized surfaces and you may seriously damage PCB)

Reply 6 of 9, by dicky96

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MMaximus wrote:

I have no previous experience in soldering but I just managed to remove two DS1287 chips from two different motherboards with it today. Granted, I had to pull the chips quite hard with some pliers and they got a few bent pins, but I don't care so much as I'll put new chips and I don't intend to rework the old ones. The motherboard doesn't appear to have sustained any damage in the process and that's what I was most worried about.

Yes you can desolder through hole components with hot air stations and with some experience they work very well. But using pliers to pull out the chips with force - Really really don't do this! If the chip does not come out of the board with just an a minimum amount of force (in fact it should practically fall out) then you have not got all the solder molten on every pin. Have a look at the chips you desoldered. Do any seem to have small flanges or metal collars on or in the solder that is still on them? If so those are the vias that run through the PCB from the external pcb tracks . They connect to internal tracks as thePCB will have several layers. If you pulled any out then the PCB is pretty much scrap now. If you were lucky not to cause any damage this time, you probably won't be next time!

I assume you are removing the DS1287 chips because they are faulty? Then why do you need them in one piece? The way to do this sort of work is to use component snips like these https://www.amazon.co.uk/Component-Cutters-of … r/dp/B001YHJHEI to cut all the legs off the chip as near to the body as you can. Then remove the pins from the PCB one at a time. Simples.

Also apply 60/40 solder to all the pins before you desolder with hot air or an iron. It forms an alloy with the existing lead free solder and lowers the melting
point. This also means you can melt the resulting amalgamated 60/40+lead free solder alloy without accidentally desoldering nearby components

Now I need to figure out the best way to remove the old solder - I tried with a cheap solder pump but it's tedious and doesn't work so well. I've also tried with braid but it doesn't work at all.

To remove the reamaining solder, again add some 60/40 solder to each pad then use soldering iron and braid and dip the braid in flux first, I guarantee that will clean solder from holes 90% of the time. I use this type https://www.tme.eu/en/details/pasta-l-35/flux … a-do-lutowania/ you can get it on ebay. It is solid so you melt a channel in the flux with your soldering iron tip then dip the flux in the channel of molten flux.

If you still have problems cleaning out the holes, use the hot ait gun to pre-heat the area you are reworking to about 150C and then use the soldering iron braid and flux. Add more 60/40 and try again if you can't get the hole clear all the way through

Worse case scenario - use your hot air gun to heat the pcb hole from the rear side while pushing a stainless steel needle through also from the rear. No force required, just wait till the pcb is hot enough. If you add a it of 60/40 to th pad, then use the hot air you will see the shape of the solder go from convex to concave when the solder melts. Then push the needle in. https://uk.banggood.com/10-Kinds-Stainless-St … ur_warehouse=CN

Re hot air stations, the cheap 858D are perfectly good enough for this sort of work, I use one myself sometimes. If you want something much more capable than the 858D+ get the Quick 861DW. Thats is defacto the best you can get even compared to very expensive professional stations

Rich

Reply 7 of 9, by wiretap

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dicky96 wrote:

I assume you are removing the DS1287 chips because they are faulty? Then why do you need them in one piece? The way to do this sort of work is to use component snips like these https://www.amazon.co.uk/Component-Cutters-of … r/dp/B001YHJHEI to cut all the legs off the chip as near to the body as you can. Then remove the pins from the PCB one at a time. Simples.

That's more work than just desoldering all in one action to begin with. Plus, how are you going to get to the legs of the package when it is flush mounted on the board?

My Github
Circuit Board Repair Manuals

Reply 9 of 9, by dicky96

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wiretap wrote:

That's more work than just desoldering all in one action to begin with. Plus, how are you going to get to the legs of the package when it is flush mounted on the board?

Oh yeah I see what you mean. The method I posted works well for normal DIL ICs