How to unsolder/remove OCXO from PCB ? - Page 1
Forum section: electronics / general

author: nealix
author_rank: Regular Contributor
timestamp: February 25, 2022, 03:29:45 am
content: I purchased a couple of Vectron 10MHz OCXO's from China/eBay, and of course theyarrive attached to partial PCB's that have been cut (more like shredded) in a square around the OCXO.Has anyone previously had success with a method for unsoldering the OCXO fromthe PCB material without harming the OCXO? OCXO's typically have 5 pins, fairly stiff.I imagine, if I tried to use hot-air from the back of the PCB, that I would need sometype of shim or wedge on the top side to pry the OCXO off the PCB once it is hot enoughon the other side to melt the five solder pads?Ideas are welcome, but hearing from someone who has actually done it would be great.Thanks,Neal

author: Cerebus
author_rank: Super Contributor
timestamp: February 25, 2022, 04:32:20 am
content: I had a bunch just like that.What worked for me was to just go around the board and desolder all the pins in the usual way - whatever works for you, I use chemwik desolder braid. Then go back to each pin individually, stick a flat bladed screwdriver between the can and the board, heat that pin again until it just melts, take the iron off and slowly twist/level up the screwdriver just a little as the solder is freezing - the idea is to still have the board moving over the pin as the solder freezes. Go around the whole thing pin by pin. At the end you should have all the pins free and can just work around all the pins with the screwdriver levering each pin out a little, going on to the next pin, doing the same and just working around until the board comes off. If any individual pin doesn't want to move, just repeat the heat and lever while freezing bit again.I got a 100% successful recovery rate on the 4 I did. All working, all within manufacturer's specifications. Just required a little patience. Take your time, don't force anything.

author: martinr33
author_rank: Frequent Contributor
timestamp: February 25, 2022, 05:52:46 am
content: Other methods.1) Solder sucker. It often helps to add a little flux and solder first. Make sure that the whole mass of solder is hot. Then you might want to use the trick above and use the iron to do final separation of the pin.2) Low temperature solder removal alloy. Load up each pin with a little alloy and flux, and the oscillator will fall right out.3) Hot air and a little more solder. A hot air pencil can get the whole PCB hot enough that the oscillator will drop out.

author: bob91343
author_rank: Super Contributor
timestamp: February 25, 2022, 05:56:58 am
content: I successfully removed two of those. First use a solder sucker to remove as much solder as possible from each pin. Solder wick works too.Pry between the can and the board while heating one pin until the board bends a bit away from the can.Repeat for the other pins.Go around once again. If you are gentle, you won't cause damage.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: February 25, 2022, 08:41:40 am
content: 1. Needles from a syringe of a suitable diameter. Or purchasedhttps://aliexpress.ru/item/32858325617.htmlYou must heat the contact and put a needle on it. Solder does not wet stainless steel. You can easily remove the needle after the solder has cured.2. Mechanically cut the board into pieces. One conclusion - one piece. And then remove each piece separately.

author: geggi1
author_rank: Frequent Contributor
timestamp: February 25, 2022, 10:57:55 am
content: Use a heat-gun on the back of the PCB.You will be able to heat all four pads at the same time.To concentrate the heat you might have to put a nossel on the heat-gun.

author: JimmyJo
author_rank: Contributor
timestamp: February 25, 2022, 11:13:22 am
content: What if you cut down the PCB into 5 smaller pieces each attached to only one pin, then heat it up one at a time.

author: Echo88
author_rank: Frequent Contributor
timestamp: February 25, 2022, 11:34:10 am
content: Thanks for the Adev-graph and teardown of such a Vectron shodan. Always interesting to see what makes them tick. The PIC does the temperature-compensation i suppose?

author: mendip_discovery
author_rank: Super Contributor
timestamp: February 25, 2022, 01:27:05 pm
content: I used a hacksaw and cut the base so I could attack each pin at a time.Almost used the angle grinder.

author: amc184
author_rank: Regular Contributor
timestamp: February 25, 2022, 08:06:24 pm
content: Another option would be to use a solder pot.I've not had to remove an OCXO before, but have used this method to remove physically similar components like PCB mounted transformers. As long as the solder pot is larger enough, you'll get very fast heat transfer to all pins at once, meaning a low risk, low force way to remove it.

author: cdev
author_rank: Super Contributor
timestamp: February 27, 2022, 03:34:07 am
content: 1. ) Use Bismuth alloy desoldering solder. (i.e Chip Quik (TM) ) Its cheap and it does the trick.2. ) Use suction and heat, minimizing mechanical stress.. Also use a clip on heat sink on the pins to minimize the chance of heat damage.I use a small cheap accordion-shaped plastic bellows that I bought on ebay to provide suction thats controlled by my foot, Its connected to a length of tube thats connected to a heavy glass jug with a two holed stopper and some water at the bottom. This acts just like a powered solder sucker that removes all the solder and then its heat (with water) before it can melt the cheap plastic tubing. It cost a lot less than a solder sucking gun and works about as well. It can suck melted solder away in a sustained manner, is what I mean. Without anxiety when desoldering valuable delicate parts.3) preheating to a temperature still too low to cause any melting get it warm and then use regular desoldering tools to raise it the last few degrees. The preheating is to minimize the thermal stress which is what causes the problems.The slow heating and removal with screwdriver pressure seems dangerous to me if it involves an OCXO -one of the most delicate kinds of parts I know of, unless done very very gently, AND using the bismuth alloy stuff. Which changes the characteristics of the solder around the melting point considerably. It also needs to be removed well or else the effect is persistent and subsequent solder bonds may be questionable on that part.An "old" OCXO may be preferable in some respects to a new one because the older they get the slower they age, IMHO. That is true with people too.peace!

author: miro123
author_rank: Frequent Contributor
timestamp: February 27, 2022, 02:30:05 pm
content: Quote from: shodan@micron on February 27, 2022, 01:14:40 amI find SLS polyamide by far the best prototype technology so far.

author: trobbins
author_rank: Frequent Contributor
timestamp: February 27, 2022, 10:12:15 pm
content: Similar to #14, cut a copper plate to just match the pin locations, and solder/wet those locations on the plate, then attach a soldering iron tip to centre of plate and heat to solder melts, then apply pcb to plate so that all pins are in solder blobs and hence heat to same temp. That works great for copper jigs made to heat multipin IC's too.