Salvaging and "renew" an IC - Page 1
Forum section: electronics / general

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: August 09, 2020, 08:01:12 pm
content: I have several hundred (could get into thousands, maybe) SOIC-16 chips that I need to salvage and then re-use. They will be placed by a PnP machine, and regular reflow. Basically, once removed and "prepped", used like a new chip would be. These chips are obsolete & unobtainable, can't just buy new.Here is the situation:They are covered in a mix of silicone and urethane conformal coatings. I cannot see through the silicone conformal coating as it is very thick and appears colored, and causes mounting/reflow issues. This coating needs to come off. I've used some spray on conformal coating remover "for silicone" with zero results.Sometimes the pads from the old PCBs come with and get stuck onto the chip. I am using IR heat from the bottom of the board to remove these chips (the PCBs are shot, not reused), and sometimes form solder bridges during removal, somehow.My goals:Need to remove the silicone conformal coating. The urethane coating can stay on.Need to clean the contacts of the ICs. Open to ideas on this one. I have been doing it by hand so far, and it is slow and tedious.Basically, how do the "new" used chips from China et al appear new? What methods do they use, and can they be utilized in a smaller operation?

author: Tomorokoshi
author_rank: Super Contributor
timestamp: August 09, 2020, 09:14:51 pm
content: Have you tried anything like these:https://www.dow.com/en-us/pdp.dowsil-ds-2025-silicone-cleaning-solvent.04089120h.htmlhttps://siliconesolutions.com/silicone-remover.htmlAs suggested in the datasheets for these before using a chemical method it may be best to consult with the manufacturer. Test against other SOIC parts to see what happens to the plating, package, labeling, and leftover acrylic coating.Silicone conformal coatings are likely one of these:https://www.dow.com/en-us/search.html?x11=category&q11=products&x54=industry&q54=Electronics&step=industry&q=conformal%20coating&t_s=1597006782079&tab=productsThere may be guidance in some of the documents for how to remove the cured material.For the cost and the amount of work going into reclaiming the parts, it may be best to skip the PnP machine and install them by hand. The alignment of the pins, plating issues, etc. may require some careful attention anyway.

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: August 09, 2020, 10:55:05 pm
content: Quote from: Tomorokoshi on August 09, 2020, 09:14:51 pmOrdered up some of the Dow silicone remover, see how that does.I'm REALLY hoping to not have to solder by hand. Even if I have to hand place them (what I am doing now), I REALLY don't want to take the time to hand solder.I think I'll try attacking the silicone with a brass brush before the ICs are removed. Still doesn't solve the issue of pads lifting, but one problem at a time I guess...Need something akin to a desktop HASL machien. That should clean up the contacts wonderfully.

author: coppercone2
author_rank: Super Contributor
timestamp: August 10, 2020, 12:49:02 am
content: build a special small fixture so you can put the chips on it one by one and carefully scrape them at convenient angles (ball joint micro vise).You might want to get a micro chisel or carefully cut a exacto chisel blade to the right size and shape.

author: KL27x
author_rank: Super Contributor
timestamp: August 10, 2020, 01:54:42 am
content: ^+1. Step 1. mechanical removal of bulk materialThen you do the solvents plus brushing.Finish with solvents and something to absorb/adhere/collect any undissolved particulates. Sawdust, paper towels, something.Then rinse and blot dry.

author: BrianHG
author_rank: Super Contributor
timestamp: August 10, 2020, 02:04:15 am
content: Which ICs are unobtainable?

author: coppercone2
author_rank: Super Contributor
timestamp: August 10, 2020, 02:25:12 am
content: at 1000 quantity I would think it might even make more sense to build a 'array' of fixtures for the chip to go through, so you are not repositioning stuff all the time. You can even make tiny 'blade guards' to protect the chip leads for top and bottom cleaning, most of the way, so you can be a bit less careful doing the 'bulk' of the work.Keep in mind, those weird solvents might be meant for doing diagnostics work, to analyze IC's and stuff that are suspicious. It might not work well with the plastic and cause the chips to become less reliable. I don't think its designed to 'redo' a botched assembly line. Cleaning chip leads is likely going to be magnified work with scrapers/hooks. The last thing you want to do is deep soaks with chemicals. On the other hand, it might result in less mechanical strain on the IC leads, if you are working with chemically weakened stuff.*new chip from china is often NOT reliable. Run hot etc. There is a difference between cleaning for sale and cleaning for function. For instance, I could dip a rusty gear box into HCl, and paint it, but its not going to result in a happy customer.You might want to consider doing a board redesign. Personally, I think if something needed to be potted, for reasons of reliability, reusing chips put through non standard processes is a BAD IDEA. Small traceable repair work.. ok. Mass production with these methods? Ehhhhhhhhhhhhhhhhhhhhdo you feel lucky? In my opinion, E-waste bin needs to be filled up. I don't think people like to hear 'we do it like china' in a sales pitch.

author: magic
author_rank: Super Contributor
timestamp: August 10, 2020, 07:19:44 am
content: Dunno about your coatings, but for crap stuck to the leads I would try the following process (and I think this is what the Chinese use)Stir in a cup of molten solder to remove metal debris.Somehow remove solder bridges. I think chances are they won't form in the first place if you keep rosin flux floating on your solder pool.Drop in IPA or acetone bath for a while to get rid of flux residue.Quote from: BrianHG on August 10, 2020, 02:04:15 amAlmost all of them

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: August 10, 2020, 03:20:59 pm
content: Quote from: coppercone2 on August 10, 2020, 02:25:12 amI don't disagree with any of your points, but the IC is not readily replaceable, even with a package change. I would have to either get a custom IC designed and made or do a COMPLETE redesign of the entire PCB strategy. Neither is preferable, obviously, though the latter may be what I end up doing.The ICs are old, custom(ized) high voltage solenoid drivers that runs on TTL activation. So far, I have yet to find a compatible IC, even in a different package, despite multiple searches. The closest I've found is a Bosch IC, but it would take a micro to translate the TTL to the comm protocol it uses. Theoretically possible of course, but what a PITA.

author: BrianHG
author_rank: Super Contributor
timestamp: August 11, 2020, 12:25:14 am
content: Quote from: Rat_Patrol on August 10, 2020, 03:20:59 pmOk. Sure.

author: coppercone2
author_rank: Super Contributor
timestamp: August 11, 2020, 12:29:22 am
content: I do like the idea of that chip being a good solution to the drive the solenoids. IMO a sign of good quality, and possibly reliability, but you might lose that feature if you mess with the chips using weird chemicals.Solenoids are pretty important devices, you don't want them misfiring.I take it you tried this ?https://www.ti.com/motor-drivers/solenoid/products.htmlthis one being the basis for most of them IIRChttps://www.ti.com/lit/ds/symlink/drv110.pdf?ts=1597106361289&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FDRV110Keep in mind you might be able to add a feature with a new chip, did you consider trigger and hold currents in the previous design? It is possible to save power and increase solenoid life time by using a chip that can trigger the solenoid then reduce the current to keep it open with less heat (but it might effect vibration resistance some what). I saw these features advertised by Ti for electromechanical drivers. Actually a nice feature.. you would be surprised how hot those valves can get if you never actually worked with one... and if you ever had a dishwasher break on you, you know how fucking smelly it could be.And, with modern electronics being better at handling higher currents, you can also consider swapping solenoids to lower voltage higher current ones with little consequence other then wire gauge increase.

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: August 11, 2020, 02:25:34 pm
content: Quote from: coppercone2 on August 11, 2020, 12:29:22 amThe biggest issue with finding a replacement is the 100v DC boost voltage with high/low mosfets to control. The Bosch driver I found will work, but it will take that translation micro, but that probably wouldn't be the worst thing. This isn't my PCB design, I was approached to produce new boards for these old machines. I have the PCB schematics, but I do not have access to any of the software builders for the micros that are on the board already, so I have to tip toe around messing with operations of the current 2 micros.As far as the current drivers, even on the PCB schematic they are labeled ASIC, and have a custom part number. New units are just not available.

author: coppercone2
author_rank: Super Contributor
timestamp: August 11, 2020, 11:47:48 pm
content: 100vdc is a bit hit for solenoids I think??

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 12, 2020, 01:35:58 am
content: Why would anyone make an ASIC for what can be done with MOSFET pairs cascoded on top of ULN2003s..?Tim

author: coppercone2
author_rank: Super Contributor
timestamp: August 12, 2020, 01:48:46 am
content: Quote from: T3sl4co1l on August 12, 2020, 01:35:58 amsmaller, neater

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: August 12, 2020, 02:27:35 pm
content: Quote from: coppercone2 on August 11, 2020, 11:47:48 pm100vdc boost to open, then they drop down to 24vdc hold voltage.They work just like a large fuel injector, and I think the IC they originally used WAS a modified fuel injector IC.

author: coppercone2
author_rank: Super Contributor
timestamp: August 12, 2020, 11:58:56 pm
content: if this is automotive environment, you might have even more cautions about reusing the chips. They will take extra hard abuse here.maybe the old company has masks? hidden away in a corporate archive some where so they can restart production at a slightly reduced cost? never know if tooling was kept.. some people just keep old stuff in case this happens. Never know..

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: August 13, 2020, 05:29:55 pm
content: Quote from: coppercone2 on August 12, 2020, 11:58:56 pmOriginally made by Motorola. I actually went down that rabbit hole, and between "we don't have it" and "custom IC, we won't do it", that just isn't a possibility.I think that the Bosch IC that I found may be a good option. It won't take much of a micro (or code) to translate the on/off signals from the primary processor to whatever protocol the Bosch uses.

author: coppercone2
author_rank: Super Contributor
timestamp: August 14, 2020, 02:22:05 am
content: how about repackaging ? maybe you can have them repacked in new plastic with new wire bonds for some modest sum?Not actually sure how well a rebonded IC works. Maybe tthe chip has a excess of material on the bond pads so you can use a high end micromachining CNC to strip the old metal and reweld it... or deposit more metal on itNot sure if you would need to laser remove the old wire or if they have machinery to mechanically mill it out (I saw something in a youtube video with a nasa 'finishing' machine that had insane specifications).