Nitric Acid and a hotplate - Page 1
Forum section: electronics / general

author: PedroDaGr8
author_rank: Super Contributor
timestamp: May 11, 2013, 01:09:59 am
content: So I was reading around on the internet about how to detect fake transistors. It seemed like in general the fake transistors use an impossibly small die; usually around 3 mm2where the authentic is around 25mm2. It seemed like the common way to open the transistor up was to use mechanical force and take a look at the pad for the transitor. Sometimes the die would stick to the metal side but usually it would either fracture or all you would see was the bonding material.I came across a site that mentioned using 70% Nitric Acid and heat. Interesting...*taps fingers together like an evil villain*. I have 70% Nitric Acid, I have a couple transistors that are dead, I have a chemical hot-plate and I have a fume hood to do this in.Before we go ANY further, I am a trained inorganic/nanotech chemist. I know what I'm doing. If you don't this stuff could easily injure you or worse. The nitric acid off-gases poisonous nitric oxides as it reacts. It sputters mixtures of acid and epoxy. Let alone the acid itself, which is highly concentrated and a huge risk to use. I did this in a chemical fume hood, with the glass down to protect my face. I also had on lab coat, gloves, safety glasses etc. If you don't have the proper training to do this, DON'T!So I get set up, turn the hot plate on, let the transistors sit on the hot-plate for about 10 min (turns out to be way excessive). Put a few drops of concentrated HNO3and it starts bubbling and sputtering but not much change. I keep trying and after about 20 drops I can see some changes.As I worked on them I realized a few things:Cover your hot plate in aluminum foil, it gets messy.If it is bubbling rapidly you are just wasting acid, it should bubble lightly.Add a couple drops, allow it to bubble up and reduce then add another for about 5 total drops.After 5 drops let it bubble almost until evaporated you will see the liquid get dark brown and thicker.Wipe it off with a paper towel at this point.RepeatAll being said, it took a while to do (maybe 20-30 min) and around 20mL of HNO3to eat through the epoxy on the transistor.The end result? The die appears to be exactly 25mm2so its not likely a fake. It also shares a lot of other traits with some of the pics I have seen of TIP35C and TIP36C broken open. Unfortunately, I didn't get all the way through the second one before I ran out of acid.Anyways I think it made for some cool pics.You can clearly see the structure of the die and the bond wires. I eventually mechanically broke off some of the epoxy to show that the metal base and the middle pin are all one continuous piece. In the third from last picture how it was preferentially eating the copper at this point (even eating it out from underneath the transistor die. Also, you can see the one which wasn't finished. The lead wires are just starting to show. Lastly, you can see how harsh the reaction was because the metal parts all used to be shiny.

author: BravoV
author_rank: Super Contributor
timestamp: May 11, 2013, 02:03:02 am
content: Great post, bookmarked, thanks for sharing this.If you had a chance of doing this again, do it at some SOT-XX or TO-92 style plastic body please.

author: c4757p
author_rank: Super Contributor
timestamp: May 11, 2013, 02:05:46 am
content: Awesome pictures. Funny how small the die in a TO-247 looks relative to the package!

author: SgtRock
author_rank: Unknown
timestamp: May 11, 2013, 03:08:12 am
content: Greetings EEVBees:--Real, forensic style, getting to the bottom of it research, with out all the corporate glad handing. Thanks a lot, and please do more."There are two possible outcomes: If the result confirms the hypothesis, then you've made a measurement. If the result is contrary to the hypothesis, then you've made a discovery."Enrico Fermi 1901 1954Best RegardsClear Ether

author: IanB
author_rank: Super Contributor
timestamp: May 11, 2013, 03:20:33 am
content: Quote from: PedroDaGr8 on May 11, 2013, 01:09:59 amQuoteQuoteQuite fascinating, but I'm slightly puzzled. How did you manage to run out of acid after only 20 ml used? Don't labs have bottles of the stuff?

author: IanB
author_rank: Super Contributor
timestamp: May 11, 2013, 03:24:09 am
content: Also, Ithinkit would be a good idea to put the transistors in an evaporating dish or in the bottom of a wide mouthed flask before dripping the acid on them?

author: SeanB
author_rank: Super Contributor
timestamp: May 11, 2013, 06:25:50 am
content: Genuine transistors there. You get some good designs and fascinating geometries in small signal devices especially, where you get star shapes and other shapes as well. Ideally should be done on a disposable pyrex dish, but as the heater pad is ceramic, and anyway will not be harmed by nitric acid much.

author: Skimask
author_rank: Super Contributor
timestamp: May 11, 2013, 07:31:33 am
content: The guys at Sparkfun did something similar to figure out why a batch of chips wasn't performing as expected...https://www.sparkfun.com/news/384

author: Fsck
author_rank: Super Contributor
timestamp: May 11, 2013, 08:11:29 am
content: Quote from: SparkfunI wonder if they realize the difference between fuming and "regular" nitric acid is concentration... The change of naming is a simple dilution.

author: PedroDaGr8
author_rank: Super Contributor
timestamp: May 11, 2013, 08:22:07 am
content: We have the nitric acid around for when we makeaqua regia, which we use to clean the glassware after certain reactions (because its great at dissolving semiconductor materials). I just had a small fraction of a bottle left because recently our focus has been on organic fluorophores which means no need foragua regia. I actually didn't realize how low we had gotten. We have 1.5 bottles of conc HCl left but that does nothing to the epoxy cases (I tried). From this, I gather it needs to be a strong oxidizing acid. So Nitric, Sulfuric, and Chromic would be the big three that should work.As for the use of glassware, a wide mouth flask or beaker is not really practical because of having to constantly wipe off the acid/epoxy slurry. A watch glass, evaporation dish or recrystallization dish would be some what more useful but in general I dislike heating glassware up to high heats with no liquids inside them. I've had some weird shit happen before especially with things that sputter liquid. Mostly spontaneous fragmentation which sometimes doesn't occur until the subsequent reaction (yeah we stress our glassware a bit). Plus you have to clean the glassware, with aluminum foil I can just dispose of it in the solid chemical waste container.

author: PedroDaGr8
author_rank: Super Contributor
timestamp: May 11, 2013, 08:34:08 am
content: Quote from: BravoV on May 11, 2013, 02:03:02 amOh I fully plan on doing this some more. As I get my technique down, I will work on smaller packages. Since I don't use fuming nitric acid it takes longer (though this shows conc. nitric CAN work).Also, in case anyone wonders this is one of the TIP35C that I purchased from TaydaElectronics.

author: free_electron
author_rank: Super Contributor
timestamp: May 11, 2013, 08:39:48 am
content: We have a little spray jst machine to do this kind of work. No mess. Clamp the device in , a nozzle goes up to the device and squirts hot acid on the package ( package is upside down)No acid is squirted on the pins. We get clean etching that way. We can select nitric or sulphuric.I posted a picture of that thing in another thread on the forum already.That way the chips still work , you can still solder them or put them in a socket. We use this for failure analysis or to probe inside the device.It does not eat bondwires or chip material. The device remains fully functional.

author: M. András
author_rank: Super Contributor
timestamp: May 11, 2013, 08:49:02 am
content: those bondwires loook really thin compared to the continous current rating on a normal to247 package

author: G7PSK
author_rank: Super Contributor
timestamp: May 11, 2013, 08:50:14 am
content: I thought that chromic acid was used for cleaning glass. I don't know if this would work on things like transistors but in the past I have used powder blasting ( baking soda)to clean epoxy from metal usually stainless steel this removes the offending epoxy but leaves the metal pretty well intact (a dull sheen finish).

author: peter.mitchell
author_rank: Super Contributor
timestamp: May 11, 2013, 09:50:46 am
content: you could clean glass pretty well with Fluoroantimonic acid, if you used it on one of these ICs you'd probably take out the packaging, bond wires, die and whatever it is on top of and near.

author: Fsck
author_rank: Super Contributor
timestamp: May 11, 2013, 10:04:49 am
content: Quote from: peter.mitchell on May 11, 2013, 09:50:46 amlasering the epoxy off would be a better method than that

author: 4to20Milliamps
author_rank: Regular Contributor
timestamp: May 11, 2013, 03:18:05 pm
content: This link is for educational purposes only:http://books.google.com/books?id=WCQDAAAAMBAJ&pg=RA1-PA238&lpg=RA1-PA238&dq=nitric+acid&source=bl&ots=RN8zCh0cbJ&sig=JaYuyhTKLOESuTi-3IXmxe_BaA0&hl=en&sa=X&ei=xhUjUIHJFoO-9QTQ6IHIDA&ved=0CFEQ6AEwBQ#v=onepage&q&f=true

author: peter.mitchell
author_rank: Super Contributor
timestamp: May 12, 2013, 10:51:53 pm
content: Yeah, sure, I'll heat ammonium nitrate to 200 degrees in my back shed, sounds like a greaaaaaat idea...

author: nitro2k01
author_rank: Frequent Contributor
timestamp: May 13, 2013, 12:45:29 am
content: Quote from: peter.mitchell on May 12, 2013, 10:51:53 pm... said someone at a fertilizer plant in Texas.

author: 4to20Milliamps
author_rank: Regular Contributor
timestamp: May 13, 2013, 03:25:06 am
content: Quote from: peter.mitchell on May 12, 2013, 10:51:53 pmyou fill your car with 20 gallons of highly explosive gasoline but won't heat up a teaspoon of ammonium nitrate? just wear eye protection, and at least you'd go out laughing. Besides it can't be that dangerous they never did dangerous stuff way back when their mom's wouldn't let them.Making nitric acid in small amounts with a spark and bubbling the resultant gas through hydrogen peroxide, for things like gold recovery and whatnot might be handy, unless you have access to the lab grade stuff.

author: peter.mitchell
author_rank: Super Contributor
timestamp: May 13, 2013, 06:30:32 am
content: Quote from: 4to20Milliamps on May 13, 2013, 03:25:06 amNah, I wouldn't fill a car with highly explosive gasoline, I much prefer to ride around on a bike with 1500Wh of Lithium Polymer batteries between my legs

author: PedroDaGr8
author_rank: Super Contributor
timestamp: May 14, 2013, 06:01:03 am
content: Quote from: free_electron on May 11, 2013, 08:39:48 amMust be nice to have, definitely don't have one of those at work. Have a flow cytometer, an HPLC, FPLC, UV-Vis, Fluorimeter, DLS (measures the size of particles in a suspension down to nm sizes) and assorted other lab equipment but nothing that is capable like that. I more just did this because 1) the transistor was already damaged by me and 2) because I could.Quote from: M. András on May 11, 2013, 08:49:02 amKeep in mind those lengths are really short and in an epoxy designed to rapidly transfer heat away. Also, the thinnest one on the right is the base wire, the thicker one on the left is the emitter, while the collector is the middle pin (Which is attached to the body of the device)Quote from: Fsck on May 11, 2013, 10:04:49 amThis is what we call rabbit hunting with a rocket launcher. Personally, I prefer to clean my glassware, not reduce it to pile of goo. Same thing with my limbs (to steal a line from a blog I love, I'd ask all the fluorine chemists to raise a hand but that might be presuming too much about the limb-to-chemist ratio)Quote from: peter.mitchell on May 12, 2013, 10:51:53 pmActually, ammonium nitrate is surprisingly stable. You can burn it, beat on it with a hammer, toss it in your fire pit, etc. Subject it to a shock wave (a laa blasting cap or stick of dynamite) and things go all pear shaped in a hurry. In the case of large amounts of it, it can actually fuse together trapping pockets of hot gas which the pop with enough force to set the ammonium nitrate off.

author: PedroDaGr8
author_rank: Super Contributor
timestamp: February 18, 2014, 12:29:21 am
content: So we got a 4L bottle of conc nitric in. So up first for today's teardown we have an old Harris RFP12N18. It's a rather unremarkable 180V 12A N-channel Power MOSFETSo as usual heat the mosfet up and start adding acid.After a while of adding acid and wiping we can see the bond wires (plus lost a leg)At this point, too much copper was present. The copper catalyzed the break down of the nitric acid. So more drastic measures were needed.Yep I dropped it directly into boiling nitric acid. Those fumes being generated are highly toxic and can kill you. I did this in a fume hood fir safety.After a minute or two the tab is almost gone. Followed by a bit more and start to see the die underneath.Note: The copper nitric solution generated is highly environmentally toxic. It was disposed of in the appropriate acid waste.Anyways, I threw it back in the boiling acid and at last we get this:The left wire is the source, the right the gate. While the backside is the drain. I'm not sure what the purpose of the lines on the back are.Sent from my EVO using Tapatalk

author: PedroDaGr8
author_rank: Super Contributor
timestamp: February 18, 2014, 12:37:15 am
content: Having seen how well doing it in nitric worked. Time for our next test subject! An old 74HC14AP.The case on this dissolved rapidly and became very soft and chunky surprisingly quickly. After about a minute, you can already see the bond wires plus the legs are gone:Unfortunately the bond wires are copper. Plus the die is ridiculously small. Maybe 1-2mm per side. By the time it's done we are left with this tiny gold colored die. Too small to photograph using my cellphone and to tiny to make out any surface detail. Kinda disappointing.You can really see how much room is wasted in a DIP package. My guess is around 95% of the space is wasted space.Sent from my EVO using Tapatalk

author: BravoV
author_rank: Super Contributor
timestamp: February 18, 2014, 01:47:39 am
content: Thank you, keep them coming !How big is that mosfet die ?

author: PedroDaGr8
author_rank: Super Contributor
timestamp: February 18, 2014, 02:25:33 am
content: Quote from: BravoV on February 18, 2014, 01:47:39 amGlad you enjoy them.I'd put it at 4-5mm per side. I think it's still sitting on my bench at work. If so I'll get some more exact measurements for you.Sent from my EVO using Tapatalk

author: BravoV
author_rank: Super Contributor
timestamp: February 18, 2014, 02:35:59 am
content: I know you're a chemist by trade if I'm not mistaken, cmiiw, just curious if Nitric Acid is the only way to dissolve that black substrate ? Is there any other acid that can eat through that black plastic without affecting any metals ? Maybe other organic acid ?Again, I don't have any idea what I'm talking about, its just really intrigued to see if you can just dissolve leaving the whole die + all metals (copper+nickel etc) intact, is it possible ?Edit : As a "nanomaterials" chemist (from ->Your post here), that sounds really impressive at least to me, don't you think its time to show off a bit ? Please ?

author: Tinkerer
author_rank: Frequent Contributor
timestamp: February 18, 2014, 03:11:00 am
content: Wow, they really do waste alot of space.Would be interesting to see a chip that was a bit more complex.

author: PedroDaGr8
author_rank: Super Contributor
timestamp: February 18, 2014, 03:41:49 am
content: Quote from: BravoV on February 18, 2014, 02:35:59 amUnfortunately, I don't think there are any that will dissolve the epoxy and leave the copper intact. To dissolve the epoxy, you need a strong oxidizing acid such as Nitric, Sulfuric, Chromic , etc. I strongly doubt any organic acids would be strong enough and if they are they would likely chelate the copper very nicely.As for showing off, sure. I love showing offThe materials I make are called fluorescent quantum dots. They are highly fluorescent tiny nanocrystals of semiconductor materials. Usually on the order of 2-20nm in size. The color is almost entirely size dependent with the smaller the crystal the bluer the emission.Two vials sitting in sunlight:A bunch of colors sitting on a blacklight. Yes I have a blacklight in my fume hood.Tubes of materials:Materials in an ultracentrifuge tube. The ultracentrifuge can spin at up to 80000 rpm. Though we don't hit quite that high.Recognize the hot plateThe finished materials from the previous image:Hopefully you enjoyed those images.Sent from my EVO using Tapatalk

author: PedroDaGr8
author_rank: Super Contributor
timestamp: February 18, 2014, 07:37:21 am
content: Quote from: Tinkerer on February 18, 2014, 03:11:00 amAt some point I plan on it. I want to open up a few op amps, voltage regulator, more transistors, etc. All in my free time.Sent from my EVO using Tapatalk

author: BravoV
author_rank: Super Contributor
timestamp: February 18, 2014, 10:06:56 am
content: Quote from: PedroDaGr8 on February 18, 2014, 03:41:49 amThanks a lot, looks like a really fun place to work with.Coming from non applied science education background, I drolled real hard everytimes seeing stuffs like these.

author: PedroDaGr8
author_rank: Super Contributor
timestamp: February 18, 2014, 05:47:11 pm
content: Quote from: BravoV on February 18, 2014, 10:06:56 amThanks, yeah I really enjoy it.Also, measured the die today. It's a smidge over 4mm per side (call it 4.2mm)

author: SeanB
author_rank: Super Contributor
timestamp: February 18, 2014, 08:07:51 pm
content: Best chips to do are processor chips, or any multipin QFP package. If you have a dead cellphone, look to see if you can find any multichip modules inside and decap them.

author: con-f-use
author_rank: Unknown
timestamp: February 18, 2014, 08:52:38 pm
content: Just wanted to say: Thanks for sharing! Awesome!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 19, 2014, 12:01:43 am
content: Cool!...Well, hot.I'd get some nitric acid myself, if I had the facility to handle it. I am learned in the ways of chemistry, but this apartment isn't very amenable to the practice thereof.The "poor man's" method I've used for my last few destructive tests were simply pinching the TO-220 package with pliers... the plastic shears off the metal backing. If it failed catastrophically, it usually breaks along the cavity (formed by arc erosion and rapidly expanding gasses), otherwise the chip itself is usually fractured so that about half comes off with the plastic.The last two of interest I did were a Fairchild FQP6N40C (linear power dissipation test, failed almost exactly at datasheet ratings) and Vishay/Siliconix IRF740PBF. The former has a small die, typical for modern processes; the latter has a surprisingly large die (3.8 x 5.1mm), which probably explains its failure well past datasheet ratings (either Tj was some 210C when it finally went, or RthJC was less than half the maximum rating!). The IRF740PBF is slightly more expensive, but for the amount of silicon inside... I really wonder if there is any other product that even contains so much high-purity silicon for so cheap? (Solar panels maybe, but even single-crystal types will be the dregs, probably not the purity required to build a functional MOSFET.)Tim

author: IanB
author_rank: Super Contributor
timestamp: March 22, 2014, 11:58:21 pm
content: Quote from: BravoV on February 18, 2014, 02:35:59 amUnfortunately, "without affecting any metals" does not come with the package. A strong oxidizing acid that can dissolve the epoxy will dissolve most metals it encounters as well. Maybe only gold will survive such aggressive treatment.One of the hardest problems in chemistry is to "dissolve this, while not dissolving that".

author: XOIIO
author_rank: Super Contributor
timestamp: March 23, 2014, 12:44:33 am
content: Have you done an lm7805 or similar? I agree these to-247s look really tiny lol

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 23, 2014, 01:23:48 am
content: Oddly enough, aluminum is resistant to nitric, hence why a decapped die still functions.A number of metals are resistant to pure fluorine, like plain old iron.Tim

author: SeanB
author_rank: Super Contributor
timestamp: March 23, 2014, 09:19:56 am
content: Fluorine resistance is mostly a function of forming a compound on the surface that is both well bonded, hard and similar in ionic radius, so it does not spall off. Nickel as well does that, but I still regard any strong oxidising agents as dangerous when concentrated.Aluminium is incredibly reactive and burns well once you break the oxide layer. Just a single drop of Mercury metal or Gallium metal will destroy a large block of Aluminium in a few weeks if left alone.