best breakproof potting compound - Page 1
Forum section: electronics / projects

author: Simon
author_rank: Unknown
timestamp: October 09, 2014, 09:25:52 am
content: We are shipping a one off prototype to a customer, small pcb in a plastic enclosure, we want to make as sure as possible that they don't try to get into it and copy it. Any recommendations on the worst potting compound to try and break into ?

author: timb
author_rank: Super Contributor
timestamp: October 09, 2014, 09:32:36 am
content: Cement.Sent from my Smartphone

author: Simon
author_rank: Unknown
timestamp: October 09, 2014, 09:33:40 am
content: Err I think cement will happily break up and fall away nicely making it very easy to see what is inside.

author: timb
author_rank: Super Contributor
timestamp: October 09, 2014, 09:44:04 am
content: No, I mean you fill buckets with the cement, along with your client's feet. Then you push them off a pier.This guarantees they will never divulge *any* of your secrets.Sent from my Smartphone

author: Simon
author_rank: Unknown
timestamp: October 09, 2014, 09:49:28 am
content: Slight problem with that plan, they won't be buying thousands of the things after thatI have spoken to a potting company, the recommendation is STYCAST2850FT with a CAT11 catalyst, apparently even diamond drills fail

author: Kjelt
author_rank: Super Contributor
timestamp: October 09, 2014, 09:52:47 am
content: Ah you already have your answer then, I would have suggested epoxy mixed with some dust of a very hard material (hardest you can afford), diamonddust, or sand from selected source.But if they want too they can break anything even thought about xraying the darn thing?What I should do is put in the contract that they do not own the prototype and that they return the delivered item in good condition meaning not been opened or broken

author: mcinque
author_rank: Unknown
timestamp: October 09, 2014, 11:42:37 am
content: Quote from: Simon on October 09, 2014, 09:49:28 amNot because it's hard. If (sintetic) diamond drills fails, is because they are not the right tool. The compound is NOT granite hard so it cloggle the diamonds.The only way to beat diamond drills (if they not cloggle) is to attack the way the sintetic diamonds are sticked to the drill: that is a particular glue that cannot resist to heavy temperatures (600°C and over).IMO you need something like the epoxy used in sealed transformers mixed with a little bit of dark powder.

author: amyk
author_rank: Super Contributor
timestamp: October 09, 2014, 12:21:33 pm
content: I bet that epoxy won't stand a chance against concentrated nitric acid...Quote from: Kjelt on October 09, 2014, 09:52:47 amI agree with this. You can't stop anyone who is determined enough to reverse-engineer it. (Speaking from personal experience.)

author: Simon
author_rank: Unknown
timestamp: October 09, 2014, 01:14:22 pm
content: in actual fact the thing is that simple it's not worth trying to reverse engineer, why my employer is so bothered is just down to them thinking it's so clever, it would be faster to redesign the thing.

author: SArepairman
author_rank: Frequent Contributor
timestamp: October 09, 2014, 06:09:02 pm
content: ya they can put it in nitric acid lol

author: rob77
author_rank: Super Contributor
timestamp: October 09, 2014, 06:26:53 pm
content: any epoxy (suitable for the temperature range of the product) mixed with a very fine grain sand will do the trick - i used to do it that way. it's hard to machine - because of the sand (it kills regular drill bits or saw blades quite quickly ) and it's not transparent - again thanks to the sand.

author: SeanB
author_rank: Super Contributor
timestamp: October 09, 2014, 06:40:36 pm
content: So you use the styrocast ( that stuff looks impressive, strong, hard and resistant to almost anything aside from blowtorches and strong acids) and use some fine and coarse silica sand ( preferably a washed and graded sand, not your bog standard building sand) with a big vacuum degassing chamber to degas the epoxy sand mix prior to potting, then an overnight 80C cure afterwards. Tip for the degassing chamber is to use a refrigerant drier ( preferably a bloody big one with a replaceable core and a fine particle filter as well) on the line to the vacuum pump to act as a filter to remove the inevitable sucking of epoxy into the suction line. That way you only have a filter to replace and a short line to do as well, not an entire expensive vacuum pump. If you do not mind voids then do not degas and accept that you will have bubbles in the cured product.

author: plesa
author_rank: Frequent Contributor
timestamp: October 09, 2014, 06:45:44 pm
content: It is really difficult to protect IP. To be honest it must be destroyed when someone needs to break some protection. There are only bad choices as far as I know.You can protect it with potting, but this will not prevent copying, you also cannot fully controls people familiar with your design.So I suppose that nowadays it is only about the putting things on market really fast.

author: rob77
author_rank: Super Contributor
timestamp: October 09, 2014, 08:05:17 pm
content: Quote from: SeanB on October 09, 2014, 06:40:36 pmor mix the sand in advance with only single component of the epoxy, and mix the second component of the epoxy prior to usage. this way you don't have to degas with vacuum - the bubbles will have enough time to go away (ok. not all of them, but most of them will go away)

author: rob77
author_rank: Super Contributor
timestamp: October 09, 2014, 08:10:08 pm
content: Quote from: plesa on October 09, 2014, 06:45:44 pmyes it's difficult to protect, and everyone knows there is no 100% protectionbut the main goal is to make the copy difficult, actually make it as difficult as designing a new product. once the competitor has to design the product from scratch, then it's regular competition, not stealing

author: Simon
author_rank: Unknown
timestamp: October 09, 2014, 09:29:33 pm
content: It's really not worth copying, the idea is worth more than the design time and IP

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 10, 2014, 01:14:24 am
content: Find a new customer. If they're that stupid and/or shitty, you don't want their business.If your employer disagrees, find a new employer for the same logic.Tim

author: calexanian
author_rank: Super Contributor
timestamp: October 10, 2014, 02:15:01 am
content: Quote from: T3sl4co1l on October 10, 2014, 01:14:24 amAgreed. A good electronic epoxy will actually retain a small measure of flexibility because a bar setting epoxy will spear parts off a board the. Temps start changing. Different temp co' of expansion.

author: Simon
author_rank: Unknown
timestamp: October 10, 2014, 05:56:04 am
content: Quote from: T3sl4co1l on October 10, 2014, 01:14:24 amI take it you don't work in a niche market (employer and customer) with no qualifications and just starting to make something of it.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 10, 2014, 06:02:16 am
content: I know a few people whose business could be described that way, but they don't ask for obscurity.If it's so easy to copy, your company must be asking too much on the price. (Sounds like a supply issue? Maybe your employer has problems with quoting figures? Maybe shades of the original supposition? Idunno.)Tim

author: Simon
author_rank: Unknown
timestamp: October 10, 2014, 06:12:30 am
content: They are a mechanical company and I designed this in my spare time as i saw a "gap" for an electronic system, they showed it to a supplier who's kit it is designed to work with (despite my warning they would only resell it to competitors if they bought it) and now one of those competitors is very interested so they are just a little concerned they will be trying to copy it. I think the price is about right (in fact the level of interest shows that it's quite a good price), it's just that we (I) have hit on a really good idea because I realized they were overestimating the cost and underestimating the value of adding a little bit of electronics to their main kit so i did it and demonstrated it and a whole new world suddenly opened up for them.Bearing in mind the guy that is now championing this spent all the time i spent developing it telling me I was wasting my time and acting like it would have to work on steam if it was going to work and be cheap. So i put the whole package together with complete assembled quote price slapped it on his desk and now he's holding onto it for dear life. It's a good little earner in itself and very good added value to existing kit.

author: Rerouter
author_rank: Super Contributor
timestamp: October 10, 2014, 07:03:54 am
content: Coat it in lacquer, then in JB weld metal epoxy, It is possible to break into by soaking in mentholated spirits for an hour, scape off a few softened microns, then repeat, but if you make it thick and they still go to the effort of cloning it, you could encase it in anything and they would still get it eventually, JB weld is just one of the best deterrents i know, seeing as i had to reverse engineer something encased in a thin layer of it, if it was more than 2mm thick i would have given up and rebuilt based on functionality,

author: mzzj
author_rank: Super Contributor
timestamp: October 10, 2014, 01:36:45 pm
content: Quote from: T3sl4co1l on October 10, 2014, 01:14:24 amisn't this pretty mich "standard" project for Simon?Just wait a day or two and he will tell that his boss wants it to work in liquid nitrogen while proplled by 120mm mortar to the sky.If you want to make copycats work for their bread go creative and mine your prototype. :d-shorted zeners and diodes for jumper wires-open circuited failed resistors for no real functionality. In series with plenty of tantalum capacitor that will go flames if failed resistor is replaced with working one.- shorted mosfets.- vgs-th matched mosfets in a senseless ugly design that wont work without matching components.- logic chips or microcontrollers with some of the inputs "zapped" permanently to either ground or vcc. :d

author: Simon
author_rank: Unknown
timestamp: October 10, 2014, 03:43:38 pm
content: Quote from: mzzj on October 10, 2014, 01:36:45 pmShit i nearly forgot that myselfThis started as my own simple little thing that I cooked up from scratch and was going to deliver as my own creation. Now they have done the usual and trying to complicate matters, we are talking about something that comes standard potted fully assembled for £15-17....QuoteIt's 1 reg, 1 mcu, 1 output signal mosfet and related caps and resistors, it hardly bears trying to copy and trying to complicate it with decoys will double it's size and cost

author: mzzj
author_rank: Super Contributor
timestamp: October 10, 2014, 04:28:36 pm
content: Quote from: Simon on October 10, 2014, 03:43:38 pmWell, then you can sell it with twice as big price tag

author: Simon
author_rank: Unknown
timestamp: October 10, 2014, 04:44:19 pm
content: Quote from: mzzj on October 10, 2014, 04:28:36 pmIf the price is right it won't be worth them going through the hassle of reverse engineering it and setting up their own manufacturing of it, far easier to contact us and let us handle it. If we increase the price then it may be worth their while. Selling price should be 30ish

author: wiss
author_rank: Frequent Contributor
timestamp: October 10, 2014, 05:56:11 pm
content: What about fibres that jams a drill bit? Thick layer of fibreglass around the board and then epoxy?

author: SeanB
author_rank: Super Contributor
timestamp: October 10, 2014, 06:59:38 pm
content: Granite or ceramic sand does a number on drill bits quite quickly. No need to use fibres, unless you add short strand chopped aramid fibre ( kevlar cloth) for added rigidity between a inner flexible potting compound and a rigid exterior potting. If you really want to fool them blow a few diodes open circuit and add across power rails.If you are really anal a fine grid of insulated copper wire scramble wound around it consisting of 6 strands to assorted pads where they supply power, ground, sinals and no connects will defeat most depotting methods. Used in the bank crypto modules for that purpose, though there it also has the keep alive circuitry power through it.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 10, 2014, 07:12:55 pm
content: Ask IBM how they do it.http://www-03.ibm.com/security/cryptocards/pcixcc/overhardware.shtml

author: wagon
author_rank: Frequent Contributor
timestamp: October 11, 2014, 12:01:19 pm
content: Scrap the numbers off the chips, too.

author: wagon
author_rank: Frequent Contributor
timestamp: October 11, 2014, 12:10:35 pm
content: 'Back in the day' I reverse-engineered the serial number & copy count 'chip' on various colour photocopiers. I eventually made & sold a product that read them & enabled them to be 'reset'. I used a normal serial eeprom programmer with a 'do nothing' box in the wiring harness. The do nothing box did do something, but it was enough to confuse any potential copiers.

author: electronic_eel
author_rank: Regular Contributor
timestamp: October 13, 2014, 07:43:37 pm
content: Make sure your device still works after potting it and going through a few thermal cycles.If your potting compound is too hard and has a slightly different coefficient of thermal expansion than your board, the potting compound will rip you the components right off the board.I learned that the hard way when I was trying to protect some electronics for outdoor use. In winter the parts broke, one by one.

author: SL4P
author_rank: Super Contributor
timestamp: October 13, 2014, 11:51:21 pm
content: Pretentiously Posting Polysyllabic ProseHe said it not me.

author: timb
author_rank: Super Contributor
timestamp: October 14, 2014, 09:42:27 am
content: Quote from: SL4P on October 13, 2014, 11:51:21 pmHahahaha, what?Sent from my Smartphone