Goop Removal Theory Topic

[finkfloyd]

Hi,

I know someone who has a pedal, covered in goop, and asked me the best way to remove it, I dont know which/what pedal it is.

I have said ive never had a pedal covered in goop, so i dont know, but i would probably try to prise it off, or use something like a dremel to cut down level to the board and prise it off..Ive heard you can xray it.


Anyway does anyone know any methods on removing this goop?

Also If anything like a resistor or cap blown , when this goop is on there, surely you need to know how to fix it.

[Peter Snowberg]

It depends on the goop used. for "removing goop".

Most of the time, prying will destroy at least some of the components

If the pedal is in current production, please don't post the circuit. Thanks.

[tiges_ tendres]

this has been brought up before here.  the dremmel sounds like a terrible solution! please dont try that.

I've heard of a screw pushed into a soldering iron works.  Never tried it though, as the only goop that winds up on my pedals is through negligence rather than prevention of cloning!

[Mark Hammer]

Most things that have been liquid at some point will become softer when a bit of heat is applied.  It needn't be extreme heat.  I imagine hair dryers can even work in some instances, though in other instancs more severe heat is required, depending on the material.

[R.G.]

There are different goops. Epoxy and polyester are the most common ones because they're least expensive. Urethanes are also used, but are expensive and difficult to use, as they are modestly toxic before curing.

I have had really good luck with the following.
1. Get a soldering iron with a screw-in tip. I got one at Radio Shack, about 40-50W.

2. Go to a hardware store and get a machine screw that screws neatly and tidily into the soldering iron. Stainless steel is nice.

3. Grind the head off the screw and grind the remaining screw into a flat chisel point. A razor sharp edge is not needed or advisable. Just a thin front edge that won't quite cut you.

4. Heat the iron up and use the chisel point to slowly heat/scrape the goo off.

Using heat guns can soften goops all right, but be very careful, because the flame temperature of some goops is near the melt temperature, you could start a fire pretty easily with a paint removal heat gun. I've never had any luck with hair dryers. Propane torches are out, obviously.

5. Dremel and other abrasives are out. Too much damage to the underlying circuit.

6. Chemicals work - slowly, expensively, and at hazard to your life and lungs. Acetone dissolves cured expoxy .... s...l...o...w...l...y . Red fuming nitric works, but who knows what will be left to reverse? Urethanes are proof against most chemicals. 

By the way - PCB stock is glass-EPOXY,  parts are given EPOXY conformal coatings, ICs have bodies that are cast from EPOXY so you have to be careful what you're removing.

The part epoxy is usually harder than the goop, but you understand the problem.

[A.S.P.]

it`s always good to know the weapons used by the opposite parties... 

[Paul Marossy]

By the way - PCB stock is glass-EPOXY,  parts are given EPOXY conformal coatings, ICs have bodies that are cast from EPOXY so you have to be careful what you're removing

And, therefore, acetone is out... right?

[A.S.P.]

what was that ceramic/stone/cement-like (fragile) stuff they made ICs of,
back in the 70`s ??

[amz-fx]

I bought a boutique pedal a few months back. It had extra goop because the builder knew it was for me.     I played it for a few days and then decided to look into it to see what was making it sound so crappy      The board was totally glued in place.

I noticed the goop seemed to be fairly brittle...  so I put it into the freezer and when it came out, the goop was like crackers and flaked right off!  Another mystery solved...

A good goop removal technique is to get some thick paint remover gel that contains methylene chloride and methanol.    Slop it on with a brush and let the board soak.  The goop will usually come right off.

regards, Jack

[cd]

OK what about JB Weld.  The maker says the only way to get it off is by grinding or filing, or heating above 600F, and it withstands -67F cold.

[Connoisseur of Distortion]

600F doesn't seem impossible at all... 

[R.G.]

OK what about JB Weld.  The maker says the only way to get it off is by grinding or filing, or heating above 600F, and it withstands -67F cold.

The settings on my controlled temperature soldering station run up to 850F.

300C is the nominal melting point for many electronic solders. That's 572F. Soldering irons have to get hotter.

I noticed the goop seemed to be fairly brittle...  so I put it into the freezer and when it came out, the goop was like crackers and flaked right off!  Another mystery solved...

I was not that patient. I used dry ice in a cardboard box. The brittle ones do seem to pop off under temperature cycling. I think it's a lack of proper priming of the components before gooping.

A good goop removal technique is to get some thick paint remover gel that contains methylene chloride and methanol.

I once ate the color bands off some resistors that way. Had to measure every stinking resistor. PITA.

As a practical matter, the cost of hiding something inside goop goes up a lot if you're trying to protect against anything but a top and bottom side scanner. It can easily exceed the cost of the circuit board you're protecting if you do a good job. That makes almost every hider give up on more effective means of hiding.

Potting compounds are not all that benign, either. There are otherwise good potting compounds that give out corrosive gasses during curing. Polyester and epoxies are exothermic, so if you get them too deep in one pour, they can overheat and damage the circuit. If the potting gook has a significant shrinkage on curing, it can break solder joints and fragile components. Good potting is an precision technique.

The guys who want to crack satellite TV decoders get rough. They use red fuming nitric acid to dissolve away the top side epoxy encapsulant on surface mount flash microcontrollers, and them use microprobes to break the protection latch inside the chip so they can read out the decode algorithms.

We play in a sand box compared to the big boys... 

[amz-fx]

The guys who want to crack satellite TV decoders get rough. They use red fuming nitric acid to dissolve away the top side epoxy encapsulant on surface mount flash microcontrollers, and them use microprobes to break the protection latch inside the chip so they can read out the decode algorithms.

We play in a sand box compared to the big boys...

It is actually not that expensive to hire that done....   seems like it was around $25 per chip as I recall.  I've got one of those companies  bookmarked in case I ever feel  the need for their services!   

regards, Jack

[gez]

I know someone who has a pedal, covered in goop, and asked me the best way to remove it, I dont know which/what pedal it is.

Yeah 'someone'...and your 'friend' has an itch down below you say? 

[kusi]

hi,

i use only a headgun, plier, tweezers and loooots of patience! with this, i removed some of the hardest goop i`ve ever seen in pedals.
ok, the PCB and all components was broken after removing the goop, so i had to desing a new PCB. 

mfg kusi

here some pics of pedals without the goop
http://forum.musikding.de/yabbse/index.php?topic=4552.0
http://forum.musikding.de/yabbse/index.php?topic=1711.msg61236#msg61236

(you have to login!)

[Dirk_Hendrik]

it`s always good to know the weapons used by the opposite parties... 

We've been here before haven't we

Again, concluding;
If the finanicial value of the item is of no direct concern for the hacker gooping is not an option. It won't keep the determined hacker away. I experience the attempt to goop circuits more as a challenge than as a drawback.

Same goes for sanding the chips and forgetting the bottom part. In the first case I ran into the type number was part of the production number on the bottom of the case. In the 2nd case it wasn't but the number was so familiar that a call to one of my suppliers was enough for confirmation and a main to the manufacturer enough to tell me the type number, production date and time , production line, country of manufacturing, freight forwarder, case and pallet ID, etc etc.