Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Steve,

I didn't want to mention MEK. This is bad stuff. Our company used it in the shop to clean up epoxy spills and the like. A respirator or aggressive ventilation system is a must. It is highly flammable, and is directly absorbed through the skin. Apparently, it is a neurotoxin. Definitely something to stay away from.

 

Hi Harvey

Great info, thanks. With more stuff out there being designed not to be
fixed, and thrown away, I had always wanted to
know more about the possibilities.

I remember when I worked in the Aerospace industry, the painter at our plant
carried MEK / Methyl Ethyl Keotene
around in ample supply, and some of that on a cloth woould pretty much take
the paint right off the surface of an
airplane no problem.

I remember it was not very pleasant at all to smell and it had a pretty high
hazmat rating sticker on it and he did not
leave that container open unless he was using it. He was suppose to wear a
respirator also if I remember right.

I got the impression that stuff would dissolve most anything even maybe
tough epoxy but never tried it.

Steve Hearns
Technotronic Dimensions, VT [USA]
WWW.TECHNOTRONIC-DIMENSIONS.COM
1.518.663.3421 (MAIN)
1-877-817-9885 (Voice / Fax Toll Free - US Only)
E-Mail: Steve@...
--
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----- Original Message -----
From: "Harvey Altstadter hrconsult@... [Homebrew_PCBs]"
<Homebrew_PCBs@yahoogroups.com>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, July 04, 2017 12:40 AM
Subject: Re: [Homebrew_PCBs] Ferric chloride staining PCB substrate

> Steve,
>
> With regard to dissolving epoxy, I have good news, and I have bad news.
> The good news is that there are chemicals used for depotting
> encapsulated assemblies.
>
> Back in the days before dirt was invented, I ran a failure analysis lab
> for my employer where my technicians used several chemicals from
> Dynaloy. They were sold under the Dynasolve product line. We also used
> another product of theirs called Decap. Here is a website for one of
> their distributors: http://www.ellsworthadhesives.ca/manufacturer/dynaloy
>
> I note that they now have a greater variety of chemicals than were
> available "way back then."
>
> That being said, there are a few issues (the bad news):
>
> 1. The chemicals don't dissolve the epoxy. They swell the epoxy and
> cause it to flake off. Active removal (scraping) is required
>
> 2. I think we had to match the chemical to the epoxy cure system, i.e.
> amine, phenol, etc., to get the best performance. I don't know if this
> is more or less so now, with the greater number of chemicals available
> today.
>
> 3. Since the circuit boards are usually epoxy impregnated, they will
> suffer as a result of this treatment. Any other parts that are epoxy
> encapsulated, or made with certain plastics would likely be adversely
> affected.
>
> 4. To say that the chemicals were pricey, would be a gross
> understatement. We bought them by the gallon, and each gallon cost an
> arm, a leg, and someone's first born son.
>
> The chemicals did the job for us because our usual need was to retrieve
> the failed components from the assembly. We had little concern for the
> assembly itself. The items we were after were in metal or ceramic
> packages, and therefore were not affected by the chemicals. Although the
> possibility of removing the epoxy and repairing an assembly exists, it
> is expensive and labor intensive, with a low probability of success.
>
> On the very rare occasion that a module had to be repaired because there
> was no other choice, a different technique was used. This technique is
> not generally available outside a lab like ours, but I present it just
> in case you have access to the necessary machinery/information.
>
> This technique requires good information on the construction of the
> module. We started by performing X-Ray in X, Y and Z axes. The X-Ray
> results were compared to the original assembly drawings, and the
> component of interest was located. By using extremely precise drilling
> and milling tools, combined with progressive X-Rays, a cavity was made
> around the part to be replaced. Every attempt was made to make the
> cavity very close to the part. The cavity was then filled with the
> chemical of choice, and the epoxy slowly scraped away, exposing the
> component. Just watching this process was painful. I don't even want to
> discuss how difficult it was to replace a component once the cavity was
> open and the defective component removed. To underscore: this was only
> done when there was no possibility of getting a replacement module, or
> the time it would take to get a replacement would have a devastating
> impact on delivery schedule.
>
> Harvey A
>
> On 7/3/2017 11:57 AM, 'Technotronic~Dimensions'
> infotech@... [Homebrew_PCBs] wrote:
>>
>> Hi
>>
>> Sorta new here and trying to catch on to some of the procedures described
>> here.
>>
>> Was wondering if anyone knows if theres a chemical or chemicals (s) that
>> will safely dissolve epoxy that some manufacturers
>> use to encapsulate boards to protect them and make them more or less
>> unservicable when a component fails?
>>
>> I have hears there is a chemical that they can be soaked in for many
>> days,
>> and you have to check on it daily before it eats through
>> things that u dont want it to damage.
>>
>> Steve Hearns
>> Technotronic Dimensions [USA]
>> WWW.TECHNOTRONIC-DIMENSIONS.COM
>> 1.518.663.3421 (MAIN)
>> 1-877-817-9885 (Voice / Fax Toll Free - US Only)
>> E-Mail: Steve@...
>> --
>> Webmaster, Parts-Link: (http://www.parts-link.com)
>> Group Moderator:
>> TV-Repair (http://groups.yahoo.com/group/tv-repair)
>> Monitor-Repair (http://groups.yahoo.com/group/monitor-repair)
>>
>> ----- Original Message -----
>> From: "LEON HELLER leon355@... [Homebrew_PCBs]"
>> <Homebrew_PCBs@yahoogroups.com>
>> To: <Homebrew_PCBs@yahoogroups.com>
>> Sent: Monday, July 03, 2017 12:56 AM
>> Subject: Re: [Homebrew_PCBs] Ferric chloride staining PCB substrate
>>
>> Oxalic acid removes ferric chloride stains. I've got a big bottle of it
>> somewhere but have never used it.
>> Leon
>>
>> On Monday, 3 July 2017, 2:56, "'Brad' unclefalter@...
>> [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com> wrote:
>>
>>
>
>