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.


On 7/3/2017 10:32 PM, 'Technotronic~Dimensions' 
infotech@... [Homebrew_PCBs] wrote:
>
> 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@...
> --
> 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: "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:
> >>
> >>
> >
> >
>
>