<< >Does anyone have specification for rinse water quality in a black oxide
>line? We are trying to determine and establish quality levels for our
>rinses in the horizontal black oxide line. We would also like to establish
>cause and effect defects of poor rinsing. Your help would be greatly
>appreciated
>
>
You have asked a very interesting question, for which I suspect there may be
few answers. I take this opportunity to repond, but not actually answer the
specific question, because it brings up one of the more persistent myths in
the industry.
The reality is that virtually no one, to my knowlege, has specifications on
their rinse water after black oxide, and in fact, due to the myth I am going
to discuss, the actual quality of most rinsing after black oxide is pretty
terrible.
The myth I allude to is the belief that alkaline solutions rinse more poorly
than neutral or acid solutions. This myth is undoubtedly generated by the
apparent difficulty of rinsing alkali solutions from your hands, they stay
slippery for a long time, yet, treating them with an acid causes this to go
away immediately. Therefore alkali rinses poorly?
No not so...
Turns out that when alkaline solutions hit your hands, they convert the fixed
oils on the skin to soaps, and you never actually rinse that stuff away. (It
has to wear off). What actually happens is that you convert it to hard
water soap scum, or if you hit with acid, to fatty acid, and in either case
it ceases being slippery.
So in fact alkali rinses just as easily as acid, from metal.
However, many, (most) pcb shops in the US use a hot final rinse in the oxide
line, to "speed" rinsing. Normally, because they do not want to support the
local power company, this final (hot) rinse gets VERY little turn over, and
because it is hot, and evaporation is occuring, which concentrates the salts
in solution, the quality of this final rinse water tends to be pretty bad.
This is made worse by the fact that the panels leave this final rinse tank
hot, and any remaining water, containing residuals, tends to evaporate,
rather than drain off the surface. Of course the evaporation drops any
residuals on the surface, rather than the drainage carrying them away.
A story from my history relating to this matter:
I had an interesting experience installing our oxide chemistry at a major pcb
manufacturer, and made a critical sales tactical error, and convinced the
general manager of the shop that our chemistry was the key to improving his
life, but neglected to talk to the Director of Engineering about it. The
General Manager told the Director of Engineering to install our chemistry,
and the Director of Engineering was not real thrilled to be told which
chemistry to use. However, he did it, but in the process, wanted us to fail,
and told us to specify the process, with no consideration of what was
currently being done, hoping that we would spec out a process destined to
fail, based on the fact that we did not have full knowlege of the
peculiarities of the line.
In the process of specifying the process, we specified cascade deionized
water rinses, with no final hot rinse. The Director of Engineering was
shocked, as was his engineers that we did not want a hot final rinse. To
their amazement, the processs went on to work quite well, and the quality of
the oxide improved markedly (uniformity and peel strengths), this in spite of
the fact that they had been using an oxide from a famous, even legendary,
supplier.
The droll part of this is, that their analysis of the results was that it was
the uniqueness of this oxide chemistry that caused them to not require a hot
final rinse, not that it may have been a misunderstanding of the process.
And you carry on...
Rudy Sedlak
RD Chemical Company
[log in to unmask] >>
---------------------
Forwarded message:
Subj: Fwd: Fab: Rinse water quality
Date: 97-06-18 12:43:25 EDT
From: RSedlak
To: RSedlak
---------------------
Forwarded message:
Subj: Re: Fab: Rinse water quality
Date: 97-06-18 12:41:00 EDT
From: RSedlak
To: [log in to unmask]
CC: [log in to unmask]
In a message dated 97-06-15 11:54:09 EDT, you write:
>Does anyone have specification for rinse water quality in a black oxide
>line? We are trying to determine and establish quality levels for our
>rinses in the horizontal black oxide line. We would also like to establish
>cause and effect defects of poor rinsing. Your help would be greatly
>appreciated
>
>
You have asked a very interesting question, for which I suspect there may be
few answers. I take this opportunity to repond, but not actually answer the
specific question, because it brings up one of the more persistent myths in
the industry.
The reality is that virtually no one, to my knowlege, has specifications on
their rinse water after black oxide, and in fact, due to the myth I am going
to discuss, the actual quality of most rinsing after black oxide is pretty
terrible.
The myth I allude to is the belief that alkaline solutions rinse more poorly
than neutral or acid solutions. This myth is undoubtedly generated by the
apparent difficulty of rinsing alkali solutions from your hands, they stay
slippery for a long time, yet, treating them with an acid causes this to go
away immediately. Therefore alkali rinses poorly?
No not so...
Turns out that when alkaline solutions hit your hands, they convert the fixed
oils on the skin to soaps, and you never actually rinse that stuff away. (It
has to wear off). What actually happens is that you convert it to hard
water soap scum, or if you hit with acid, to fatty acid, and in either case
it ceases being slippery.
So in fact alkali rinses just as easily as acid, from metal.
However, many, (most) pcb shops in the US use a hot final rinse in the oxide
line, to "speed" rinsing. Normally, because they do not want to support the
local power company, this final (hot) rinse gets VERY little turn over, and
because it is hot, and evaporation is occuring, which concentrates the salts
in solution, the quality of this final rinse water tends to be pretty bad.
This is made worse by the fact that the panels leave this final rinse tank
hot, and any remaining water, containing residuals, tends to evaporate,
rather than drain off the surface. Of course the evaporation drops any
residuals on the surface, rather than the drainage carrying them away.
A story from my history relating to this matter:
I had an interesting experience installing our oxide chemistry at a major pcb
manufacturer, and made a critical sales tactical error, and convinced the
general manager of the shop that our chemistry was the key to improving his
life, but neglected to talk to the Director of Engineering about it. The
General Manager told the Director of Engineering to install our chemistry,
and the Director of Engineering was not real thrilled to be told which
chemistry to use. However, he did it, but in the process, wanted us to fail,
and told us to specify the process, with no consideration of what was
currently being done, hoping that we would spec out a process destined to
fail, based on the fact that we did not have full knowlege of the
peculiarities of the line.
In the process of specifying the process, we specified cascade deionized
water rinses, with no final hot rinse. The Director of Engineering was
shocked, as was his engineers that we did not want a hot final rinse. To
their amazement, the processs went on to work quite well, and the quality of
the oxide improved markedly (uniformity and peel strengths), this in spite of
the fact that they had been using an oxide from a famous, even legendary,
supplier.
The droll part of this is, that their analysis of the results was that it was
the uniqueness of this oxide chemistry that caused them to not require a hot
final rinse, not that it may have been a misunderstanding of the process.
And you carry on...
Rudy Sedlak
RD Chemical Company
[log in to unmask]
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