Brian,
What a good bit of historical background on EDCF! 'Younger generation'
is only interested in modern technologies and their application. How
many actually have interest in the "great great grand parents " of these
modern technologies.
It is a treasure to have people like you around. There is a saying in
Chinese that goes something like this : "A family that have an old
member, is a family that have a treasure!"
Regards,
Wee Mei
Brian Ellis wrote:
> OK, No one seems to have the answer.
>
> It was the Royal Mint in London, strangely enough. In the good old days
> when there were 12 pennies to the shilling and 20 shillings to the
> pound, the farthing, ha'penny and penny pieces were made of a special
> four-component bronze alloy, which was precisely controlled. This was
> cast into small ingots and then rolled into strips about 100 mm wide
> (from memory) and the blanks stamped out. It was found that re-melting
> the perforated strips led to variations in the alloy and a lot of work
> to correct it. In the 1930s, it was decided to try to purify the metals
> and the copper was recovered electrolytically. This was a fairly
> high-current process with polished stainless steel cathodes. It was
> actually plated to several mm thickness before being stripped and then
> chopped into pieces for the furnace.
>
> Someone (I think in Formica Limited, North Shields, England) remembered
> this process when rolled copper laminate suffered from bond strength
> problems and he asked the Royal Mint to provide a few sheets where the
> process was stopped after a few minutes. As they were smooth on one side
> and rough on t'other, the bond strength proved much better. Thus was
> EDCF born for printed circuitry.
>
> Brian
>
> Brian Ellis wrote:
>
>> T&T nor MIT certainly weren't the first to make EDCF. I'm not sure of
>> the exact date, but I believe it was done in the 1930s, obviously
>> nothing to do with printed circuits. However, it was a batch process on
>> large polished stainless steel sheets, not a continuous drum cathode,
>> which was developed in the early 1950s to meet the demand for a more
>> rational process. If I remember correctly, the sheets were 3 x 4 feet,
>> but about 6" all round was scrapped as only the centre part was of
>> uniform thickness. The rough (very!) side of the copper was sprayed with
>> an adhesive. The laminate made from it was made by the Formica company
>> on a phenolic paper substrate (later designated as XP, nothing to do
>> with Microsoft, as Bill Gates wasn't even born then!). The adhesion was
>> considerably better than with the brushed rolled copper tried before,
>> but I think the T&T advance was that, with their continuous process,
>> they were able to treat the copper by chemically oxidising it. Gould
>> later improved on the treating by depositing a thin layer of zinc, which
>> formed a brass by diffusion during the press cycle, providing a better
>> bond to the epoxy.
>>
>> I'll let you have another try.
>>
>> Brian
>>
>> PS Sorry for having hi-jacked the thread by going off-topic.
>> Mary Jane Chism wrote:
>>
>>> Group,
>>>
>>> Is it mentioned anywhere in any of the IPC standards a visual acuity
>>> for
>>> solder inspection? Thanks.
>>>
>>> Mary Jane Chism
>>>
>>>
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