TECHNET Archives

June 2004

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Brian Ellis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 2 Jun 2004 10:03:43 +0300
Content-Type:
text/plain
Parts/Attachments:
text/plain (103 lines)
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
>>
>>
>> ---------------------------------------------------
>> Technet Mail List provided as a service by IPC using LISTSERV 1.8e
>> To unsubscribe, send a message to [log in to unmask] with following text in
>> the BODY (NOT the subject field): SIGNOFF Technet
>> To temporarily halt or (re-start) delivery of Technet send e-mail to
>> [log in to unmask]: SET Technet NOMAIL or (MAIL)
>> To receive ONE mailing per day of all the posts: send e-mail to
>> [log in to unmask]: SET Technet Digest
>> Search the archives of previous posts at:
>> http://listserv.ipc.org/archives
>> Please visit IPC web site
>> http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional
>> information, or contact Keach Sasamori at [log in to unmask] or
>> 847-509-9700 ext.5315
>> -----------------------------------------------------
>>
>>
>
> ---------------------------------------------------
> Technet Mail List provided as a service by IPC using LISTSERV 1.8e
> To unsubscribe, send a message to [log in to unmask] with following text in
> the BODY (NOT the subject field): SIGNOFF Technet
> To temporarily halt or (re-start) delivery of Technet send e-mail to
> [log in to unmask]: SET Technet NOMAIL or (MAIL)
> To receive ONE mailing per day of all the posts: send e-mail to
> [log in to unmask]: SET Technet Digest
> Search the archives of previous posts at: http://listserv.ipc.org/archives
> Please visit IPC web site
> http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional
> information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
> ext.5315
> -----------------------------------------------------
>
>

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------

ATOM RSS1 RSS2