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Date: | Fri, 19 May 2006 07:32:10 EDT |
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In a message dated 5/19/2006 7:22:46 AM Eastern Daylight Time,
[log in to unmask] writes:
yes . I am talking about copper in the through hole only.
Suganthi
After drilling the hole in the board, you need to establish conductivity on
the dielectric for it to plate. Traditionally, this was done by using a
series of chemical steps, leading to deposit of 1.0 to 2.5 microns of electroless
copper. The chemical reaction is between formaldehyde and sodium hydroxide,
which donates the "electrons" to reduce copper sulfate in the electroless
bath to copper metal. This copper is not more than 10% of the total copper you
need in the hole
Once the conductivity is established, the board is placed in an
electroplating rack with contacts for DC electrical current. A rectifier converts AC
current into DC current. The board is the cathode, and copper metal is the
anode. The DC current causes copper to be reduced onto all conductive metal
surfaces exposed (the copper foil of the laminate and the now conductive
electroless copper in the holes). The anodes dissolve, keeping the copper balanced in
solution. Total thickness plated in the holes is historically 25 microns,
or more.
Denny Fritz
MacDermid.
On,
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