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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