In a message dated 10/31/98 10:31:56, you wrote:
>Dear Sir :
>I work inn a high frequency PCB manufacturing company and I have the
>following questionns :
>1/ Why is it for copper plating (acid copper plating) the lower the
>   current, the more the throwing power ? If I start to plate copper
>   on the PTH walls with high current density after PTH, what will
>   happen ?
>2/ Our customer always specify to have a certainn thickness innside the
>   PTH walls for copper. Why is that so for high frequency PCB ?
>   What happen if copper thickness is thinner than the specified
>   thickness at high frequencies ?
>Thanks for your help !!!!!!!

Hi Francis,
Your questions do not really have anything to do with high frequency
applications specifically, but are for any PCB.
1/ If you plate PTHs/PTVs with high average plating currents, you will get
much thicker plating near the PCB surfaces and thinner plating in the
middle;this is called dog-boning. In addition, the copper deposited will have
both low strength and low ductility. The consequence is, that in the location
of the PTV where the copper barrel experiences the highest stresses during
soldering processes, you have the thinnest copper (smallest load-bearing area
as well as stress concentration) and lousy copper quality to boot.
2/ The thinner the barrel copper thickness, and the higher the PTH aspect
ratio, the more likely you get fractured PTV barrels during soldering
processes.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask]

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