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Date: | Fri, 22 Jul 2005 16:00:27 -0400 |
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Internal thieving is an important factor the PCB panel design. This
serves to provide a uniform flow restriction to the bonding materials as
it is processed in the lamination cycle under heat and pressure. The
base materials are inherently instable and will be influenced in
movement during lamination in relation to the resin flow conditions.
This reduces positional differences that result from core to core and
panel to panel. The placement of thief also provides a uniform pressure
throughout the stack of panels in the lamination book being processed,
which also has affects related to stability and bonding conditions of
materials in the package.
External thief, thus it name, is to normalize the current densities
across the panel being plated. Constant ASF produces high and low
current densities which cause gradients in plating thickness and also
deposit characteristics due to brightener variations at the plating
site.
The PCB house is at liberty to add out-board thief were needed to
balance the process conditions for a given design. The designers should
also develop a criteria to grant the variation to the PCB house to add
in-board thief where needed to further optimize the process. Many
designers direct the minimum spacing required for the addition and many
times "keep out areas" that are sensitive to additional basis metal.
This provides needed latitude in many cases to improve the fabrication
conditions of a design.
Jeffrey Bush
Director, Quality Assurance and Technical Support
VERMONT CIRCUITS INCORPORATED
76 Technology Drive - POB 1890
Brattleboro, Vermont 05302
Voice: 802.257.4571.21 Fax: 802.257.0011
http://www.vtcircuits.com
-----Original Message-----
From: Phil Nutting [mailto:[log in to unmask]]
Sent: Friday, July 22, 2005 2:35 PM
To: [log in to unmask]
Subject: [TN] layman's definition of theiving
Ok, I have to admit my lack of knowledge.
Can someone point me to a the Cliff's Notes version of Theiving on PC
boards?
Thanks in advance.
Phil
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Technet Mail List provided as a service by IPC using LISTSERV 1.8e
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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 847-615-7100 ext.2815
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