April 2014 • The PCB Magazine 25
LEAD-FREE REFLOW FOR HIGH-LAYER-COUNT PCBS continues
HDI substrates by adopting direct metalizaton
and new technologies in electroplating such
as copper super fill and periodic reverse copper
plating (PPR). These processess aid in building
reliability into the vias that lead-free assembly
requires.
PCB
References
1. Kelley, Edward, "Reengineering FR-4 Base
Materials for Improved Multilayer PCB Perfor-
mance," The Board Authority-Live, June 2004.
2. Chrisafides, Christos, "Different Curing
System Can Improve Laminate Performance,"
The Board Authority-Live, June 2004.
3. Holden, H., "How To Get Started In HDI
With Microvias," www.circuitree.com, Nov.
2003.
4. Holden, H., "Understanding the Through-
Hole Density Barrier," connection.ebscohost.
com, Feb. 2007.
5. Nadolny, Jim, "Advantages of BGA for
Backplane Connectors," DesignCon 2002-Tec-
Forum HP-TF4, pp.5.
6. Adolny, Jim, "Advantages of BGA for
Backplane Connectors," DesignCon 2002-Tec-
Forum HP-TF4, pp.17.
7. HDI Handbook, www.hdihandbook.
8. Carano, Michael, "Comparing the Reli-
ability of a Graphite-based Direct Metalization
Process to Conventional Electroless Copper for
Rigid Through-Hole Printed Circuit Boards,"
Electronic Circuits World Convention 12, No-
vember 2011, Taipei, Taiwan.
9. Carano, Michael, "Via filling Technol-
ogy," CircuiTree, 2007.
Figure 11: conversion of a 22-layer tH multilayer to a 14-layer Hdi (1+12+1) in order to reduce its
thickness from 0.127" to 0.063" to gain reliability in lF smt assembly.
Happy Holden is the retired direc-
tor of electronics technologies at
gentex corporation in Zeeland,
michigan. to contact Holden,
click here.
michael carano is with omg
electronic chemicals, a developer
and provider of processes and
materials for the electronics in-
dustry supply chain and regular
columnist for the pcB magazine.
to contact carano, click here.
