Driving Innovation: Direct Imaging vs. Conventional Exposure
It’s Only Common Sense: Selling to Today's Generation of Buyers
Dan’s Biz Bookshelf: ‘Believe in Better'
Lead-free Reflow for High-layer-count PCBs
June 17, 2014 | Happy Holden, Retired, and Michael Carano, OMG Electronic Chemicals, LLCEstimated reading time: 1 minute
This article is an update of the Holden-Carano article originally published in the February 2013 issue of The PCB Magazine.
Abstract
One of the most difficult printed circuit boards to adapt to Pb-free assembly processes is the high-layer count multilayer. Often, these multilayers have through-hole and hand-soldered components, and requirements for two or more rework cycles. The higher reflow temperatures and slower wetting of lead-free solders place an enormous strain on the laminate and copper-plated hole barrel. In many cases, the boards cannot be assembled reliably even with newer, higher thermal performance FR-4s.
One solution to this problem is to redesign the multilayer using current design rules and newer innovative fabrication technologies. This article will review four of these new and enabling technologies:
- Laser-drilled microvias;
- Routing BGA using channels;
- Contribution of new SMT connectors; and
- Layer assignment changes (architectures).
Microvias offer the most significant opportunity to reduce not only the layers and thicknesses of multilayers, but also their cost while improving their electrical performance and density. Several examples will illustrate these new opportunities. Since blind vias are surface phenomena, to get the maximum benefit from them, layer assignment for signal, ground and power need to be reviewed and alternative constructions considered. These blind vias, by reducing the number of through-holes, contribute to increase routing density that allows the lower layer usage. Finally, by replacing through-hole connectors with surface mount connectors, higher connector density and improved electrical performance can be realized.
The resulting new multilayers are not only thinner, cheaper, and easier to design, but are less costly and suitable for lead-free assembly.
Read the full article here.
Editor's Note: This article originally appeared in the April 2014 issue of The PCB Magazine.
Share on:
Suggested Items
The Evolution of Picosecond Laser Drilling
06/19/2025 | Marcy LaRont, PCB007 MagazineIs it hard to imagine a single laser pulse reduced not only from nanoseconds to picoseconds in its pulse duration, but even to femtoseconds? Well, buckle up because it seems we are there. In this interview, Dr. Stefan Rung, technical director of laser machines at Schmoll Maschinen GmbH, traces the technology trajectory of the laser drill from the CO2 laser to cutting-edge picosecond and hybrid laser drilling systems, highlighting the benefits and limitations of each method, and demonstrating how laser innovations are shaping the future of PCB fabrication.
Day 2: More Cutting-edge Insights at the EIPC Summer Conference
06/18/2025 | Pete Starkey, I-Connect007The European Institute for the PCB Community (EIPC) summer conference took place this year in Edinburgh, Scotland, June 3-4. This is the third of three articles on the conference. The other two cover Day 1’s sessions and the opening keynote speech. Below is a recap of the second day’s sessions.
Day 1: Cutting Edge Insights at the EIPC Summer Conference
06/17/2025 | Pete Starkey, I-Connect007The European Institute for the PCB Community (EIPC) Summer Conference took place this year in Edinburgh, Scotland, June 3-4. This is the second of three articles on the conference. The other two cover the keynote speeches and Day 2 of the technical conference. Below is a recap of the first day’s sessions.
Preventing Surface Prep Defects and Ensuring Reliability
06/10/2025 | Marcy LaRont, PCB007 MagazineIn printed circuit board (PCB) fabrication, surface preparation is a critical process that ensures strong adhesion, reliable plating, and long-term product performance. Without proper surface treatment, manufacturers may encounter defects such as delamination, poor solder mask adhesion, and plating failures. This article examines key surface preparation techniques, common defects resulting from improper processes, and real-world case studies that illustrate best practices.
RF PCB Design Tips and Tricks
05/08/2025 | Cherie Litson, EPTAC MIT CID/CID+There are many great books, videos, and information online about designing PCBs for RF circuits. A few of my favorite RF sources are Hans Rosenberg, Stephen Chavez, and Rick Hartley, but there are many more. These PCB design engineers have a very good perspective on what it takes to take an RF design from schematic concept to PCB layout.