Technical Articles From Cookson Electronics

Effect Of Silver In Common Lead-Free Alloys

Sep 08, 2021 | Ranjit Pandher, Tom Lawlor

There is need in the industry to understand the effects of silver presence in solders from various applications perspective. This article will attempt to present a review of the key published results on the silver containing alloys along with results of our internal studies on wave soldering, surface mount and BGA/CSP applications. Advantages and disadvantages of silver at different levels will be discussed. Specifically this report will focus on the effect of silver on process conditions, drop shock resistance, solder joint survivability in high strain rate situations, thermal fatigue resistance, Cu dissolution and effects of silver in combination with other alloy additives. Specific application problems demanding high silver level and other requiring silver level to the minimum will be discussed....

A PROCEDURE TO DETERMINE HEAD-IN-PILLOW DEFECT AND ANALYSIS OF CONTRIBUTING FACTORS

Jul 02, 2020 | Ranjit Pandher, Rahul Raut, Michael Liberatore, Navendra Jodhan, and Karen Tellefsen

Head-in-Pillow (HIP) defects are a growing concern in the electronics industry. These defects are usually believed to be the result of several factors, individually or in combination. Some of the major contributing factors include: surface quality of the BGA spheres, activity of the paste flux, improper placement / misalignment of the components, a non-optimal reflow profile, and warpage of the components. To understand the role of each of these factors in producing head-in-pillow defects and to find ways to mitigate them, we have developed two in-house tests....

SMT Troubleshooting Guide

Oct 20, 2018 | Cookson Electronics

With this easy-to-use Troubleshooting Guide, you can learn to troubleshoot common SMT issues. After using it a few times, it will become an essential companion for you and anyone in your company responsible for operating an SMT line.

This Guide offers troubleshooting advice for common SMT assembly issues by process defect. If your issue is not resolved after following the steps to help identify the possible root cause and solution, please contact your Cookson Electronics representative who will be able to provide you with further assistance....

Stencil Design for Lead-Free SMT Assembly

Mar 05, 2018 | Chrys Shea

In order to comply with RoHS and WEEE directives, many circuit assemblers are transitioning some or all of their soldering processes from tin-lead to lead-free within the upcoming year. There are no drop-in replacement alloys for tin-lead solder, which is driving a fundamental technology change. This change is forcing manufacturers to take a closer look at everything associated with the assembly process: board and component materials, logistics and materials management, solder alloys and processing chemistries, and even soldering methods.

Do not expect a dramatic change in soldering behavior when moving to lead-free solders. The melting points of the alloys are higher, but at molten temperatures the different alloys show similar behaviors in a number of respects. Expect subtler changes, especially near the edges of a process window that is assumed based on tin-lead experience rather than defined through lead-free experimentation. These small changes, many of them yet to be identified and understood, will manifest themselves with lower assembly yields. The key to keeping yields up during the transition to lead-free is quickly learning what and where the subtle distinctions are, and tuning the process to accommodate them....

PCB Surface Finishes & Cost Effective Pb Free Assembly Materials

Mar 27, 2014 | Richard Puthota Director – Business Development & CTS India & Africa, Cookson Electronics

The surface finish you select will have a large influence on quality, reliability and cost. It is a complex decision that impacts many areas of the business. Select a finish that optimal for the business (and not just one function). Know that there are engineering tricks to improve on weak areas of each finish. Stay current in this field because new developments continue to be made....

Conductive Adhesives: TheWay Forward

Nov 04, 2010 | Dr. Ken Gilleo

Conductive Adhesives represent an intrinsically clean, simple and logical solution for a myriad of electrical interconnect challenges. Adhesives not only provide a "lead-free", "no clean" alternative to solder, these highly compatible materials offer viab...

Drop Shock Reliability of Lead-Free Alloys - Effect of Micro-Additives

Jun 11, 2009 | Ranjit S Pandher, Brian G Lewis, Raghasudha Vangaveti, Bawa Singh

The shock reliability of solder joints has become a major issue for the electronic industry partly because of the ever increasing popularity of portable electronics and partly due the transition to lead free solders....

Selection Of Wave Soldering Fluxes For Lead-Free Assembly

Jul 10, 2008 | Chrys Shea, Sanju Arora, Steve Brown

This paper reviews the J-STD-004 and how it is used in flux categorization and selection. It also discusses the major types of flux formulations available, and the design, process and reliability implications of using each type. The purpose of the paper is to help the reader make an informed choice when selecting wave solder fluxes for lead-free processing....

Tutorial: How to Select the Best Stencil for SMT and Advanced IC Package Printing

May 05, 2003 | By Alden Johnson, Cookson Electronics Equipment, Franklin,Mass.

The stencil selection process can be confusing, particularly when creating a stencil for a new application. This tutorial, which covers stencils for SMT and advanced IC packaging applications, offers guidelines to assist users in stencil selection and print optimization....

Equipment Impacts of Lead Free Wave Soldering

Apr 18, 2003 | Jim Morris, Advanced Development Manager, Cookson Electronics Equipment & Matthew J. O'Keefe, Ph.D., Associate Professor of Metallurgical Engineering, University of Missouri

The popular tin (Sn) rich lead free solders are causing severe corrosion to many of the materials used in today's Wave Solder systems. Users are experiencing higher maintenance frequency and reduced life of wave solder machine components. This paper describes the effects of Sn rich solders in contact with various materials and discusses alternate methods to alleviate this problem....