Electronics Manufacturing Technical Articles

Study of Various PCBA Surface Finishes

Nov 25, 2015 | Georgie Thein, David Geiger, and Murad Kurwa.

In this study various printed circuit board surface finishes were evaluated, including: organic solderability preservative (OSP), plasma finish (PF), immersion silver (IAg), electroless nickel / immersion silver (ENIS), electroless nickel / immersion gold hi-phosphorus (ENIG Hi-P), and electroless nickel / electroless palladium / immersion gold (ENEPIG). To verify the performance of PF as a post-treatment option, it was added to IAg, ENIG Hi-P, and ENEPIG to compare with non-treated. A total of nine groups of PCB were evaluated. Each group contains 30 boards, with the exception on ENIS where only 8 boards were available....

Publisher: Flex (Flextronics International)

HALT Testing of Backward Soldered BGAs on a Military Product

Nov 19, 2015 | B. Gumpert, B. Fox, L. Woody

The move to lead free (Pb-free) electronics by the commercial industry has resulted in an increasing number of ball grid array components (BGAs) which are only available with Pb-free solder balls. The reliability of these devices is not well established when assembled using a standard tin-lead (SnPb) solder paste and reflow profile, known as a backward compatible process. Previous studies in processing mixed alloy solder joints have demonstrated the importance of using a reflow temperature high enough to achieve complete mixing of the SnPb solder paste with the Pb-free solder ball. Research has indicated that complete mixing can occur below the melting point of the Pb-free alloy and is dependent on a number of factors including solder ball composition, solder ball to solder paste ratio, and peak reflow times and temperatures. Increasing the lead content in the system enables full mixing of the solder joint with a reduced peak reflow temperature, however, previous research is conflicting regarding the effect that lead percentage has on solder joint reliability in this mixed alloy solder joint....

Publisher: Lockheed Martin Corporation

The Perfect Copper Surface

Nov 12, 2015 | Eric Stafstrom; Technic Inc, Garo Chehirian; Tech-Etch.

In order to provide the functionality in today’s electronics, printed circuit boards are approaching the complexity of semiconductors. For flexible circuits with 1 mil lines and spaces, this means no nodules, no pits, and excellent ductility with thinner deposits. One of the areas that has to change to get to this plateau of technology is acid copper plating. Acid copper systems have changed in minor increments since their introduction decades ago. However, the basic cell design using soluble anodes in slabs or baskets has for the most part remained the same. Soluble, phosphorized, copper anodes introduce particulate and limits the ability to control plating distribution....

Publisher: Technic Inc.

Print Performance Studies Comparing Electroform and Laser-Cut Stencils

Nov 05, 2015 | Rachel Miller Short, William E. Coleman Ph.D.; Photo Stencil | Joseph Perault; Parmi.

There has been recent activity and interest in Laser-Cut Electroform blank foils as an alternative to normal Electroform stencils. The present study will investigate and compare the print performance in terms of % paste transfer as well the dispersion in paste transfer volume for a variety of Electroform and Laser-Cut stencils with and without post processing treatments. Side wall quality will also be investigated in detail. A Jabil solder paste qualification test board will be used as the PCB test vehicle....

Publisher: Photo Stencil LLC

Novel Approaches for Minimizing Pad Cratering

Oct 29, 2015 | Chen Xu, Yunhu Lin; Alcatel-Lucent, Yuan Zeng, Pericles A. Kondos; Unovis-Solutions.

With the electronic industry moving towards lead-free assembly, traditional SnPb-compatible laminates need to be replaced with lead-free compatible laminates that can withstand the higher reflow temperature required by lead-free solders. Lead-free compatible laminates with improved heat resistance have been developed to meet this challenge but they are typically more brittle than SnPb laminates causing some to be more susceptible to pad cratering. In this paper, two novel approaches for minimizing pad cratering will be discussed. Preliminary results which validate the two approaches will also be presented....

Publisher: Alcatel-Lucent

Tin Whisker Risk Management by Conformal Coating

Oct 22, 2015 | Linda Woody, William Fox; Lockheed Martin Missiles and Fire Control

The objective of this study is to evaluate conformal coatings for mitigation of tin whisker growth. The conformal coatings chosen for the experiment are acrylic, polyurethane and parylene. Also included in this paper are tin whisker inspection results of tin-plated braiding and wire that was exposed to an environment of 50°C with 50% relative humidity for over five years....

Publisher: Lockheed Martin Corporation

Optimizing the Insulated Metal Substrate Application with Proper Material Selection and Circuit Fabrication

Oct 15, 2015 | Dave Sommervold, Chris Parker, Steve Taylor, Garry Wexler

The ever expanding growth in the use of insulated metal substrates (IMS) in power electronics requires a focus on material and mechanical configuration for each application. By optimizing the material makeup and printed board format, performance and reliability expectations can be further achieved. The thermal performance and electrical isolation needs are driven by the power requirements, but considerations of temperature range, mechanical durability and format, along with the physical package surrounding the substrate must also be managed. With a variety of material configurations and circuit format capabilities, the choices become a balancing of options to maximize performance and minimizing cost through Design For Manufacturability (DFM) in the circuit board fabrication. These challenges present the IMS printed board fabricator with material selections and fabrication processes unlike those for other printed board or ceramic applications....

Publisher: The Bergquist Company

Preparing for Increased Electrostatic Discharge Device Sensitivity

Oct 08, 2015 | Julian A. Montoya, Intel Corporation Hillsboro, Oregon

With the push for ever improving performance on semiconductor component I/O interfaces, semiconductor components are being driven into a realm which makes them more sensitive to electrostatic discharge, potentially increasing in sensitivity by 50% every 3-5 years. Today, the majority of modern day semiconductor components are being designed to meet 250Volts of charge device model sensitivity, and that could decrease to 125Volts in the next 3-5 years, and could again decrease to 50Volts-70Volts in the following 3-5 years. The entire electronics industry must prepare for this challenge....

Publisher: Intel Corporation

Printing of Solder Paste - A Quality Assurance Methodology

Oct 01, 2015 | Lars Bruno and Tord Johnson Ericsson AB and MTEK Consulting AB

Solder paste printing is known to be one of the most difficult processes to quality assure in electronic manufacturing. The challenge increases as the technology development moves toward a mix between large modules and small chip components on large and densely populated printed circuit boards. Having a process for quality assurance of the solder paste print is fast becoming a necessity.

This article describes a method to ensure quality secured data from both solder paste printers and inspection machines in electronic assembly manufacturing. This information should be used as feedback in order to improve the solder paste printing process....

Publisher: Ericsson AB

Gold Stud Bump Flip Chip Bonding on Molded Interconnect Devices

Sep 23, 2015 | Dick Pang, Weifeng Liu, Anwar Mohammed, Elissa Mckay, Teresita Villavert and Murad Kurwa

A molded interconnect device (MID) is an injection molded thermoplastic substrate which incorporates a conductive circuit pattern and integrates both mechanical and electrical functions. (...) Flip chip bonding of bare die on MID can be employed to fully utilize MID’s advantage in device miniaturization. Compared to the traditional soldering process, thermo-compression bonding with gold stud bumps provides a clear advantage in its fine pitch capability. However, challenges also exist. Few studies have been made on thermocompression bonding on MID substrate, accordingly little information is available on process optimization, material compatibility and bonding reliability. Unlike solder reflow, there is no solder involved and no “self-alignment,” therefore the thermo-compression bonding process is significantly more dependent on the capability of the machine for chip assembly alignment....

Publisher: Flex (Flextronics International)