The Low Mass Solution to 0402 Tombstoning
Author: Eric Reno, product engineer II
Tombstoning occurs when a part is pulled up on one side, assuming a vertical orientation that looks like a graveyard headstone. Suntron performed a dimensional evaluation on seven manufacturers of capacitors and six manufacturers of resistors commonly used by its customers. The analysis, which looked at the component body and its terminations, revealed was that 86% of the capacitor manufacturers and 50% of the resistor manufacturers had different body and termination dimensions and tolerances. (By comparison, a similar evaluation of the same component manufacturers' 0201 and 0603 package types showed identical parts.)
Reno says these variations in the components must be accounted for in the pad geometry, or else tombstoning may occur. He also recommends treating each pad as a group, and ensuring the copper density of each pad is equal (or very close), meaning both pads achieve the same temperature and liquidus at the same time. Also, Reno says, both pads should achieve solder flow to exposed copper at the same time, and be equal in solder volume necessary to control capillary action.
Reno recommends a specific pad geometry for 0402a, reduces the soldermask clearance to 0.002" (from 0.005"), and suggests a connecting trace between pad and plane (or very wide trace) to be equal as the sister pad.
To view the white paper, click here.
By Matt Chanoff, Senior Consultant, Technology Forecasters Inc.
This white paper is an introduction to and spin-off from a larger, ongoing effort that Technology Forecasters Inc. (TFI) has undertaken to assess and benchmark the performance of outsource manufacturing companies, both electronics manufacturing services (EMS) and original design manufacturer (ODM), worldwide.
The purpose of this White Paper is to lay out a practical framework for identifying and understanding “best practices” as they relate to electronics outsource manufacturing, without attempting to assess the performance of any specific manufacturers.
This is a long-term, cumulative, project, and it is designed to benefit from multiple interviews undertaken over time, in order to discern changes and trends
in outsourcing practices. TFI is interviewing globally and including manufacturers of all sizes but is focusing solely on the original equipment manufacturer (OEM)
perspective: What, from the perspective of OEMs, are the best practices of their outsourcing partners? What are the best practices OEMs employ to maximize
the benefits of outsourcing? The value of this approach is that it allows OEMs that currently outsource to benchmark the performance and services of their
partners, their internal manufacturing, and their in-house outsource management against the performance and services obtained by their competitors and peers.
OEMs that do not currently outsource, or that may increase the scope of their outsourcing, can gain insight into services and the level of service available. EMS
and ODM companies can compare their offerings with those of competitors and can identify areas of improvement or investment.
How three small-to-medium-sized companies have achieved lasting success in this tough, dynamic industry.
EMS and ODM Vital Roles in Customers’ Sustainability Roadmaps: How to create competitive advantage and increase customer loyalty
Technology Forecasters Keynote Presentation on the 30-year migration of the supply chain from OEMs to Contract Manufacturers and its impact on the OEM’s sustainability plans at the May 2011 International Electronics Recycling Conference and Expo (IERCE) in Las Vegas, NV.
Clients, colleagues, and friends who have seen or of deplorable conditions of certain manual electronics “recycling” communities in disadvantaged regions of the world ask, “How do I know where the products I no longer need end up, and how they are processed? Am I really doing the right thing by recycling them?” They ask how to tell which electronics recycling services are responsible for human and environmental health, adding, “Wouldn’t it be a good idea if there were certifications or standards for recyclers so we could choose the ethical ones?”
As far as standards, many recyclers are getting ISO 14001 certified, which provides a structure for continuous management and reduction of environmental impacts but by itself doesn’t prescribe performance requirements or audits for electronics-recycling practices. Now, we can point to two standards for electronics recycling – R2 and e-Stewards – to compare and contrast and find recyclers becoming certified to the standard of their choice, or both.
This white paper explains how the "IEEE P1687 IJTAG" standard will enable instruments originally embedded into chips for chip characterization and test can be reused later in circuit board design validation, volume manufacturing test and field service troubleshooting. The white paper describes and illustrates the on-chip IJTAG architecture. The paper also describes how validation, test and debug engineers will be able to deploy IJTAG-based tools to automate and schedule the operations of embedded instrument.
To download the paper, click here.
FPGA devices create compelling business drivers generating a tidal wave of FPGA adoption for the implementation of system PCB designs. Obviously, the time to market advantages and capacity/performance characteristics of FPGA devices have delivered on the promise for a viable alternative to more capital resource intensive custom IC/ASIC solutions as well as a successful consolidation vehicle for standard “off the shelf” components in system design creation.