All About Flex: Flexible Circuit Failure Analysis

Design reviews and early involvement by a circuit board fabrication house can minimize the possibility of field problems, but despite best efforts, there remain occasions when diagnosis of a poorly performing design is required. These instances occur most frequently in applications with unique performance requirements (mechanical abrasion, unique bending, and chemical environments are examples) and interactions among multiple features and requirements can make determination of cause and corrective action a complex analysis. Violations of standard design practice also can cause infant or long-term field failure. Solving a technical problem with a failed flexible circuit cable often requires sophisticated engineering diagnostic tools and analysis.

Failure analysis as an engineering service for flexible circuits is available from a variety of independent labs. Conclusions are formalized in written reports with engineering analysis, high magnification photography and design recommendations.

Diagnosing a premature failure of a flexible circuit can be elusive. The best analysis requires a combination of flexible circuit product expertise, sophisticated laboratory analysis technology, and formal problem-solving methodology.

The goal of most diagnostic endeavors is to:

  • Identify and isolate the problem
  • Identify the root cause
  • Recommend the appropriate changes to address the issue

An initial analytical step is to gather as much background information as possible. An excellent tool for organizing the background information in a systematic way is the Is/Is Not table. The table asks a series of questions to help the diagnostic team gather information in a logical and systematic method while helping focus the team on higher probability causation. The questions ask Who, What, Why, When, and How, as related to the problem. Problem statements are recorded along with eliminating possible options.

Below is an example of an IS/IS NOT table:

ISISNOT.jpg

Gathering the background information can be routine and in most cases examination of multiple parts under magnification is required. Sophisticated statistical analysis using factorial designed experiments might also be utilized and could take several days. Going through this process helps focus the diagnostic effort on the most likely causes based on the available empirical data.

The next diagnostic phase usually involves testing/analysis on the physical part. In most cases this requires destructive testing. The following are examples of analytical equipment frequently used for diagnosis:

  • Cross-sectional analysis
  • High-level magnification
  • High-voltage electrical tester
  • Time domain reflectometer
  • Frequency/spectrum analyzer
  • XRF (X-ray fluorescence)
  • X-ray
  • Infrared heat mapping

Once the failure has been physically identified, the root cause assessment can be performed. Additional analytical tools such as the Ishikawa or herringbone diagram might provide additional insight.

Documentation of the analysis performed and conclusions reached should be summarized through creation of a comprehensive report including photography, analytical tools employed, and organization of the data generated. In most cases a cause/corrective action linkage can be established with recommendations for next steps.  

Dave Becker is vice president of sales and marketing at All Flex Flexible Circuits LLC.

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2017

All About Flex: Flexible Circuit Failure Analysis

10-19-2017

Design reviews and early involvement by a circuit board fabrication house can minimize the possibility of field problems, but despite best efforts, there remain occasions when diagnosis of a poorly performing design is required.

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All About Flex: Flexible Circuits for Reusable Medical Products

09-21-2017

Flexible circuits have been used in medical devices and medical instrumentation for several decades. Flex circuits and flexible heaters can be ideal solutions in applications requiring lightweight, continuous movement, and highly reliable interconnections that are biocompatible.

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All About Flex: Flexible Circuits and Man-Made Satellites

09-12-2017

The first satellite was launched by the USSR in 1957. The U.S. successfully launched its first satellite, Explorer 1, in 1958 while announcing the intention to “win” the race to outer space. Today satellites serve many vital purposes.

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All About Flex: Using ZIF Connectors with Flexible Circuits

09-07-2017

Zero insertion force (ZIF) connectors are probably the most popular flexible circuitry connector because they allow the circuit to be inserted and removed multiple times with very little mechanical wear on the copper traces.

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All About Flex: The Anatomy of a Flex Circuit Cutline

08-22-2017

Numerous methods are used to create the cutline of a flexible circuit. With the various tooling options, the methods, process steps, tooling and technology are different. These differences affect the actual physics of cutting, and create slight variations on the circuit material.

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All About Flex: ITAR Registration

08-15-2017

Vendors building product for the defense industry often stipulate a supplier needs to be ITAR registered. ITAR stands for International Traffic in Arms Regulations and is a program run by the U.S. government to control the export of defense-related technology to foreign countries.

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Successful Flex Circuit Assembly

08-02-2017

Many contract manufacturers are reluctant to mix rigid and flexible circuits on the same assembly line as the handling and fixturing requirements can be quite different. Characteristics allowing a flexible circuit to be flexible can often present learning curve challenges when component or mechanical assembly is required. This article details some of the common issues experienced when assembling flexible circuits, and strategies to ensure reliable assembly.

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All About Flex: Button Plating on a Flexible Circuit

07-20-2017

Button plating describes a fabrication process widely used in the flex circuit industry to selectively electroplate copper to the vias and onto the pads capturing the vias. The rest of the copper traces do not have plating. Another industry term used to describe this feature is pads only plating. Producing a circuit with this processing methodology requires two photolithography steps.

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All About Flex: Trends in the Medical Electronics Industry

07-17-2017

The U.S. medical electronics industry has been one of the fastest growing industries over the past decade. Similarly, to the rest of the electronics world, growth has been accompanied by the adoption of significant new product technology and innovation.

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All About Flex: CAD for Flexible Circuits

07-12-2017

CAD engineers take a CAD file that defines a single part and panelize the data by creating a nested pattern repeated across the panel. Reverse nesting and off-angle part placement may optimize material utilization, which is a constant cost concern. But this optimization needs to be balanced by ease of stiffener placement and component assembly.

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2016

All About Flex: Customer Acquisition

12-22-2016

The “Customer Acquisition” process can be thought of as consisting of three major segments: collection, selection and execution. While these sub-divisions should be considered as intimately interrelated, examining them as separate disciplines can be enlightening.

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All About Flex: Disruption in the Supply Chain

12-08-2016

Manufacturers need a highly dependable supply chain to successfully support their products. This is especially true of custom designed and built components, as many times, only one supplier is available for a component since tooling and development costs discourage dual sourcing.

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All About Flex: Packaging Flexible Circuits and Assemblies

12-01-2016

Many facets are involved in delivering a flexible circuit. During the quote and design phase, requirements are reviewed. So assuming the relevant product documentation was gathered, the salesperson turned around the quote, and the customer placed an order and parts were built, it’s all over, right? Not quite. One critical aspect that does not get much discussion is packaging and shipping.

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All About Flex: Non-Copper Flexible Circuit Applications

11-22-2016

While pure copper is the most common choice for flexible circuit fabrication, there are times a different metal is more suitable for an application. Copper is well known for its excellent electrical and thermal conductivity, but there are applications where the best thermal or electrical conductivity can be a disadvantage.

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All About Flex: Flex Circuit Specifications for Commercial and Military Applications

10-27-2016

Applications across the various markets for printed circuit boards can have significantly different specifications and performance requirements. Circuits for toys and games logically have lower performance requirements than those used in medical devices. IPC-6013 is an industry-driven specification that defines the performance requirements and acceptance features for flexible printed circuit boards.

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All About Flex: Five Characteristics of a Reliable Flexible Circuit Supplier

10-27-2016

Due diligence when selecting a source for a custom electronic product can be a critical sourcing procedure. Chains are only as good as the weakest link, and the electronic components assembled to create a marketable product need to combine into a robust solution.

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All About Flex: Flexible Circuit Prototypes

10-13-2016

Most electronic projects begin with at least one build of prototype parts before moving into volume manufacturing. But the definition of a flex circuit prototype can vary considerably from one project to another. In many cases, a prototype build is only a few parts used to verify form, fit and function, with engineering trying to determine if something actually works.

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Flex Circuit Specifications for Commercial and Military Applications

09-30-2016

Applications across the various markets for printed circuit boards can have significantly different specifications and performance requirements. Circuits for toys and games logically have lower performance requirements than those used in medical devices. IPC 6013 is an industry-driven specification that defines the performance requirements and acceptance features for flexible printed circuit boards.

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All About Flex: Lead-Free Soldering Flexible Circuits

09-23-2016

Ever since the European community adopted the RoHS directive in 2006, the U.S. electronics industry has been steadily increasing its use of lead-free solder. Medical was the first U.S. industry to go totally lead-free. Today, a significant percentage of electronics soldering is done with lead-free solder.

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All About Flex: FAQs on RoHS for Flex Circuits

09-02-2016

In 2003, the European Union (EU) adopted a standard called the Restriction of Hazardous Substances (RoHS), which restricts the use of certain materials in electronic products and electronic equipment. The intent is to reduce the environmental impact of known hazardous materials and has driven changes in manufacturing processes and materials used to manufacture a wide array of electronic products.

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2015

All About Flex: Embracing the Mess

12-03-2015

Marketing in the world of printed circuits is an important discipline, but I have learned it is better to be prepared with a nimble reaction than to expect the marketing department to consistently be successful in predicting the future. The path to the goal is often achieved much more quickly by making an early decision followed by a course correction rather than waiting for all the information.

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All About Flex: Flexible PCB: What’s in a Name?

11-12-2015

Flexible PCB is a common term that is synonymous with flexible circuits. While the term “PCB” is generally used to describe rigid printed circuitry, “flexible PCB” is a little contradictory because “boards” aren’t really flexible. Some companies, like All Flex, design and manufactures flexible PCBs, but not rigid PCBs. There are many similarities between the two, but also significant differences.

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Plated Through-holes in Flexible Circuits

10-29-2015

There is probably no more important feature than the plated through-hole (also called via or via hole) with regard to the reliability and integrity of a flexible circuit. The through-hole provides electrical connection between insulated layers and enables electrical functionality on double-sided and multilayer flexible circuits.

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Testing Flexible Circuits, Part 3: The Completed Flex Circuit

10-15-2015

Most flex houses perform a variety of tests on completed flexible circuits. The type, frequency, and complexity of these tests vary with customer and application. Test requirements are generally defined by the customer, but input is often solicited from the supplier during the quote process.

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Testing Flexible Circuits, Part I: Requirements and Procedures

09-17-2015

In this first of a three part series regarding tests for flexible circuits, I will examine overall requirements and procedures; the second installment will focus on raw materials, and the third and final part will focus on testing for bare flexible circuit and circuit assemblies.

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Catching Up to Yesterday

09-02-2015

Recently, KPMG, an international consultancy that operates as a network of member firms offering audit, tax and advisory services, came out with their 6th annual survey of manufacturing executives focusing on global manufacturing trends.

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The Butterfly Effect

08-20-2015

If a random initial disturbance from the wings of a butterfly can have a dramatic effect, just think what can be accomplished with intentional acts aimed at making sure our customers are receiving proactive attention.

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Is Wearable Technology Just a Fad?

08-13-2015

Wearable technology is in its infancy. The industry needs to mature and go back to basic marketing—finding a need and filling it. Flexible circuits have been around since the mid-1960s and have been successfully filling needs. Flexible circuits are ideal for wearable technology because they are thin and lightweight. As the marketing matures, the applications will come and flexible circuits will be there to fill the technical needs.

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Unique Single-Sided Flexible Circuits

08-06-2015

The number of iterations, sequences and combinations possible when manufacturing a flexible circuit can create unique product features to reduce hand assembly of wires, create switch contacts, or eliminate connectors. With minor alterations in basic processing steps, a flex circuit applications engineer can often imagine and configure a dramatically different flexible circuit.

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Agricultural Drones and Flexible Circuits

07-28-2015

According to MIT Technology Review, one of theTop 10 breakthrough technologies last year was the agricultural drone. I focused on drones in one of my recent columns, Flexible Circuits and UAV Applications, which briefly mentioned agriculture as one of the uses for drones.

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