Using Supply Chain FMEA to Improve PCBA Reliability

April 23, 2020 Cadence PCB Solutions

Key Takeaways:

  • Learn about what the failure mode and effect analysis processes can do for PCB design
  • Discover the implications of FMEA on supply chain management
  • Understand FMEA in DFM best practices

 Paradigm for FMEA

FMEA Steps

 

Today, there seems to be a love-hate relationship with artificial intelligence (AI) or at least its utilization in machinery. Some of us can only see how AI can make our lives easier and allow us to accomplish feats once only imagined. Then there are those of us who are afraid that we will eventually create a superior race of machines that may have no use for us. I have to admit the thought of extinction is scary. Yet, it would probably take a failure-proof machine to ascend to that level of independence. 

And as we PCB developers know all too well, the potential for failure is always lurking around any circuit board design which is the root of virtually all mechanizations, intelligent or not. During development, the iterative prototyping process is most effective for eliminating errors that may translate into manufacturing defects and/or low production yield rates. Successively making it to production is not the end of the evaluation of your boards. Instead, reliability engineering, which is concerned with your PCBA’s operation over its lifecycle, should be employed.

One of the methods to optimize your board’s reliability is to institute failure mode effects analysis or FMEA. FMEA provides a systematic process of managing risks that can lead to failure. As the success of operation for your boards depends heavily on the components and materials used, supply chain FMEA is important for board reliability. Let’s see why this is the case by exploring how applying FMEA to your supply chain can improve quality, performance and reliability. 

What is FMEA for PCBAs?

In the broadest terms, FMEA can be defined as a means of evaluating the quality of a process by identifying, monitoring and measuring a set of risk factors and the impact they have on the success of the process. For this technique to be effective, it must be accompanied by an implementation strategy to mitigate the risks. For PCBA design and manufacturing, this is often referred to as risk management. Irrespective of the specific terminology you choose to implore to describe it, the objective is to improve your process such that any risk occurrence is quickly identified and controlled. 

Specific risks and associated controls are based on the process under analysis. Common utilizations for circuit boards include design, board fabrication, component selection and utilization, PCB assembly or collectively, PCBA development. FMEA is also used to optimize yield rates for low and high-volume board production. An important aspect of the overall process from design through production that is not as often scrutinized, except for critical systems; such as medical devices and aerospace, is the supply chain. We address this oversight in the next section. 

Using FMEA for Supply Chain Management

When FMEA is applied to your supply chain it can be defined more explicitly as below.

Supply chain FMEA can be defined as the systematic review and design analysis of identified supply chain items that have the potential to negatively impact your process or its results.  

By undertaking this overview of your supply chain you are instituting better management and control of the quality of components and materials that are used to build your boards. As a consequence, the boards produced are much more likely to function as intended for their expected lifecycle. To be effective, FMEA for your PCBA supply chain should follow a well-defined paradigm or set of steps; such as those listed in the table below.

 

STEPS FOR PCBA SUPPLY CHAIN MANAGEMENT

FMEA Step

Description

PCBA Supply Chain Example

  1. Identify risk types

For this step, the goal is to create a finite set of categories or types into which all of the risks can be placed.

Components, board materials.

  1. Identify potential risks

These are the items that occupy the subcategories or risk types and should be as complete as possible.

For components, there may be ICs, connectors, passive devices, etc. Materials may include laminates, dielectrics, coppers, solder masks, etc.

  1. Rate each risk

Here each item is ranked according to the severity of its effect.

As an example, the effect on performance of different copper roughnesses is less critical than the CTE of a dielectric.

  1. Quantify each risk

Quantification simply means to create a numbering system based on rating that clearly identifies how the risk can affect the process (e.g. acceptable, minimal, critical, etc.).  

A bad or malfunctioning IC is critical for the board’s operation. However, a bad connector is less so as it can be avoided or easily replaced.

  1. Analyze risks

For all failure modes (e.g. malfunction, short, board catches fire, etc.) determine what risk(s) could contribute or cause it.

As an example, a short could be caused by a bad component, overcurrent from an outside source, etc.

  1. Develop controls

Generate actions to mitigate the risks or bring the process back to an acceptable level.

Control may be the removal and replacement of a component, choice of a different material or require redesign.

  1. Apply control and reassess

If an event occurs, apply the appropriate control(s) and analyze the process again. This may need to be repeated more than once for different risks and controls.

If the risk is critical, the effectiveness of the control should be applied on a small number of boards to ensure its effectiveness before returning to full-scale production.

As indicated in the table, if the risk is critical and is rendering boards unusable in the field, this issue should be solved before large numbers of PCBAs are produced and redeployed. Lower level risks may not require this extreme level of mitigation. Although the effectiveness of your supply chain FMEA can be determined to a great extent by post-production assessment, there are design steps that should be included that can be as valuable.  

How Supply Chain FMEA Can Improve Design Quality and Board Performance

An obvious first step in managing your PCBA supply chain is the selection of your components and materials. In many cases, you can rely on your previous experiences using some components or working with some suppliers. Invariably, you will need to often select new components for which you are unfamiliar with their quality, which can be a major cause of electronic circuit failure. Instead of spending countless hours searching online or worse yet, simply taking a stab in the dark, it is much better to rely on an established parts library as shown below. 

Using PCB Librarian

Cadence PCB Librarian

 

The PCB Librarian, shown in the figure above, is just one tool available with Cadence Allegro that allows you to leverage automatic and real-time component research data from trusted sources. By employing advanced PCB design capabilities; such as this database you can be assured that your selection process is aiding in the quality of FMEA supply chain management. 

Although all designers are concerned about reliability, many overlook the importance of supply chain FMEA and its impact on quality, performance, and reliability. If you use Cadence’s PCB Design and Analysis package, then you have access to Allegro’s advanced capabilities including data and process management tools that simplify the selection process of supply chain items. 

If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts

About the Author

Cadence PCB solutions is a complete front to back design tool to enable fast and efficient product creation. Cadence enables users accurately shorten design cycles to hand off to manufacturing through modern, IPC-2581 industry standard.

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