What is Design for Excellence (DFx) in Manufacturing?

Manufacturers can differentiate a product in terms of quality before the actual production process. DFx is a combination of excellence, Six Sigma, and quality.

"It is trying to get it right the first time; when the product hits the line, the product works, and you have the confidence it's been de-risked and testable. With DFx you have a 99% confidence that it's going to run and that you've nailed it. Building quality into a product when planned and designed delivers cost benefits and customer satisfaction. Nigel Palmer

 

Design for Excellence (DFx) consists of methods, guidelines, and standards for creating better quality products at the concept design phase. Adopting DFx upfront as an integral part of the product development process produces higher quality products, lower product cost, and shorter product development cycles.  

According to HCL Technologies, 70% of engineering changes are due to DFx issues related to manufacturing, assembly, cost & quality. At TT Electronics, the DFx team engages with the customer at the earliest design phase, addresses any issues, and implements "design for excellence" in a systematic approach. In doing so, we are confident that manufacturers products are fabricated flawlessly with high yields and assembled in a less costly, error-proof manner.  

In this guide, you'll learn the characteristics of DFx design versus traditional engineering methods and its influence on the product development cycle. We will also discuss the tools used to reduce the number of design revisions, improve reliability, and more.

dfx-cover

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Chapter 1

Do You Want a Shorter Time to Market? Choose DFx Over Traditional Developing Process 

Generally, traditional engineering methods do not concentrate on the alignment between a product's design team and its production and supply chain teams. The DFx process brings in different people, talents, and resources when there is a challenge designing for a customer. DFx captures everything before production and becomes the liaison between the customer and the design teams. It's a process that takes place in the early design phase with much collaboration between all involved. 

DFx is a general term used in the engineering community as a placeholder for design objectives. The particular "x" is the key to achieving success in the design phase. The concepts represented by "x" commonly used by engineers are Manufacturability, Assembly, Testability, Cost-Effectiveness, Reliability, and Quality.

Getting DFx in the products as early as possible with the software tools commonly used today, allows TT Electronics to simulate a build, see the footprint and what the parts look like.

There are marked differences between traditional engineering design and design implementing DFx. The chart below highlights their main characteristics.

 

tt-artboard-lean-traditional-vs-dfx

 

DFx applies to both new products (allowing for the most significant chance of fixing any issue) and mature, i.e. already developed products. Defects, new parts, or the re-structuring/re-designing a of a PCB often occur with mature products and that's where DFx can make a difference. It gives manufacturers the feedback they need to produce the most reliable product.

They select design features (or discourage needless features) and options that promote cost-competitive manufacturing, assembly, and test practices. In their planning for design, fabrication, and assembly, their goals are to reduce design iterations and number of defects (high yield), and a reduction in rework cost. Their process starts with a detailed product strategy analysis. 

A template for DFx methods could include:

  • Goal specific design methods targeting different phases of a product's lifecycle. The "x" is the area of focus, such as product design specs, supply chain, and testability. 
  • Lean design processes, utilizing lean manufacturing principles to eliminate waste
  • Identification of problems and needs 
  • Analysis for solutions 
  • Optimization for efficiency and performance (for example, a shorter time to market results in fewer development costs) 

The DFx team develops long term collaborative relationships with customers that ensure products produce with high yields and the lowest cost over the product's life cycle. 

They focus on PCB design, bill of materials, life cycle perspective, testability, and more. A strong DFx team includes Test, PCB, and Mechanical engineers.

 

dfx-2-1

 

The common areas for analysis and review are:

  • Design for PCB Fabrication - i.e., finishes
  • Design for Manufacture - soldering, pre and post assembly review
  • Design for Test - physical test access, test coverage analysis
  • Bill of Materials Analysis - component life cycle review, RoHS compliance
  • Box Build - design for supply chain, assembly, serviceability, metal fabrication

Top Benefits of DFx Today

  1. Improved product cost (reduced life cycle cost)
  2. Reduced time to market
  3. Minimised product risk
  4. Increased quality 
  5. Maximised testability
  6. Improved production yields (early prevention of defects)
  7. Enhanced customer satisfaction (improved delivery)
  8. Improved overall operational efficiencies

Challenges if DFx is Introduced Too Late

  1. Testability can be hindered if the design has matured past the point where changes can still be introduced. 

Solution: Introduce DFx early to allow for improvements to be readily incorporated in the product design.

Chapter 2

Influence of Early Product Design 

Innovative design and cost-efficient production go hand-in-hand. Early product design affects the cost, quality, and the product development cycle. It produces the biggest "value added."

Industry expert, Happy Holden, involved in advanced PCB technologies for 47+ years, affirms: 

"Most products' cost is committed at the design stage before the product is manufactured. Many sources quote 75–85% of the cost of a product is committed during the design and planning activities, whereas the actual amount spent only increases during production after the design has been accepted.

Consideration of manufacturing and assembly problems at the product design stage is, therefore, the most cost-effective way available for reducing assembly costs and increasing productivity." 

Since the decisions made during the new product development cycle account for 75-85% of products cost, it is vital that product cost management begins with the onset of product development.

Simon Qiao, CEO at Innorapid Limited, points out that the four main factors affecting product cost include design, material, labour, and management. He emphasizes that product design determines 75% of the product cost.

 

tt-pie-charts-cost-in-development

Figure 1. Pie chart. Adapted from "Importance of Product Design for Manufacturing and Assembly," by S. Qiao, 2018, from https://www.linkedin.com/pulse/importance-product-design-manufacturing-assembly-simon-qiao/ 

 

The cost in design only accounts for 5% of the total product development cost.

However...

Product design determines 75% of the product cost.

 

tt-pie-charts-impact-on-cost

Design 75% Material 15% Labour 5% Management 5%

 

There can be hidden costs associated with omitting early DFx reviews. These costs are associated with re-design, as in re-layout, PCB re-tooling, and re-build costs (which include materials and labour). Other hidden costs are time to market delay, validation testing, re-qualification, management of new build, and obsolete materials.

Product design can determine the defect rate of a product. The higher the yield, the lower the cost. The defect rate is recognized in the product design phase, not in the manufacturing process. Statistically, a process using DFx and Six Sigma is expected to be free of all defects in 99% of all opportunities.

By engaging at an early design phase, manufacturers can prevent unnecessary design and production delays due to PCB fabrication errors, tests access issues, and out of date material. Adding in a vital component review, BOM checks, test review, and final DFx checks delivers cost benefits and overall product success. 

Below is a suggested process flow towards an error-proof approach using DFx.

 

tt-design-for-exellence-process-1 

Chapter 3

Useful DFMA Process Applied Through Product Development Cycle

Design for Manufacture is the most common practice when it comes to design. DFM is the more widely used term among engineers in the field. DFx has come along recently with the rise in testability and testing solutionsProperly planned DFM and assembly enable companies to build quality products in less time with lower production costs.

In the design for manufacturability, questions are raised, and issues addressed, so there are no surprises at the end. It could be considered a second design phase for the manufacturers.

DFM compliments DFA (Design for Assembly). The two together allow a product design to be manufactured efficiently as well as easily assembled. A manufacturer can detect flaws and eliminate waste and manufacturing inefficiency within a product design. The methodology allows for new and improved products to be offered in a shorter amount of time.

DFM extends to testability, design for quality, and repairability. 

Testability features added to the product design allow you to find faults more quickly. Production level tests are useful and efficient in testing printed circuit boards for resistance, capacitance, and sometimes inductance between two points on the circuit board. 

"Environmental and reliability testing are performed during design as well as in manufacturing. The goal is to test whether your product remains reliable in its intended environment over a required duration of time. By accelerating the normal wear of products, we can reveal design defects - and evaluate reasons for a product failure that help you make product improvements." [source]

In the design review, physical and electrical testability reviews of CAD and schematics are performed. Recommendations are based on individual board technology.

Quality testing and procedures are essential when choosing a reliable PCB assembly manufacturer for your electronics design. 

Chapter 4

How to Design Products for Efficiency Within the Supply Chain While Maintaining Quality

Design for Supply Chain 

A product can be developed from the beginning to be supply chain efficient. The idea is to design the new product and its supply chain in a simultaneous manner. Traditionally, the supply chain was an afterthought (created after the product design phase was complete), which would result in longer cycle time and fewer profits.

By collaborating with supply chain engineers early on, productivity can improve and lower costs achieved. Designing to reduce costs for the supply chain is a big step in product development.

In an article written by Heather E. Domin and James Wisner (IBM Integrated Supply Chain), they state:

"By using Design for Supply Chain techniques to optimise products in the design phase before manufacturing even begins, or in some cases after it has begun, supply chain disruptions can be avoided, and costs of change minimised."

They discussed nine DFsc strategies that change the way companies design new products and transform the supply chain.

Here's an overview

  1. Optimise levels of product integration
  2. Leverage industry standards
  3. Minimize premium freight
  4. Design for life cycle
  5. Configure the selected supply chain
  6. Design for demand & supply planning
  7. Minimize inventory costs
  8. Optimize order management
  9. Minimize warranty/service costs

You can read the full article here: Nine cutting-edge strategies that will change the way your company designs new products and transform your supply chain.  

Design for Quality 

As mentioned earlier, approximately 80% of the product cost is determined by design. The truth of the matter is...

Its quality determines a product's fate. Quality defined as the degree of product excellence. 

The Pareto principle (also known as the 80/20 rule) states that, for many events, roughly 80% of the effects come from 20% of the causes.

In essence, 80% of product quality problems can reflect on the design phase, and 20% are caused by manufacturing and assembly. Instilling the Design for Quality in the design process  leads to better quality outcomes.

According to David Garvin, Competing on the Eight Dimensions of Quality, he proposes eight critical categories of quality that can serve as a framework for strategic analysis:

 

quality-1 

1. Performance - the product's primary operating characteristics.

2. Features - physical dimension, weight, etc. The "bells and whistles" of the product

3. Reliability - "free of failure" during the products time

4. Conformance - meeting specific standards

5. Durability - the product's lifespan

6. Serviceability - ease of repair

7. Aesthetics - how the product looks, feels, etc. perceived by a person's five senses.

8. Perceived quality - a perception of the overall quality

Chapter 5

Improving Product Design (DFx) with Analysis Tools  

A great design team designs a product that fulfills the needs defined by the market.

Analysis tools help evaluate and streamline design considerations. This section covers tools (with examples) that reduces the number of design revisions. A printed circuit board DFM analysis can be conducted using a meta graphics tool. Valor seamlessly integrates the entire PCB manufacturing process with one easy-to-manage platform.

At TT Electronics, all of our global manufacturing facilities deploy the same software; which lends an extra layer of security for customers requiring seamless global product transitions. We share specific rules that are set up in the Valor MSS tool. This allows us to see  customers CAD data and merge their materials, components list, etc. to build a virtual PCB in the software. The tool enables us to see the manufacturer's components and to catch potential errors before assembly takes place.

It performs multiple design rule checks on the PCB layout. The result is a virtual comparison of the BOM (Bill of Materials) to the CAD data.

The analysis provided helps:

  • reduce the number of design revisions required to bring a new design to volume production release
  • improve the reliability of a design by locating manufacturing risks ahead of the production process
  • provide the interface between design and manufacture to ensure a smooth transition to production

Common design errors detected by Valor MSS DFM are insufficient solder mask, non-plated thru holes too close to copper routes, or lines too close to a pad. 

Here's an example where we engaged with our customer at an early phase of design.

We were given the opportunity to provide DFM feedback on the pre-routed PCB, and again on three other occasions as the PCB placement and routing developed into the final revision.

pcb components 

Through the analysis, we discovered the components were found to be too close to the pin through the connector. Ideally, a minimum of 3mm copper to copper clearance is required to allow for automated soldering.

We also found "via holes" (see image below) to prevent solder loss during the re-flow soldering process. We suggested the manufacturer consider "plug and capped" via holes. In the plugged vias process, vias will be plugged with solder mask.


via holes

Mask plugging is used to prevent solder from wicking away from surface mount pads (SMD) during assembly. By introducing DFM within the design phase, it can lower total product cost and NPI iterations

Bill of Materials (BOM) Health Analysis / Obsolescence Management

Understanding your Bill of Materials is necessary when trying to keep expenses down. Analyzing your BOM, engineers and manufacturing teams can benchmark existing and competitor products and current pricing. Bill of Materials includes approved vendor list, component quantity, customer part number (CPN), manufacturers name, and part number (MPN) and more.  

Obsolescence management takes into account "the lifespan of all the moving pieces of your complex system with a plan to replace obsolete parts as they age before it becomes a crisis." 

A BOM health management report (BHM) can help manufacturers identify obsolete components, number of years to end-of-life, near end-of-life components, and the ability to suggest close alternatives and more.

"Design for manufacturing tools exists to check design guidelines for electronic circuit boards. The design checkers evaluate a design for clearances, dimensions, and other specific guidelines using the design files. Design rules are built into the design tools and provide immediate feedback when a guideline is violated." [source] 

In Summary

Is your product ready for manufacturing?

It is essential to design for manufacturability, testability, supply chain, quality, and more before the actual production process for efficient processes and a reliable product outcome. Great engineering design practices start with careful consideration of the product requirements up front to reduce the delays and redesign costs later.

There are always variables to consider, but with DFx (design for excellence) you have confidence that the products are reliable, testable, and have a faster time to market. All equates to happier and satisfied customers. 

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We are the Global Manufacturing Solutions group of TT Electronics plc. From design and engineering, to integrated manufacturing of electronic systems, we deliver a full suite of end-to-end solutions to aerospace, defense, medical, industrial and rail enterprises with highly customized, low volume high mix product requirements.

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