Dan’s Biz Bookshelf: ‘Costovation: Innovation That Gives Your Customers Exactly What They Want—And Nothing More’
The Right Approach: ‘Twas the Night Before Christmas (Harley-style)
It’s Only Common Sense: Dear Santa, Here’s My Sales Wish List
All About Flex: Taguchi Design of Experiments and Flexible Circuits
July 14, 2016 | Dave Becker, All FlexEstimated reading time: 4 minutes
Reducing variability in a process, or a sequence of processes, can require a significant and structured amount of work and analysis. One must develop an understanding of critical variables and determine methods to control them. Statistically based experiments are often needed for proper analysis.
Classical Design of Experiments
One strategy is to use classical design of experiments (DOE).
With DOE, the technical team needs to first identify variables that are suspected to have a significant impact on the output. With best estimates of critical variables, the methodology then defines a high point and low of each identified variable. Variables don’t necessarily fall into “high” and “low” categories. They may include options like bake or no bake, alternative surface finishes, material types, etc. A series of experimental runs are designed that have variables run at the high point and a low point in combination with all the other variables low and high. The output of the experiment (i.e., the consequence of the variety of inputs), is best if it can be defined numerically.
The table below illustrates a simple two variable experimental design.
The design above is called full factorial because every combination of high and low variables is run. Of course with two variables, only four experimental runs are required to test every combination of high and low. For three variables, eight or 23 runs are required. A four-variable experiment would require 16 unique runs.
A key requirement for proper experimental design is to randomize the experimental order. This avoids results being contaminated by other conditions that were not controlled during the experiment. Randomizing the order of runs reduces the risk of built in experimental bias confounding the results.
A full factorial experiment provides the main effects of each variable plus all the interaction effects.
Designed experiments are valuable, but disruptive for three primary reasons:
- They should be performed on production equipment
- Proper examination of variables may involve a large number of experiments; if six variables are to be examined, a full factorial experiment would require 64 different runs
- Randomization adds set-up times and cost in a highly capitalized production environment
A more realistic type of DOE is called fractional factorial. Fractional factorial experiments are designed to only find out the main effects and major interactions; as such, they require fewer runs. Many good reference documents are available to assist with DOE layout, statistical interpretation, and factorial design.
Taguchi Design of Experiments
Taguchi design of experiments is a variation of fractional factorial experiments, but with a one major difference. It addresses the fact that it is not realistic to control every single variable that might affect the process. Outside temperature, humidity, time of day, raw material supplier and operator are just a few examples of variables that are either impossible or highly impractical to control. If the experiments are being done in production, they may need to be spread out over several weeks so production schedules can be accommodated. Randomizing the experiment in a full scale production environment is often prohibitively expensive.
The Taguchi method allows for the reality faced when conducting designed experiments in production: it is often not practical to properly randomize an experiment. So in addition to all the critical variables tested, another variable, noise, is allowed and defined. The noise contains all the variables that are not controlled. The high level might be the noise variables set at one realistic extreme and the low level might be all the noise variables set the other realistic extreme. One of the goals of the experiment is to determine what variables and variable settings yield the most robust results. These are settings where there is zero interaction effect with the noise variable.
Page 1 of 2
Share on:
Suggested Items
Global PCB Connections: Following DFM Rules Leads to Better Boards
12/18/2024 | Jerome Larez -- Column: Global PCB ConnectionsAs a PCB field applications engineer, ensuring smooth communication between PCB designers and fabricators is one of my frequent challenges. A critical part of that dialogue is design for manufacturing (DFM). Many designers, even experienced ones, often misunderstand or overlook important DFM considerations. They may confuse design rules with manufacturing minimums, leading to technically feasible designs that are difficult or costly to produce. In this column, I will clarify some common DFM guidelines and help designers understand the difference between “design rules” and “minimums” while sharing best practices that will simplify the production process and ensure the highest quality PCB.
Sayonara to the Last Standing Copper Foil Plant in North America
12/17/2024 | Marcy LaRont, I-Connect007In July 2021, PCB007 Magazine published an interview with Michael Coll and Chris Stevens of Nippon Denkai about the new acquisition by Nippon Denkai of the last-standing ED foil manufacturer in North America. The plant in Augusta, Georgia, was formerly owned by Oak Mitsui, Inc. and had been purchased by Nippon Denkai the previous March, after which significant investment was made with the expectation of providing more jobs.
SCHMID Group Unveils Enhanced InfinityLine H+ for Electroless Copper Deposition
12/16/2024 | SCHMID GroupThe SCHMID Group, a global leader in high-tech solutions for the electronics industry, proudly announces significant updates to its flagship InfinityLine H+ Electroless Cu system. Specifically designed for the production of high- performance advanced packaging applications using mSAP and SAP processes, the system reflects SCHMID’s expertise in horizontal electroless copper deposition.
OKI Develops PCB Technology with Stepped Copper Coin Insertion to Achieve 55 Times Better Heat Dissipation in Outer Space
12/12/2024 | BUSINESS WIREThe OKI Group printed circuit board (PCB) business company OKI Circuit Technology has successfully developed multilayer PCB technology with stepped copper coin insertion to achieve 55 times better heat dissipation compared to conventional PCB. The stepped copper coin is offered in two types, circular and rectangular, to suit the shape of the electronic component mounted on the PCB. OTC is working to develop mass-production technologies with the aim of introducing PCBs incorporating this new technology into markets for compact devices or devices used in outer space or other environments where air cooling technology cannot be used.
Fresh PCB Concepts: PCB Plating Process Overview
12/12/2024 | Team NCAB -- Column: Fresh PCB ConceptsIn this installment of Fresh PCB Concepts, Mike Marshall takes the helm stating: PCBs have been the platform for the interconnection of electronic components for decades. Because of process costs and other constraints, such as mechanical properties or size limitations of the alternatives, PCBs will remain the standard low-cost interconnection technology. Rapidly increasing performance and functionality requirements of wireless and high-speed devices have challenged the development and implementation of new manufacturing solutions.