Common Sense Approach For Good Testing
by Jeffry A. Schutt

There are many pitfalls to avoid, especially for the entry level engineer, when planning and conducting tests. Today’s turnkey test equipment enables engineers and technicians, with limited testing experience, to conduct tests relatively quickly and efficiently. However, while computers and menu driven software have enabled testing laboratories to become increasingly more efficient, as far as testing productivity is concerned, a void has been created. This void is the lack of in-depth knowledge of testing that exists in many laboratories. The downturn in military business, corporate downsizing, and attrition have resulted in many of the test industry’s best engineers leaving for greener pastures. Consequently, many entry level engineers and technicians are being thrust into the position of learning and understanding the nuances of testing.

It is one thing to go through the motions and to setup and program a test. However, it is another thing to understand the rationale for conducting the testing and the details of conducting the testing. It is still another thing to be able to interpret the data and to extract meaningful conclusions from the data. Consideration must be given to numerous variables, in order to conduct an effective test and to obtain the desired results. This article will present these issues and will outline a common sense approach for good testing.

A good test begins at the planning stage. Understanding the test objective, and the selection of appropriate test procedures and requirements, are considerations that should be given as much emphasis as the actual testing itself. Test tailoring, when appropriate, and when permitted, should be employed. Certainly, test tailoring should not be thrust upon a neophyte test engineer. Test tailoring is something that should be left to knowledgeable, experienced testing experts. The testing industry is aware of the fact that most degreed engineers coming out of college are not ideally suited for work in a typical industrial or commercial test lab. Much of the knowledge required to work in a test lab, as is the case with many other jobs, can’t be taught in school. Certainly, there is a lot of on the job training that must be done, and experience that can be gained, in the test lab. Valuable knowledge and experience about a particular test program, or about testing in general for that matter, can be gained by being involved in the test planning process. Some elements of the test planning process are outlined in Table 1.

One could argue that planning for testing is the most important phase of testing. There are numerous considerations that must be made, so that a test can be conducted without incident and as efficiently and effectively as possible. Improper planning for a test could result in costly mistakes, in terms of time and dollars.

A good part of the test planning process is often left to engineering managers and contracts people. However, the test engineer must be kept in the loop on issues pertaining to the test planning process. By keeping engineers in the loop during the test planning process, appropriate feedback can be provided regarding issues such as test feasibility, time, cost, and effectiveness. This feedback loop is extremely helpful to engineering management and contracts people, when planning testing. This feedback loop is also extremely helpful to the test engineer, when preparing for testing.

Once a test has been properly planned, it is important to prepare for the testing. Even before samples for test are received, a great deal of work must be accomplished. It is important that everyone involved understand the test objectives. It is also necessary to determine what data is to be gathered. Data traceability is one aspect of testing that should not be overlooked during the planning and preparation stages of testing. All samples should be uniquely numbered and all data should be traceable to those samples. Data should also be traceable to a particular step or condition in the testing program, during which the data is to be taken. In addition to traceability, the baselining of samples is something that should not be overlooked. Baselining of samples involves, at a minimum, a detailed visual exam, to identify the starting condition of the test samples, prior to the point at which they are placed into test. Baselining of samples can also involve parametric, functional checks of the test sample’s operation and performance. By knowing how a sample performs "Out of the box," prior to the application of adverse environments, the test engineer can have data that can be used for comparison purposes later on in a test program. Appropriately identifying samples for data traceability and baselining the samples are two important, preliminary steps that are necessary for a good test. Some general parameters that should be recorded for data traceability appear in Table 2.

In order to demonstrate the nuances of a typical test program, a specific example of a vibration test will be utilized. One might think that conducting a vibration test is as simple as following a recipe in a cook book. However, there are so many ingredients that can go into a vibration test. It is critical to specify each of the ingredients (parameters) and to understand when and how to use the ingredients. Some of the technical considerations for conducting a good vibration test are listed in Table 3. Issues such as accelerometer location, fixturing, test levels, monitoring requirements, and others all must be considered, when developing and conducting a vibration test. Failure to specify and understand these issues could result in an improper test being conducted. Vibration testing is especially sensitive to variability from one test to the next, because of issues like accelerometer placement and fixturing. By varying these parameters, a completely different test could be conducted, even if the same test levels are to be applied. It is absolutely essential that the test engineer understand the effect that these parameters can have of the outcome of a vibration test.

The Institute of Environmental Sciences and Technology is in the process of formalizing a number of recommended practices that should help the test engineer better understand the nuances of conducting a good vibration test. While there are many standards and specifications available, which describe various vibration environments, there is a lack of guidance available to the test engineer in the form of recommended practices. These recommended practices are being generated to help test engineers correctly implement the numerous standards and specifications that exist. Some of the recommended practices that the IEST has developed, and is developing, are listed in Table 4.

The above dialog and associated figures present some of the details to which the test engineer must pay attention, for good testing to result. However, there is much more to conducting a good test than what is mentioned above. The test engineer has quite a bit of "behind the scenes" activities, which are also necessary for good testing to result. For instance, every laboratory should have a system of procedures and policies for dealing with the myriad of issues that the laboratory confronts on a daily basis. Procedures and policies for the operation of equipment, calibration of equipment, verification of equipment, maintenance of equipment, data gathering, root cause analysis, and a host of other issues should be developed to help insure that an appropriate testing infrastructure is in place for good testing. A list of typical issues, which laboratory procedures and policies should address, is included in Table 5. These types of procedures and policies help to insure consistency and uniformity in the approach to conducting testing. These procedures and policies also help to ensure that equipment is well maintained and calibrated. These types of procedures and policies are generic enough, so that they apply to almost all testing that is conducted in the laboratory. Many such procedures and policies are part of the ISO 9000 and/or ISO Guide 25 requirements. Therefore, if a laboratory is to be ISO 9000 registered or ISO Guide 25 certified, it is critical to have such procedures and policies in place.

Conducting a good laboratory test takes more than button pushing to spit out a number. It takes engineering talent and experience. It also takes effective planning, diligent setup and data gathering, and comprehensive reporting. It also requires that a system of procedures and policies be in place and be followed, so that a consistent and uniform approach to testing occurs. In addition to engineering talent, experience, procedures, and policies; the laboratory needs one other key element for successful testing, and that is common sense. Knowing what your test data is telling you, documenting it, and reacting to it appropriately are the key common sense elements to good testing. Engineering talent, policies and procedures are needed to facilitate the use of common sense.

References:

• "Considerations for Vibration and Shock Testing of Electronic Assemblies," Jeff Schutt, Trace Laboratories - Palatine, IL 60067, 847-934-5300, originally published in "Electronic Packaging & Production," December, 1996, Vol. 36, No. 13, Randolph D. King, Publisher

• IEST-DTE-RP-012 "Dynamic Data Acquisition and Analysis Handbook," Institute of Environmental Sciences and Technology, 940 E. Northwest Highway, Mount Prospect, IL 60056, 847-255-1561

• "Trace Labs Quality Manual", June 30, 1998 Rev., Trace Laboratories-Palatine, IL 60067, 847-934-5300

• IEST-DTE-RP-013 "Shock and Vibration Fixturing", DRAFT, Institute of Environmental Sciences and Technology, 940 E. Northwest Highway, Mount Prospect, IL 60056, 847-255-1561

• IEST-PR-RP-001 "Management and Technical Guidelines for the ESS Process", DRAFT, Institute of Environmental Sciences and Technology, 940 E. Northwest Highway, Mount Prospect, IL 60056, 847-255-1561

  Mr. Jeffry A. Schutt

Jeff Schutt is the General Manager of Trace Laboratories, an independent, diversified, ISO Guide 25 accredited testing facility, which specializes in providing a wide range of testing services to the computer, military, automobile, aerospace, telecommunications, medical, and other industries. He has served as General Manager of Trace, since its inception in 1988, and has directed the laboratory through two facility moves. Trace now operates out of its new 30,000 square foot facility in Palatine, IL, where environmental, electrical, mechanical, materials, electromagnetic compatibility, chemical and failure analysis testing services are provided. Trace also maintains a facility in Baltimore.

Mr. Schutt currently serves as the President - Elect of the Institute of Environmental Sciences and Technology (IEST). He has also served as the Technical Vice-president of the Design, Test, & Evaluation and the Product Reliability Divisions of the IEST. He was General Chairman of the IEST’s 41st Annual Technical Meeting. He was the recipient of the John Martin Outstanding Young Member Award from the IEST and serves on a number of IEST technical committees. Mr. Schutt is also a member of the Society of Automotive Engineers (SAE), the Institute for Interconnecting and Packaging Electronic Circuits (IPC), the Electronic Industries Association (EIA), the American Society for Testing and Materials (ASTM), and the Chicagoland Circuit Association. Jeff also remains active in several industry consortia, which study the reliability of high density electronic interconnects.

Mr. Schutt holds a Masters Degree in Business Administration from the University of Wisconsin and a Bachelor of Science Degree in Physics from Marquette University. He has also completed coursework at the Illinois Institute of Technology toward an Electrical Engineering Degree. He has published widely in the fields of solder joint reliability testing, laboratory quality systems, connector testing, vibration testing of high density electronic interconnects, screening, and accelerated reliability testing.