Let's Talk Testing: You’re in for a (Thermal) Shock!

Printed circuit board history stretches back to the early 1900s, with real promise shown in the industry after World War II. Through the 1940s, 1950s, and 1960s, PCB construction really started to progress when fiberboard and wood were replaced with resins and laminates, and rivets replaced early plated through-holes.

As the industry grew, IPC, the worldwide printed circuit board trade association, had its first meeting in the late 1950s. It was around this same time that the idea of testing printed circuit boards became a real discussion topic, and one of the first tests explored for helping to determine the robustness of a PCB’s construction was thermal shock.

The premise is quite simple: apply stress and strain to the PCB via exposure to hot and cold temperature extremes. One of the first methods developed for this type of testing, but geared more towards any type of test sample, was MILSTD-202, method 107—Thermal Shock. The method’s purpose statement provides a perfect depiction of what the test was designed to do: “This test is conducted for the purpose of determining the resistance of a part to exposures at extremes of high and low temperatures, and to the shock of alternate exposures to these extremes, such as would be experienced when equipment or parts are transferred to and from heated shelters in arctic areas.”

Further inspection of the test document describes thermal shock testing with the use of both environmental chambers as well as liquid baths. For the latter topic, the method even provides some guidance as to what type of fluid can be used, as water is obviously not a suitable fluid for all the temperature test conditions that are listed. Also in the document is a table which provides some knowledge about dwell times.

The dwell time is the duration that the test specimen is exposed to a given temperature extreme and should be sufficient in length to ensure that the test specimen reaches the desired extreme temperature.

The table itself provides some guidance on this topic relating the dwell time to the test sample’s weight.  I would highly recommend perusing this table to educate yourself on the industry-accepted durations.

To read the full version of this column which appeared in the April 2017 issue of The PCB Magazine, click here.

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2017

Let's Talk Testing: You’re in for a (Thermal) Shock!

04-26-2017

Printed circuit board history stretches back to the early 1900s, with real promise shown in the industry after World War II. Through the 1940s, 1950s, and 1960s, PCB construction really started to progress when fiberboard and wood were replaced with resins and laminates, and rivets replaced early plated through-holes.

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Let's Talk Testing: How Strong is Your Foundation?

02-28-2017

In my December 2016 column, we discussed the idea of supplier surveillance and that one should put into place some type of doublecheck to ensure that you are getting exactly what you’ve asked for, designed, ordered, etc. To take that idea a step further and to circle it back to the main industry we are discussing here, let’s look at some of the testing that one might do under a supplier surveillance program as it relates to a standard printed circuit board—the foundation of most electronics in today’s world.

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Got Whiskers?

01-10-2017

The tin whisker phenomenon is an issue that has plagued the electronics industry for many years now; however, with even more sectors of the industry now looking to shift or go lead-free—eliminating or limiting lead—in their processes and products, focus on this potentially devastating issue appears to be on the rise once again.

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2016

Let's Talk Testing: Are You Getting What You’ve Asked for?

12-15-2016

A lot of things are taken for granted nowadays. Even in our everyday lives, we order things, but are we always getting exactly what we’ve ordered? What we’ve paid for? Maybe… hopefully…but maybe not. In the testing world, we call this double-checking “supplier surveillance,” and it can influence and affect anyone and everyone in the printed circuit board and printed circuit assembly supply chain.

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Vias for Dummies

11-15-2016

In simple terms, a circuit board is but a composition of things designed to be connected and not. The number of layers and number of connections make no real difference as the geometry shapes the landscape.

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Don’t Reinvent the Wheel—Find an Expert!

10-15-2016

Back in the day when I was an engineer fresh out of college, I quickly learned that experience is the solution to many problems. Now that being said, experience comes in many forms…it could be knowledge learned from a textbook, it could be an observatory comment jotted down in a notebook, it could be a conversation with a co-worker or colleague, or it could be an Internet search that finds a scholarly technical article, etc.

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Does your Product have a Military Application?

09-15-2016

Just like any other industry segment within the circuit board world, the military sector has its own share of documents…and likely many more than most! These documents have been developed over the years to guide, shape, and test anything and everything that might go into a jet fighter, a radar system, a warship, a weapons system, etc.

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Welcome Your Product to the Real World!

08-15-2016

The days, weeks, and (sometimes) years that go into a product’s development usually are incomprehensible to the lay person. Like laws and sausages, no one wants to really understand what has gone on behind the scenes to make your “thing” a reality. They just care that your widget makes their life easier and/or more enjoyable!

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Let's Talk Testing: Seeing is Believing in Fractographic Analysis

07-13-2016

One of the more common types of failure analysis is the investigation of something that has broken. For this column, we will be discussing a broken material, or, more commonly, a fractured or cracked material.

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