During the lifetime of an electronic product, it is likely that at some point it will be dropped. The total cost of ownership for the end user of the product depends upon how the product endures that drop.
We examine the ruggedness, or resistance to damage, of electronic products when dropped. Beyond that first drop, most products are dropped on multiple occasions.
The intensity of the drop can vary from extreme (occurring less frequently) to the more commonly occurring lower intensity drop, referred to as a “tumble”.
Since no established group of standards that electronic devices are tested to withstand exists today, it is important for companies to understand the standards that can be applied, and the major factors that determine the ruggedness of an electronic product.
Equating the methods used in specifying resistance to damage to a customer’s use cases is critical in evaluating if the rating or test method is a valid measurement or guide to how the product will survive with actual use.
When evaluating an electronic product’s ruggedness when dropped, it is important to understand:
- The various standards of drop testing, along with their limitations.
- How the surface to which the product is dropped can greatly affect the cumulative damage a product may sustain.
For the frequent low-level drops that a product may sustain, how the product may be tested to ensure a level of resistance to damage from tumbling.
What is Drop Testing?
Drop testing evaluates a product’s ability to withstand being dropped. Since accidental drops are likely to occur during a product’s lifetime, it is important that a product be designed to withstand a minimum defined number of these impacts. (Note that this does not mean that devices are designed to be dropped intentionally.) Prior to testing, the number of drops, height of the drops, and surface to which the product is dropped must be specified.
During the test, a product is dropped in a “free fall” manner a set number of times, from a fixed height, to a flat surface. (Objects are dropped from a stationary position and are not thrown or directed.)
The test unit is placed in a specified orientation (for example, display down, display up, on its side, etc.) for each drop.
After each drop, the unit is examined for damage. Units exhibiting a major loss in functionality, such as problems with powering on, capturing data, and allowing data entry, after drop testing do not pass the test.
Several factors increase the severity level of testing, including increasing the required number of drops, height above the surface, the hardness of the drop surface, and decreasing the temperature of the unit during a drop (as product becomes more rigid with respect to impact).
What are the Drop Standards?
Various drop standards or drop specification references are often used when testing devices. These include Zebra internal drop standards, U.S. Military Standard (MIL-STD), and competitive drop standards/specification references.
Zebra Internal Drop Testing
Zebra’s internal drop testing standards require that:
- A unit is dropped 36 times - 6 times per side.
- The test is repeated on 3 different units across the device’s operating temperature range (at high, low, and room temperature).
- Test units are operational (powered on) when dropped.
- Drop heights range from 4 to 8 feet.
If the device powers off or reboots and data is lost during testing, the device is deemed to have failed the drop test.
What is Mil-Std-810 certified?
U.S. Military Standard, MIL-STD-810G, defines a process by which devices are dropped 26 times, on all faces (sides), corners, and edges.
- Distributed over 5 test units, the unit test includes 8 corner drops, 12 edge drops, and 6 face drops.
- Units are dropped at test method-defined temperatures.
- Units are non-operational (powered off) for the drop test.
Different Options within MIL-STD Drop Testing and Their Effects on Products
MIL-STD provides options for passing the drop test. When a product is specified to meet MIL-STD-810G drop standards, it is important to compare the product specifications directly to the many options of the military standard to see the exact details of the drop tests, and therefore better understand the severity of the testing; and consequently, the true ruggedness of the device.
Various options within MIL-STD drop testing affect the severity of a test, including:
- Height of Drop - devices can be dropped from varying heights within MIL-STD specifications. Higher drops produce greater impacts.
- Surface Material - surface material to which units are dropped, such as plywood over concrete, vinyl tile over concrete, concrete, or steel. Harder and rougher surfaces produce higher impacts during drop tests.
- Temperature—drop tests can be performed at temperatures above the operating temperature of the device or just at room temperature, depending on the military specification option picked. Drop tests occurring over a wider temperature range are more difficult to pass because components are more prone to physical failures at temperature extremes (such as cracking at cold temperatures and swelling at hot temperatures).
Competitive Drop Standards or Specification References
May specify more than just the drop height:
The drop surface, number of drops, and temperature range may be included or excluded from the specifications.
The temperature range of drop tests can also be omitted.
Factors typically not defined include:
Number of units dropped to pass the test.
Definition of the unit’s power state (on/off)
Drop Standards Summary
Not all drop specifications are the same, when assessing drop performance, one should look at these factors:
What drop standards (for example, Zebra internal or MIL-STD810G) or specification references are used
Drops over a range of temperatures
Number of drops, if listed
Whether a tumble specification is also defined.
We have created a more detailed guide about Drop-testing.