Environmental Conditioning and Accelerated Testing

CALCE offers a wide range of environmental testing chambers where the temperature and humidity can be precisely controlled to investigate the impact of various environments on electronic products and systems.

Temperature cycling tests are used to test the durability of a package undergoing extreme temperature variations over a given period of time. This test exposes the package to mechanical fatigue induced by cycles of thermal expansion. The dwell period is important because it allows the sample load to reach equilibrium and for stress relaxation to occur.

Humidity cycling and temperature-humidity cycling are used to assess the effect of swelling from moisture absorption on product reliability. The cyclic nature of these tests accelerates damage accumulation from periodic moisture absorption and desorption during changes in environmental humidity.

The temperature-humidity-bias (THB) test is used to test for moisture induced failures. The test requires the devices to undergo a constant temperature, elevated relative humidity, and electrical bias (constant or intermittent, based on device type). Voltage cycling may be required to prevent the device from heating up and preventing moisture effects from occurring.

A HAST environment is defined by high temperature, high humidity, and high pressure. These three factors categorize the HAST chamber as a destructive environment for standard high reliability testing of integrated circuits. The maintenance of high humidity at temperatures above 100^oC allows for extreme acceleration, up to a factor of 50, of corrosion mechanisms due to moisture.

The CALCE High Altitude Simulation (HAS) chamber, CALCE Mixed Flowing Gas (MFG) chamber, QUALMARK Highly Accelerated Life Test (HALT) chamber, and other temperature/humidity chambers are also available.

HALT and HASS Testing

By combining temperature, temperature change, and multi-axis vibration, accelerated tests using high rate temperature vibration chambers can rapidly identify process defects and expose design weaknesses in a wide range of electronic products. Using well-defined acceleration factors developed at CALCE, highly accelerated life tests (HALT) provide assessments of lifetime and MTBF, reduce product development cycle time, and increase confidence in the product's life-cycle reliability.

The high-rate temperature vibration chamber is capable of temperature ranges of 150^oC to -100^oC at a temperature rate of change of 60^oC/minute (see below). Thermal cycling is achieved by convection heating and liquid nitrogen cooling. The chamber is also equipped with four pneumatic actuators capable of providing simultaneous repetitive shock vibration (RSV) stresses on fixtured test articles across a wide frequency range. The vibration controller is equipped with several time-domain, frequency-domain and fatigue analysis software tools. The spectral distribution of the RSV shaker is fixed by design but can be altered to a limited extent with suitable load train and fixture design.

Test setups involve the use of thermocouples to obtain the temperature distributions across the specimen, accelerometers and strain gages to capture deformation histories of the specimen. The number and strategic placement of vibration sensors is determined through preliminary modal analysis of the CCA. Transient event detectors are used for detecting and monitoring failures.

High-temperature storage test accelerates temperature-induced failures such as interdiffusion, Kirkendall voiding, and depolymerization. In electrically programmable read only memory (EPROM) devices, the test accelerates charge loss from floating gates in the device which is limited by gate oxide layer defects. Devices are stored in a controlled elevated temperature (typically around 150°C) for extended times (of more than 1000 hr) without electrical bias. Interim electrical parametric measurements and final measurements are conducted at the conclusion of the test. The electrical measurements include contact test, parametric shifts, and at-speed functional tests. Damage, such as package cracking, junction thermal resistance increase, or depolymerization, may also be considered a failure.

The ESPEC Highly Accelerated Stress Test (HAST) chamber, High Altitude Simulation (HAS) chamber, CALCE Mixed Flowing Gas (MFG) chamber, ESPEC Liquid-to-Liquid Thermal Shock chamber, and other temperature/humidity chambers are also available.

*Inert gas environment capability

The High Altitude Simulation (HAS) chamber recently acquired by CALCE is a one-of-a-kind piece of equipment. It is designed to replicate environmental extremes that an airplane may normally encounter during operation. From a hot, wet tropical environment at sea level to the cold, dry extremes 70,000 ft. into the upper atmosphere. The altitude test machine has the ability to simultaneously change temperature, pressure, and relative humidity.

The Mixed Flowing Gas (MFG) Chamber exposes connectors, contact surfaces, and other electronic equipment to a mixture of pollutant gases in a controlled temperature and humidity environment. It's purpose is to accelerate failure mechanisms seen during a product's long-term use in an office, light industrial, moderate industrial, or heavy industrial setting. For more information on CALCE's MFG Chamber and its capabilities, please follow this link for a detailed introduction.

CALCE MFG Chamber Capability
The CALCE center provides quality services to electronic applications that require qualification test by MFG chamber located in CALCE research center at the University of Maryland. It is capable of 3 or 4 corrosive-gas-testing. Figure 1 shows the photo of this Mixed Flowing Gas testing system. Table 1 lists the capability of the MFG chamber.

Figure 1: MFG Chamber Located in CALCE Center at the University of Maryland

Table 1: CALCE MFG Chamber Capability

The ESPEC Highly Accelerated Stress Test (HAST) chamber, High Altitude Simulation (HAS) chamber, QUALMARK Highly Accelerated Life Testing (HALT) chamber, ESPEC Liquid-to-Liquid Thermal Shock chamber, and other temperature/humidity chambersare also available.

Flower of Sulfur (FoS) tests are used to examine the susceptibility of test articles to sulfur based corrosion.  Defined by ASTM-B809-95 (2018), which was originally approved by ASTM in 1990, the  Standard Test Method for Porosity in Metallic Coatings by Humid Sulfur Vapor ("Flower-of-Sulfur") was developed to test the porosity of metallic coatings over silver, copper, and copper-alloy substrates.   With the advent of lead-free electronics, variations of the original FoS test have been developed and reported in the literature.  In particular, the test has been used to successfully demonstrate silver corrosion weaknesses that have escaped mixed flowing gas (MFG) tests. 

The traditional FoS test uses a glass or acrylic desiccator to define the control volume. A solution of KNO₃ and deionized water to create the humidity source, and powdered (granular) sulfur as the sulfur source. A dish of granular sulfur is placed in the bottom of the desiccator along with a dish of KNO₃ solution. Test specimens are suspended over the dishes within the desiccator and the desiccator is placed in oven to control the ambient temperature. The lid of the desiccator must be sufficient to create a moisture seal to maintain a controlled humidity level within the desiccator An schematic image of the test can be found below.