Technical

A Salt Spray Test is an accelerated laboratory test providing a controlled corrosive environment to determine the rusting performance of a product in the field.

Salt Spray Testing is a requirement in a wide range of industries such as automotive, military, paint, and research institutions.It can be conducted on bare material as well as painted or coated material.

The well known ASTM-B117 salt spray test standard is commonly used. A solution of sodium chloride is sprayed at an angle between 15° to 30°. The temperature maintained within chamber is constant. The duration of test can be anywhere between 24 hours to 1,000 hours. Samples are rotated at regular intervals to allow even coating of the salt solution. The salt spray solution will put materials in a very harsh environment which will rust the surface and determine the result of damage inflicted by salt as well as a high chloride content.

This test helps researchers and product designers develop products such as paints, coatings, chemical treatments, paint pretreatments applied to metallic coated steel sheet products or any material that can be more resistant to salt damage.

Sustainability is the capacity to endure. It is characterized by the increased success of a product after many cycles of usage leading to its success and popularity therefore benchmarking it under the sustainability phenomenon.

As an end user of environmental test equipment, you will want to consider the benefits of buying a sustainable product obtained though effective equipment planning and procurement. Hastest Solutions helps the end user define their needs and offers cost effective solutions that will benefit the customer in the long run.

Some characteristics implemented into equipment planning and procurement for sustainability are looking for durable and robust products, ease of use and meeting safety standards. The range of products at Hastest Solutions Inc, include but not limited to, temperature humidity chambers, settling dust chambers, blowing sand and dust chambers, HAST (highly accelerated stress test) chambers meet the requirements mentioned above. The HAST Chamber is an example of a robust and durable product. The oldest generation manufactured twenty years ago is still running at optimum performance with need for replacement of basic wear and tear parts only. The temperature and humidity chambers incorporate user friendly controllers for technicians to save time on learning operation of a new unit and increase productivity during usage. Our chambers have met safety and manufacturing standards through third party certifications of compliance and now carry stamp of approval for CSA International (Canadian Standards Association) UL compliance.

There are many definitions for sustainability. Many refer it to a goal but Hastest Solutions Inc constantly tries to improve on sustainability therefore using it more as a guideline or “journey” to the ultimate destination of a quality product. The demonstration lab at Hastest Solutions Inc located in San Jose, CA carries many of the products listed and the sustainability can be experienced even before purchase. Hastest Solutions Inc strongly encourages the user to visit the lab during procurement process.

Temperature and Humidity tests establish how components and assemblies behave in harsh environments involving high temperatures and high relative humidity. The effect that humidity can have on components or assemblies is crucial to the service life of the product. The tests involve constant temperature and humidity, cycling of temperature and humidity, temperature-humidity bias (THB) tests.

Temperature Cycle Testing also referred to as temp cycling, determines the ability of parts to resist extremely low and extremely high temperatures, as well as their ability to endure cyclical exposures to temperature extremes. Two industry standards that govern Temp Cycle Testing are the Mil-Std-883 Method 1010 and the JEDEC JESD22-A104.

THB testing involves the following stress conditions: 1000 hours at 85 deg C, 85% RH, with bias applied to the device. The bias applied is usually designed to simulate the bias conditions of the device in its real-life application, maximizing the variations in the potential levels of the different metallization areas as much as possible. An operational test that evaluates the reliability of devices in humid environments follows Mil-Std-810-F Method 507.3

Environmental test chambers, particularly temperature and humidity chambers are used to test components under test conditions and Mil Standards described above.

In effort to improve the reliability of products, many different industries, just to mention a few, including semiconductor, pharmaceutical, and solar companies turn to HAST testing as a shorter alternative to THB Testing.

The acronym “HAST” stands for “Highly Accelerated Temperature/Humidity Stress Test.” The acronym “THB” stands for “Temperature Humidity Bias.” THB testing takes 1000 hours to complete, whereas HAST Testing results are available within 96-100 hours. In some cases, results are available in even less than 96 hours. Due to the time saving advantage, the popularity of HAST has continuously increased in recent years. Many companies have completely replaced THB Test Chambers with HAST Chambers.

THB (Temperature/Humidity/Bias) holds 85°C/85% RH condition while bias loads are applied to the samples. It has become less useful in recent years due to the improved packaging and passivation materials.

Highly Accelerated Stress Test (HAST) was formulated to decrease the test time needed to get useful results. Due to time constraints on projects, engineers look for a faster solution to learn if their product meets the standards of their particular industry. HAST testing uses a high temperature (105°C), high relative humidity (about 85%), and high atmospheric pressure conditions (up to 4 atm). HAST testing loads the specimen with heat and moisture stresses to find the concealed defects that could cause failure for the user relying on it. In testing products for reliability, defining the test conditions is the primary step. A common standard used for HAST is JEDEC JESD22-A110. Test conditions must meet application conditions in order to make testing relevant. HAST Testing has also in turn become a more cost effective alternative.

HAST is recommended for the shortened qualification of any change that can potentially affect the corrosion resistance of the product. Therefore, a new package and/or a new fab assembly site demands HAST data. HAST is also recommended for changes in the die glassivation, metallization or thin film resistors, as well as changes in the molding compound.

HAST Testing continues to find more applications for accelerated testing of newer materials and products.

A Comparison of HAST to Conventional THB Testing

The use of HAST (highly accelerated stress test) for reliability assessment of nonhermetic packages is driven by reliability improvements in plastic packaging and passivation materials. Conventional Temperature/Humidity/Bias (85/85) testing is inefficient in measuring these reliability performance improvements. HAST is a highly effective and repeatable assessment tool for evaluating plastic package reliability provided appropriate controls are used. Important HAST operation controls such as chamber cleanliness and basic operation constraints are outlined. An SRAM device test vehicle is chosen to study effects of high temp/moisture/bias stressing to allow for easier characterization of HAST and comparison to 85/85 testing.

This paper discusses data comparing HAST to conventional 85/85 testing on 16Kx4 commodity SRAM’s. Data from multiple HAST runs on different lots of the same SRAM test vehicle shows the repeatability of the stress test. Data from the same SRAM part type stressed in 85/85 shows lower comparative accelerations for the same failure mechanisms. Surprisingly, metal-corrosion is not the dominant failure mechanism in these tests. Systematic AC parameter shifts are the predominant cause for failure. A relative acceleration factor for HAST over 85/85 testing is extracted based on AC parameter shifts in plastic-packaged parts succumbing to a moisture-driven failure mechanism. This data provides another example of HAST capability and an indication of the type of failure mechanisms that can be found with today’s plastic packaging materials.

This paper appears in: Electronic Components and Technology Conference, 1994. Proceedings, 44th, Abstract Plus

Electrochemical Migration…Under Highly Accelerated Stress Conditions

Land grid array sockets are used as separable interconnects between printed circuit boards and high I/O integrated circuit components. Metal-in-elastomer land grid array sockets consist of an array of elastomer contacts, a polyimide insulator and a thermoplastic frame. Silver particles are embedded in the silicone elastomer as contact medium to provide electrical paths between a printed circuit board and a component. In order to assess the reliability of this type of socket, biased, highly accelerated stress testing (HAST) was conducted.

The surface insulation resistance (resistance between two adjacent contacts) was monitored, and was found to decrease significantly. Silver electrochemical migration (ECM) was identified as the cause. Both dendrites and film were observed on the polyimide insulator surface as a result of ECM. The dendrite grows from cathode contact to anode on the polyimide insulator surface. The ECM products were analyzed using both energy dispersive spectroscopy and X-ray photoelectron spectroscopy. Silver and silver oxides were detected as ECM products on the polyimide surface after HAST exposure. The potential chemical mechanism of silver electrochemical migration was described based upon the analysis of the ECM products.

Electrical Contacts, 2005. Proceedings of the Fifty-First IEEE Holm Conference on 26-28 Sept. 2005 Page(s):238 – 244

HAST (Highly Accelerated Stress Test) Articles:

Reliability Tests of Ultrasonic Bonding Methods Using HAST and THB

Reliability is one of the most important questions in any application, on both the package (component) and the board (system) levels. The paper describes some life time test methods, equipment and processes for evaluating the most important reliability parameters. It gives a detailed description of the most effective and economical HAST (highly accelerated stress test) and THB (temperature humidity and bias) methods.

The paper presents some new results of using HAST and THB technology for the following fields of reliability and life time tests: reliability analysis of assembled SMD passive components; water addition speed tests. Finally, the paper particularly deals with ultrasonic bonding technology, the bonding and testing machines. It introduces some measurement test results on the bonding force before and after a HAST and THB test.

This paper appears in: Electronics Technology: Meeting the Challenges of Electronics Technology Progress, 2004. 27th International Spring Seminar

HAST Applications: Acceleration Factors and Results for VLSI Components

Results and acceleration factors between several highly accelerated stress test (HAST) conditions and 85 °C / 85% relative humidity tests are given for NMOS EPROM’s (erasable programmable read-only memories) and CMOS RAMs (random-access memories). Two failure regimes exist in time: the earliest is below 25% cumulative failures and is due to passivation defects; beyond that, failures are due to passivation moisture saturation or wear out. Results are sensitive to device/process, passivation integrity, and test apparatus cleanliness. Failure predictions are dependent on which failure regime is used.

This paper appears in: Reliability Physics Symposium, 1989. 27th Annual Proceedings, International

Highly Accelerated Stress Test (HAST) For Low-cost Flip Chip on Board Technology

Flip chip on board (FCOB) technology has been in widespread application. The reliability testing of solder-joints and the delamination between underfill and chip or substrate is still a critical issue for FCOB technology. In this paper, an accelerated environmental testing HAST-was used to rapidly evaluate the reliability of area array solder bumped packages on FR-4 PCBs. The test results intend to identify the effective reliability test criteria for low-cost FCOB technology.

This paper appears in: Electronic Packaging Technology Proceedings, 2003. ICEPT 2003. Fifth International Conference on vol., no., pp. 386-388, 28-30 Oct. 2003