HALT experiment and HASS experiment in reliability test
Ningbo DOKEE Medical Technology Co., Ltd. , https://www.dokeemedical.com HALT experiment and HASS experiment in reliability test
HALT test and HASS test in reliability test HALT HASS is a test method for design quality verification and manufacturing quality verification extended by the US military. It has become the standard product verification method in the US electronics industry. It shortened the reliability test of new products that took 6 months or even 1 year to a week, and the product problems found during this week were almost the same as customer applications.
HALT experiment and HASS experiment in reliability test
HALT & HASS is a test method for design quality verification and manufacturing quality verification extended by the US military. It has become the standard product verification method for the US electronics industry. It shortened the reliability test of new products that took 6 months or even 1 year to one week, and the product problems found during this week were almost the same as those found after the customer applied, so the HALT & HASS test method has been Be sure to pass the verification before the new product goes on the market. Outside the United States, many international 3C electronics manufacturers use the same or similar methods to improve product quality.
1, HALT
HALT is an experimental method that allows the measured object to withstand different stresses, and then finds its design flaws and potential weaknesses. The main purpose of HALT is to increase the robustness and reliability of the measured object by increasing the limit value of the measured object. HALT is applied to products by means of step stress, and can detect product defects, operational design margins, and structural strength limits at an early stage. . The stresses imposed on the product include vibration, high and low temperature, temperature cycling, power switching cycle, voltage margin and frequency margin test. This test can quickly identify product design and manufacturing defects, improve design defects, increase product reliability and shorten its time to market, and also establish basic data for design capabilities, product reliability, and important basis for future R&D.
Simply put, HALT consists of continuous testing, analysis, verification, and correction to form the entire process. The key is to analyze the root cause of all failures.
The main test functions of HALT are as follows:
Use high environmental stress to inspire product design flaws and improve them;
Understand the design capabilities and failure modes of the product;
As a reference for high stress screening and audit specification development;
Quickly identify the flaws in the manufacturing process of the product;
Increase product reliability and reduce maintenance costs;
Establish a product design capability database to provide a basis for research and development and shorten the design and manufacturing cycle.
HALT is used in the product development phase to detect weaknesses in product reliability early. The stress applied is much higher than the stress of the product during normal transportation, storage and use.
HALT contains the following:
Apply stress gradually until the product fails or fails;
Take temporary measures to correct the failure or malfunction of the product;
Continue to apply stress gradually until the product fails again or fails and is corrected again;
Repeat the above stress-fail-correction steps;
Find the basic operating limits and basic damage boundaries of the product.
2, HASS
HASS is used in the production phase of the product to ensure that all improvements found in HALT can be implemented. HASS also ensures that new defects are not introduced due to changes in production processes and components.
HASS contains the following:
Perform pre-screening to remove hidden defects that may develop into obvious defects;
Perform detection and screening to identify obvious defects;
Failure analysis
improvement measures.
HALT & HASS reliability test steps
1, HALT
HALT is divided into 4 main tests, namely:
Temperature stress
High speed temperature conduction;
Random vibration
Temperature and vibration combined with stress.
In the HALT test, the operable limits and damage limits of the measured object under temperature and vibration stress can be found. The equipment used in this experiment is the OVS Combined Stress System designed by QualMark. The temperature range is from -100 °C to +200 °C, the temperature change zui is 60 °C/min, and the Zui acceleration is 60 Grms. Moreover, the combination of the vibrating machine and the temperature box can simultaneously apply temperature and vibration stress to the measured object. The following is a general description of the four test procedures:
(1) Temperature stress (HL high and low temperature test chamber)
This test is divided into two stages of low temperature and high temperature stress. Firstly, the low temperature stress is set, the initial temperature is set to 20 ° C, the temperature is lowered by 10 ° C per stage, and the temperature is maintained for 10 min after the stage temperature is stabilized. Then, at least one functional test is performed at the steady temperature of the stage. If everything is normal, the temperature is lowered again by 10 °C, and wait for the temperature to stabilize for 10 minutes before performing the function, and so on until the functional failure occurs to determine whether the operating limit or the damage limit is reached; after the low temperature stress test is completed, the high temperature stress test can be performed according to the same procedure, that is, the comprehensive environment The stress tester starts at 20 ° C, and the temperature is raised by 10 ° C per stage. After the temperature is stabilized, it is maintained for 10 min, and then the functional test is performed until the high temperature operation limit and the high temperature failure limit are found.
(2) High-speed temperature conduction
This test uses the low temperature and high temperature control limits previously obtained in the temperature phase stress test as the high and low temperature limits here, and performs 6 cycles of high and low temperature changes in this interval at a rapid temperature change rate of 60 ° C per minute. . In each cycle, the high temperature of zui and the low temperature of zui are kept for 10 minutes, and the temperature is stabilized before performing the functional test. Check the test object for recoverable faults and find the operational limits. There is no need to find the boundaries of damage in this test.
(3) Random vibration (Ai Siwei vibration testing machine)
In this test, the G value is started from 5g, and each stage is increased by 5g, and after each stage is maintained for 10min, the functional test is performed under the condition of continuous vibration to judge whether it reaches the operable limit or the damage limit.
(4) Temperature and vibration combined stress (ASLI temperature and humidity vibration three comprehensive testing machine)
This test combines high-speed temperature conduction and random vibration testing simultaneously, making the effect of accelerated aging more significant. Here, the previous rapid temperature change cycle conditions and temperature change rate are used, and the random vibration is incremented by 5g from 5g per cycle, and the zui high and zui low temperature of each cycle are continued for 10min, and the function is performed after the temperature is stabilized. The test is repeated as described above until the operational limit and the damage limit are reached.
Record any abnormal conditions generated by the test object in the above four test procedures, analyze whether the problem can be overcome by changing the design, and then modify the test to the next step. Improve reliability by increasing the operational limits and breaking boundaries of the product.
2, HASS
The purpose of applying HASS is to find out whether there is a production quality hazard in the mass production of finished products in a very short period of time. The test consists of three main tests:
HASS Development (HASS test plan phase);
Proof-of-Screen (plan verification phase);
Production HASS (HASS execution phase).
The following describes the testing process for general electronic products:
(1) HASS Development
The HASS test plan must refer to the results obtained from the previous HALT test. Generally, the operational limit of high and low temperatures in the temperature and vibration combined stress is reduced by 20%, and the vibration condition is 50% of the G value of the damage limit as the initial condition of the HASS test plan. Then start the temperature and vibration combined stress test according to this condition, and observe whether the measured object has a fault. If a fault occurs, it must be judged whether it is caused by excessive environmental stress or by the mass of the measured object itself. When it belongs to the former, it should relax the temperature and vibration stress by 10% and then test it. In the latter case, the current test conditions are valid. If no fault occurs, the environmental stress must be further tested by 10% before testing.
(2) Proof-of-Screen
There are two principles to be aware of when establishing a HASS Profile: First, you must be able to detect potential hazards that may cause equipment failure. Second, it will not cause equipment damage or "injury" after testing. In order to ensure that the results obtained during the HASS test planning phase meet the above two principles, three test articles must be prepared, and defects on those samples that are not manufactured or assembled according to standard processes, such as parts floating and empty welding, and Improper assembly, etc. Test each test article under the conditions obtained during the HASS test plan phase, and observe whether the artificial defects on each test sample can be detected to determine whether the test conditions are tightened or relaxed, and the HASS Profile can achieve the desired effect.
After the validity test is completed, the new test article should be tested 30 to 50 times with the adjusted conditions. If no damage occurs due to improper stress, the HASS Profile can be judged through the plan verification stage. Tested and used as Production HASS. Otherwise, it is necessary to review and adjust the test conditions in order to obtain a good combination of Zui.
(3) Production HASS
Any HASS Profile that has been tested by Proof-of-Screen is considered a fast and effective quality screening tool, but it must be adjusted to match the abnormality of the product after the customer has used it. In addition, when the design changes, the test conditions are modified accordingly.