A reliability test that keeps products at high temperature without applying voltage to evaluate degradation of wire-bond joints, data retention in nonvolatile memory and similar effects. It is also called HTS or HTSL.
Japanese name: 高温放置試験(高温保存試験)
High-temperature storage test (HTS) appears in 1 practice question across 1 topic, including Reliability.
Field: Reliability
The high-temperature storage test places products in an oven at high temperature without applying voltage and compares their electrical characteristics before, during and after the test. It is also called high temperature storage (HTS) or high temperature storage life (HTSL). In JEDEC standards (the JESD22 series) and elsewhere, 1000 hours at 150 °C, for example, is a typical condition, and some products or standards use higher temperatures for shorter times. Because no voltage or signals are applied, the equipment is simple, many samples can be tested at once, and degradation driven by temperature alone can be isolated.
A typical target is the wire-bond joint. Where a gold wire meets an aluminum pad, gold-aluminum intermetallic compounds grow at high temperature, and when the difference in diffusion rates creates voids (Kirkendall voids), the joint's resistance rises or the bond lifts. For copper wire bonds, intermetallic growth and corrosion are also important to evaluate. High-temperature storage is further used to evaluate thermal degradation of materials such as mold compound and die-attach material, as well as data retention in nonvolatile memory.
HTOL (high-temperature operating life test) operates parts at high temperature under voltage, so it also accelerates degradation driven by electric field or current, such as TDDB and electromigration. The high-temperature storage test applies no voltage, so it cannot evaluate those mechanisms, but in exchange it can single out degradation caused by temperature alone. The temperature-humidity-bias test (THB) accelerates corrosion with humidity and voltage, and temperature cycling applies strain from temperature changes. Because each targets different failures, qualification combines them. The storage temperature range in a datasheet specifies where parts may be stored and is separate from test conditions.
In flash memory and EEPROM, charge stored on a floating gate or in a charge-trap film leaks out faster at higher temperature. Products with data written are therefore stored at high temperature to check that they still read correctly after a specified time. Because repeated rewriting degrades the dielectrics and makes charge loss easier, a common approach is to wear the parts first with an endurance test and then bake them. Results are converted to retention time at use temperature with the Arrhenius model, using an activation energy assumed for the failure mechanism, but the assumption can change the result greatly.
Answer: C. Electrical bias such as supply voltage
The high-temperature storage test (HTS) holds products at high temperature, for example around 150 °C, for a long time without applying voltage and compares their electrical characteristics before and after. HTOL operates products at high temperature under supply voltage, so it also accelerates degradation driven by electric field or current, such as TDDB and electromigration, whereas the high-temperature storage test isolates degradation driven by temperature alone. Typical targets are intermetallic growth and voiding at wire-bond joints, which raise resistance or cause the bond to lift, data retention in nonvolatile memory, and degradation of materials such as mold compound. The test that applies humidity and voltage together is the temperature-humidity-bias test (THB).
A high-temperature storage test only holds parts at high temperature without voltage, evaluating degradation driven by temperature alone. HTOL operates parts at high temperature under voltage, so it also accelerates degradation driven by electric field and current.
1000 hours at 150 °C, for example, is a typical condition. Actual temperature and time depend on the applicable standard, the package materials and the product's temperature grade, and higher temperatures with shorter times are sometimes used.
They include HTOL, which operates parts under temperature and voltage; the high-temperature storage test, which applies temperature only; temperature-humidity-bias testing (THB) and HAST, which apply temperature, humidity and voltage; and temperature cycling, which repeats temperature changes. Each intensifies the stresses that cause failures so that lifetime and failure rate can be evaluated in a short time.
The high-temperature storage test (HTS) holds products at high temperature, for example around 150 °C, for a long time without applying voltage and compares their electrical characteristics before and after.
Which stress is applied in HTOL but not in a high-temperatu…As an Amazon Associate I earn from qualifying purchases.
HTOL (high-temperature operating life test) TDDB (time-dependent dielectric breakdown) Electromigration Nonvolatile memory THB (temperature-humidity-bias test) Arrhenius model Bathtub curve ESD (electrostatic discharge) FIT rate Hot carrier injection (HCI)