AEHR TEST SYSTEMS Value Stock - Dividend - Research Selection

Aehr Test was incorporated in the state of California on May 25, 1977. We develop, manufacture and sell systems which are designed to reduce the cost of testing and to perform reliability screening, or burn-in, of complex logic devices, memory ICs, sensors and optical devices. These systems can be used to simultaneously perform parallel testing and burn-in of packaged integrated circuits, or ICs, singulated bare die or ICs still in wafer form. Increased quality and reliability needs of the Automotive, Mobility and flash memory integrated circuit markets are driving additional testing requirements, capacity needs and opportunities for Aehr Test products in package and wafer level testing. Leveraging its expertise as a long-time leading provider of burn-in equipment, with over 2,500 systems installed worldwide, the Company has developed and introduced several innovative product families, including the ABTSTM and FOXTM systems, the WaferPakTM cartridge and the DiePak® carrier. The latest ABTS family of packaged part burn-in and test systems can perform test during burn-in of complex devices, such as digital signal processors, microprocessors, microcontrollers and systems-on-a-chip, and offers individual temperature control for high-power advanced logic devices. The FOX systems are full wafer contact parallel test and burn-in systems designed to make contact with all pads of a wafer simultaneously, thus enabling full wafer parallel test and burn-in. The WaferPak cartridge includes a full-wafer probe card for use in testing wafers in FOX systems. The DiePak carrier is a reusable, temporary package that enables IC manufacturers to perform cost-effective final test and burn-in of singulated bare die or very small multi-IC modules.

INDUSTRY BACKGROUND

Semiconductor manufacturing is a complex, multi-step process, and defects or weaknesses that may result in the failure of an integrated circuit, or IC, may be introduced at any process step. Failures may occur immediately or at any time during the operating life of an IC, sometimes after several months of normal use. Semiconductor manufacturers rely on testing and reliability screening to identify and eliminate defects that occur during the manufacturing process.

Testing and reliability screening involve multiple steps. The first set of tests is typically performed by IC manufacturers before the processed semiconductor wafer is cut into individual die, in order to avoid the cost of packaging defective die into their packages. This “wafer probe” testing can be performed on one or many die at a time, including testing the entire wafer at once. After the die are packaged and before they undergo reliability screening, a short test is typically performed to detect packaging defects. Most leading-edge microprocessors, microcontrollers, digital signal processors, memory ICs, sensors and optical devices (such as vertical-cavity surface-emitting lasers, or VCSELs) then undergo an extensive reliability screening and stress testing procedure known as “burn-in” or “cycling,” depending on the application. The burn-in process screens for early failures by operating the IC at elevated voltages and temperatures, up to 150 degrees Celsius (302 degrees Fahrenheit), for periods typically ranging from 2 to 48 hours. A typical burn-in system can process thousands of ICs simultaneously. After burn-in, the ICs undergo a final test process using automatic test equipment, or testers. The cycling process screens flash memory devices for failure to meet write/erase cycling endurance requirements.

PRODUCTS

The Company manufactures and markets full wafer contact test systems, test during burn-in systems, test fixtures, die carriers and related accessories.

All of the Company’s systems are modular, allowing them to be configured with optional features to meet customer requirements. Systems can be configured for use in production applications, where capacity, throughput and price are most important, or for reliability engineering and quality assurance applications, where performance and flexibility, such as extended temperature ranges, are essential.

FULL WAFER CONTACT SYSTEMS

The FOX-1P full wafer parallel test system, introduced in October 2014, is designed for massively parallel test of devices at wafer level. The FOX-1P system is designed to make electrical contact to and test all of the die on a wafer in a single touchdown. The FOX-1P test head and WaferPak contactor are compatible with industry-standard 300 mm wafer probers which provide the wafer handling and alignment automation for the FOX-1P system. The FOX-1P pattern generator is designed to functionally test industry-standard memory devices such as flash and DRAMs, plus it is optimized to test memory or logic ICs that incorporate design for testability, or DFT, and built-in self-test, or BIST. The FOX-1P universal per-pin architecture to provide per-pin electronics and per-device power supplies is tailored to full-wafer functional test. The Company believes that the FOX-1P system can significantly reduce the cost of testing IC wafers. The Company’s FOX-1P system was partially funded through a development agreement with a leading semiconductor manufacturer. The Company has received the first production order of this new system and shipped the first system in July 2016.

The FOX-XP test and burn-in system, introduced in July 2016, is designed for devices in wafer, singulated die, and module form that require test and burn-in times typically measured in hours. The FOX-XP system can test and burn in up to 18 wafers at a time. For high reliability applications, such as automotive, mobile devices, sensors, and SSDs, the FOX-XP system is a cost-effective solution for producing tested and burned-in die for use in multi-chip packages. Using Known-Good Die, or KGD, which are fully burned-in and tested die, in multi-chip packages helps assure the reliability of the final product and lowers costs by increasing the yield of high-cost multi-chip packages. Wafer-level burn-in and test enables lower cost production of KGD for multi-chip modules, 3-D stacked packages and systems-in-a-package. The FOX-XP system has been extended for burn-in and test of small multi-die modules by using DiePak carriers. The DiePak carrier with its multi-module sockets and high wattage dissipation capabilities has a capacity of hundreds of modules, much higher than the capacity of a traditional burn-in system with traditional single-die sockets and heat sinks. This capability was introduced in March 2017.

The FOX-15 full wafer parallel test system, the predecessor to the FOX-XP system, was introduced in October 2007 and was designed for full-wafer test and burn-in. The FOX-15 system is nearing the end of its lifecycle and limited shipments are expected in the future.

One of the key components of the FOX systems is the patented WaferPak cartridge system. The WaferPak cartridge contains a full-wafer single-touchdown probe card which is easily removable from the system. Traditional probe cards contact only a portion of the wafer, requiring multiple touchdowns to test the entire wafer. The unique design is intended to accommodate a wide range of contactor technologies so that the contactor technology can evolve along with the changing requirements of the customer’s wafers. The WaferPak cartridges are custom designed for each device type, each of which has a typical lifetime of 2 to 7 years, depending on the application. Therefore, multiple sets of WaferPak cartridges could be purchased over the life of a FOX system.

A key new component of the FOX-XP systems is the patent-pending DiePak carrier system. The DiePak carrier contains many multi-module sockets with very fine-pitch probes which are easily removable from the system. Traditional sockets contact only a single device, requiring multiple large numbers of sockets and burn-in boards to test a production lot of devices. The unique design is intended to accommodate a wide range of socket sizes and densities so that the DiePak carrier technology can evolve along with the changing requirements of the customer’s devices. The DiePak carriers are custom designed for each device type, each of which has a typical lifetime of 2 to 7, years depending on the application. Therefore, multiple sets of DiePak carriers could be purchased over the life of a FOX-XP system.

Another key component of our FOX-XP and FOX-15 test cell is the WaferPak Aligner. The WaferPak Aligner performs automatic alignment of the customer’s wafer to the WaferPak cartridge so that the wafer can be tested and burned-in by the FOX-XP and FOX-15 systems. Typically one WaferPak Aligner can support several FOX-XP or FOX-15 systems.

Similar to the WaferPak Aligner for WaferPak cartridges, Aehr Test offers a DiePak Loader for DiePak carriers. The DiePak Loader performs automatic loading of the customer’s modules to the DiePak carrier so that the modules can be tested and burned-in by the FOX-XP system. Typically one DiePak Loader can support several FOX-XP systems.

The full wafer contact systems product category accounted for approximately 51%, 60% and 31% of the Company’s net sales in fiscal 2017, 2016 and 2015, respectively.

SYSTEMS FOR PACKAGED PARTS

Test during burn-in, or TDBI, systems consist of several subsystems: pattern generation and test electronics, control software, network interface and environmental chamber. The test pattern generator allows duplication of most of the functional tests performed by a traditional tester. Pin electronics at each burn-in board, or BIB, position are designed to provide accurate signals to the ICs being tested and detect whether a device is failing the test.

Devices being tested are placed on BIBs and loaded into environmental chambers which typically operate at temperatures from 25 degrees Celsius (77 degrees Fahrenheit) up to 150 degrees Celsius (302 degrees Fahrenheit) (optional chambers can produce temperatures as low as -55 degrees Celsius (-67 degrees Fahrenheit)). A single BIB can hold up to several hundred ICs, and a production chamber holds up to 72 BIBs, resulting in thousands of memory or logic devices being tested in a single system.

The Advanced Burn-in and Test System, or ABTS, was introduced in fiscal 2008. The ABTS family of products is based on a completely new hardware and software architecture that is intended to address not only today’s devices, but also future devices for many years to come. The ABTS system can test and burn-in both high-power logic and low-power ICs. It can be configured to provide individual device temperature control for devices up to 70W or more and with up to 320 I/O channels.

The MAX system family, the predecessor to the ABTS family, was designed for monitored burn-in of memory and logic devices. The MAX system is nearing the end of its lifecycle and limited shipments are expected in the future.

This packaged part systems product category accounted for approximately 49%, 40% and 65% of the Company’s net sales in fiscal 2017, 2016 and 2015, respectively.

TEST FIXTURES

The Company sells, and licenses others to manufacture and sell, custom-designed test fixtures for its systems. The test fixtures include BIBs for the ABTS parallel test and burn-in system and for the MAX monitored burn-in system. These test fixtures hold the devices undergoing test or burn-in and electrically connect the devices under test to the system electronics. The capacity of each test fixture depends on the type of device being tested or burned-in, ranging from several hundred in memory production to as few as eight for high pin-count complex Application Specific Integrated Circuits, or ASICs, or microprocessor devices. Test fixtures are sold both with new Aehr Test systems and for use with the Company’s installed base of systems. Test fixtures are also available from third-party suppliers.

The Company’s single and multi-die DiePak product line includes a family of reusable, temporary die carriers and associated sockets that enable the test and burn-in of bare die and modules. The singulated die DiePak carriers offer cost-effective solutions for providing KGD for most types of ICs, including memory, microcontroller and microprocessor devices. The DiePak carrier consists of an interconnect substrate, which provides an electrical connection between the die pads and the socket contacts, and a mechanical support system. The substrate is customized for each IC product. The single and multi-die DiePak carriers come in several different versions, designed to handle ICs ranging from low pin count sensors, to high pin count microprocessors.

The Company has received patents or applied for patents on certain features of the FOX, ABTS and MAX4 test fixtures. The Company has licensed or authorized several other companies to provide MAX4 BIBs from which the Company receives royalties. Royalties and revenue for the test fixtures product category accounted for less than 5% of net sales in fiscal 2017, 2016 and 2015.