Cook Your Chips and PCBs

-May 01, 1999


Read the T&MW Product Survey of Environmental Test Chambers.

This article also ran in Test & Measurement Europe. Read the PDF Version Here.
A variety of thermal environmental-test products can help you test electronic devices and subassemblies and subject them to temperature extremes. They range from benchtop hot plates to walk-in chambers. In between, you’ll find a plethora of ovens, conductive coolers and heaters, and forced-air sources. (See our product survey, below)
Burn-in is the traditional form of environmental test, in which you subject devices to their rated voltages and temperatures either before or during production test to weed out devices that would quickly fail in the field. An alternative to burn-in—a process that can take hours—is environmental stress screening (ESS), a process that seeks to hasten infant mortalities by rapidly cycling devices under test through high and low temperature extremes while subjecting them to high supply voltages and—optionally—vibration.(1)
Figure 1. You don’t necessarily need an environmental chamber to test your product’s temperature performance. For example, this Model TP04100A ThermoStream system from Temptronic can focus 2 to 6 SCFM of heated or cooled air on a DUT.

If you intend to cycle your devices through hot and cold extremes you’ll need a chamber that cools and heats. If your cooling requirements are modest, you can employ a closed mechanical refrigeration unit or a water-cooled system. For lower temperatures you’ll need to supply liquid CO2 to provide cooling down to –65°C. Below that, you’ll need liquid nitrogen (LN2).

Lab and Bench Test
For thermal testing in the lab you have several choices. If your product uses a heat sink for direct-conduction cooling, you can employ a benchtop thermal platform—a hot (or cold) plate onto which you can clamp your product’s heat sink. Environmental Stress Systems (ESS) makes such products; the company’s T600 Series thermal platforms cover a –65°C (LCO2) or –100°C (LN2) to +200°C range and offer 2x2-in. to 11x22-in. plate areas.

If your product must be convection cooled, you can select a benchtop temperature chamber. An alternative is a benchtop conditioned-air source such as Temptronic’s Model TP04100A ThermoStream system ( Fig. 1), which can focus 2 to 6 SCFM (cubic feet per minute at standard room temperature, pressure, and humidity) of heated or cooled air onto a device under test.

Production Burn-in
For thermal evaluation of production devices, you can choose from a variety of floor-standing environmental chambers, such as the one in Figure 2. Or you can use a temperature forcing system to deliver conditioned air to your ATE test site.
Figure 2. (a) A touch-screen panel mounted at eye level helps users control Tenney’s line of environmental chambers. (b) A floppy-disk drive provides for storage of temperature-control information.

Depending on your manufacturing setup and on what equipment you already own, you might choose a system that provides thermal-control capabilities as well as other functions, such as pick-and-place device handling (Fig. 3).

To control the burn-in temperatures of production devices, you will probably need a combination of the hot-plate and chamber approaches. The factory-floor analog of the lab hot plate is a clamshell arrangement that brings a conductive heat sink or source into contact with each device on a burn-in board. If your product doesn’t lend itself to conductive heating and cooling, you can choose a simple oven to convectively apply thermal stress to your devices before testing them. Going a step further, you can cycle the devices through thermal extremes at programmable rates of temperature change. The limit of such testing is the thermal shock test, in which your product plunges nearly instantaneously from a hot thermal chamber to a cold one, or vice versa.

Don’t overlook the need for cooling even if your application calls only for burn-in. If you’re burning-in multiple VLSI devices at once with power applied, you’ll find they often generate more than enough heat to keep your burn-in chamber at rated temperature, and the challenge will be to safely channel away the excess heat.

For best results, you’ll want to electrically test your devices while subjecting them to environmental test (see "Control Chip Temperature During VLSI Device Burn-in," Test & Measurement World, April 1999, p. 67). That complicates matters. You have to choose a system that not only meets your environmental requirements but also includes—or is compatible with—the necessary instrumentation. In addition, your temperature control is complicated, because the controller must contend with various levels of device heat dissipation in response to varying input test patterns.
Figure 3. Many vendors combine environmental-test capabilities with other functions. For instance, this pick-and-place memory handler from Delta Design can condition devices at temperatures from –60°C to +160°C. It handles such surface-mount chip packages as TSOP, BGA, mBGA, QPF, and PLCC.

Temptronic doesn’t provide instrumentation. For its ThermoFixture thermal-inducing enclosure, however, it does offer interfaces to ATE from many companies.

Accurate Temperature Control
Precise thermal control and fast thermal response are critical in today’s test environments. Accuracy is paramount if you are characterizing temperature-sensitive components such as crystal oscillators. For such applications, you can employ systems such as Saunders & Associates’ temperature test systems, designed to characterize crystals, capacitors, diodes, resistors, and ECL, TTL, CMOS, and HMOS oscillators. These systems comprise temperature chambers as well as instrumentation. Temperature accuracy is ±0.1°C.

If you’re burning-in VLSI devices you won’t need ±0.1°C accuracy. Accuracy is nevertheless important, especially when testing high-density chip-scale packaging technologies.(2) For example, the low thermal mass of a flip-chip or C4 package can result in the device quickly reaching destructive temperatures in response to changes in dissipation due to varying input test patterns. Schlumberger has addressed this issue with its ETC 1000 (Fig. 5), a thermal controller that can maintain DUT package temperatures to within ±0.1°C.

Bake, Shake, and Sweat
A combination of thermal cycling while applying other stresses (such as vibration, altitude, and humidity) can expedite your environmental test. This ESS approach can accelerate the infant mortalities that might appear only after hours of burn-in. Moreover, by realistically simulating your product’s target environment, you can verify that your product is up to its intended task.
Figure 4. Simultaneous burn-in and test can help verify that your devices will operate properly at temperature extremes. Integral 75-MHz JTAG signal generation enables the ScanPro from Unisys Unigen to burn-in JTAG devices while testing them.

Two other ESS implementations are highly accelerated lift test and highly accelerated stress screening, developed by Qualmark founder Gregg K. Hobbs. HALT and HASS both combine thermal and vibration stress. HALT is a destructive test used to estimate the potential lifetime of a product under development; HASS is a nondestructive test used to qualify production devices.

More Stress Sooner
The future is likely to see environmental testing earlier in the production process. Burn-in at the die and wafer level are two approaches being pursued; these approaches avoid the expense of packaging dice that would fail during a traditional package burn-in process.

 

 

Figure 5. Careful control of semiconductor temperatures operating near device thermal limits is critical to ensuring an adequate test while not destroying the device. Schlumberger’s ETC 1000 can deliver 22 SCFM of air to an ATE test head to maintain a temperature of -35°C to +125°C (±1°C) at the device under test’s heat spreader or C4-package substrateFigure 5. Careful control of semiconductor temperatures operating near device thermal limits is critical to ensuring an adequate test while not destroying the device. Schlumberger’s ETC 1000 can deliver 22 SCFM of air to an ATE test head to maintain a temperature of -35°C to +125°C (±1°C) at the device under test’s heat spreader or C4-package substrate

In addition to employing environmental test early in production, efforts are underway to shorten burn-in and ESS times. One approach is to subject devices to high temperatures and overvoltages (for instance, 8.5 V on a 5-V part) for a matter of milliseconds instead of rated voltage for a matter of hours. This technique, called accelerated dynamic burn-in (ADBI), shows promise for detecting weak parts when combined with IDDQ testing.3 Though not yet ready for prime time, ADBI shows promise as efforts proceed to provide maximum reliability in minimum time. T&MW

FOOTNOTES
1. Kececioglu, Dimitri B., and Feng-Bin Sun, Environmental Stress Screening, Prentice-Hall, Upper Saddle River, NJ, 1995, ISBN 0-13-324229-3.
2. Malinoski, Mark, et. al., "A Test Site Thermal Control System for At-Speed Manufacturing Testing," Proceedings, International Test Conference 1998, Washington, DC, pp. 119-128, www.itctestweek.org
3. Dudinski, Frank E., "Why Burn-in and Is It Necessary?" Yamaichi Electronics USA, San Jose, CA, www.yeu.com/banner3.html

FOR FURTHER READING
Izumi, Jyuro, "Combined environmental testing for equipment used on automobiles," Technology Report No. 6, September 30, 1998, pp. 9–17, Tabai Espec Corp., Osaka, Japan, www.espec.com/features/tech_report.htm  

T&MW
Product Survey: Environmental Test Chambers
Aehr Test Systems
Mountain View, CA
650-691-9400
www.aehr.com
Test with Burn-in, Memory, Digital, Temperature Chambers, Hot Only, Hot/ColdAetrium
North St. Paul, MN
651-704-1800
Mixed Signal, Temperature Chambers, Temperature and Vibration, Environmental Stress
Ando
San Jose, CA
408-941-0110
www.ando.com
Test with Burn-in, Memory
Associated Environmental Systems
Ayer, MA
978-772-0022
www.associatedonline.com
Temperature Chambers, Walk-in Chambers, Benchtop, Hot Only, Hot/Cold, Hot/Cold/Humidity, Environmental Stress, Thermal Cycling, Thermal Shock.
Blue M Electric
Watertown, WI
800-216-7725
www.blue-m.com
Walk-in Chambers, Benchtop,  Hot/Cold, Hot/Cold/Humidity, Temperature and Altitude, Thermal Cycling, Thermal Shock, Temperature Platforms.

BMA
Ayer, MA
888-772-3310
www.testchamber.com
Temperature Chambers, Walk-in Chambers, Hot Only, Hot/Cold, Hot/Cold/Humidity, Environmental Stress, Thermal Cycling, Thermal Shock
Cincinnati Sub-Zero
Cincinnati, OH
513-772-8810
www.cszinc.com
Temperature Chambers, Walk-in Chambers, Hot Only, Hot/Cold, Hot/Cold/Humidity, Temperature and Altitude, Temperature and Vibration, Environmental Stress, Thermal Cycling, Thermal Shock.
Delta Design
San Diego, CA
619-292-5000
www.cohu.com/delta.htm
Test with Burn-in, Memory, Digital, Mixed Signal, Temperature Chambers, Walk-in Chambers.
Despatch Industries
Minneapolis, MN
800-860-3944
www.despatch.com
Mixed Signal, Temperature Chambers, Benchtop, Hot Only, Temperature and Vibration, Environmental Stress.
Environmental Stress Systems
Sonora, CA
209-588-1993
www.essproducts.com
Temperature Chambers, Walk-in Chambers, Benchtop, Hot Only, Hot/Cold, Temperature and Altitude, Temperature and Vibration, Thermal Cycling, Temperature Platforms.
Envirotronics
Grand Rapids, MI
616-554-5020
www.envirotronics.com
Temperature Chambers, Walk-in Chambers, Hot Only, Hot/Cold, Hot/Cold/Humidity,   Temperature and Vibration, Environmental Stress, Thermal Cycling, Thermal Shock.
ESPEC
Grand Rapids, MI
616-878-0270
www.espec.com
Temperature Chambers, Walk-in Chambers, Benchtop, Hot Only, Hot/Cold, Hot/Cold/Humidity, Environmental Stress, Thermal Cycling, Thermal Shock.
FTS Systems
Stone Ridge, NY
800-824-0400
www.ftssystems.com
Environmental Stress, Thermal Cycling.
Hotpack
Philadelphia, PA
800-523-3608
www.hotpack.com
Temperature Chambers, Walk-in Chambers, Benchtop, Hot Only, Hot/Cold, Hot/Cold/Humidity, Environmental Stress, Thermal Cycling.
Micro Control Co.
Minneapolis, MN
612-786-8750
www.microcontrol.com
Test with Burn-in, Memory, Digital, Temperature Chambers, Walk-in Chambers, Hot Only, Hot/Cold, Environmental Stress, Thermal Cycling.
Parameter Generation and Control
Black Mountain, NC
800-438-5494
www.humiditycontrol.com
Temperature Chambers, Walk-in Chambers, Hot/Cold, Hot/Cold/Humidity.
QualMark
Denver, CO
303-254-8800
www.qualmark.com
Temperature Chambers, Walk-in Chambers, Hot Only, Hot/Cold, Temperature and Vibration, Environmental Stress, Thermal Cycling, Thermal Shock.
Ransco Industries
Oxnard, CA
805-487-7777
www.ransco.com
Temperature Chambers, Walk-in Chambers, Hot/Cold, Environmental Stress, Thermal Cycling.

Saunders & Associates
Scottsdale, AZ
480-991-9250
www.saunders-assoc.com
Temperature Chambers, Hot Only, Hot/Cold.
Schlumberger
San Jose, CA
408-453-0123
www.slb.com/ate
Test with Burn-in, Memory, Digital, Mixed Signal.
Scientific Climate Systems
Houston, TX
713-781-6447
www.scs-usa.com
Temperature Chambers, Walk-in Chambers, Hot Only, Hot/Cold, Environmental Stress, Thermal Cycling, Thermal Shock.Screening Systems
Laguna Hills, CA
949-855-1751
www.scrsys.com
Mixed Signal, Temperature Chambers, Temperature and Altitude.
Sigma Systems
San Diego, CA
619-283-3193
www.sigmasystems.com
Temperature Chambers, Walk-in Chambers, Benchtop, Hot Only, Hot/Cold, Hot/Cold/Humidity, Temperature and Vibration, Environmental Stress, Thermal Cycling, Thermal Shock, Temperature Platforms.

Sun Electronic Systems
Titusville, FL
407-383-9400
www.sunelectronics.com
Temperature Chambers, Walk-in Chambers, Benchtop, Hot/Cold, Environmental Stress, Thermal Shock.
Temptronic
Newton, MA
617-969-2501
www.temptronic.com
Test with Burn-in (via turn-key interface to ATE), Temperature Chambers, Benchtop.
Tenney Environmental
Williamsport, PA
717-326-1770
www.tenneyenv.com
Temperature Chambers, Walk-in Chambers, Benchtop, Hot Only, Hot/Cold, Hot/Cold/Humidity, Temperature and Altitude, Environmental Stress, Thermal Cycling, Thermal Shock.
Thermonics
Santa Clara, CA
408-496-6838
www.thermonics.com
Environmental Stress, Thermal Cycling, Thermal Shock.
Thermotron Industries
Holland, MI
616-392-1491
www.thermotron.com
Test with Burn-in (via card cage mountable in thermal chamber), Temperature Chambers, Benchtop, Hot Only, Hot/Cold/Humidity, Temperature and Altitude, Temperature and Vibration, Environmental Stress, Thermal Cycling, Thermal Shock.
Unisys Unigen
Chandler, AZ
602-961-0654
www.motay.com 
Test with Burn-in, Memory, Digital, Mixed Signal, Temperature Chambers, Hot/Cold.

Weiss Environmental Technology
Menomonee Falls, WI 414-253-8730;
www.macataw/~weiss
Temperature Chambers, Walk-in Chambers, Hot Only, Hot/Cold, Hot/Cold/Humidity, Temperature and Vibration, Environmental Stress, Thermal Cycling.

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