Burn-In and Environmental Stress Screening

Burn-in runs production units powered, at elevated temperature, for a defined period, so that units carrying a latent manufacturing defect fail here instead of at your customer. Environmental stress screening does the same job with a profile that adds thermal cycling, and sometimes vibration, to precipitate defects faster. Megalab runs both to your production specification, in chambers accredited to ISO/IEC 17025 by A2LA from -68 C to 180 C, with humidity up to 98 % RH at temperatures above 15 C.

A functional test at the end of a line asks whether the unit works now. Most manufacturing defects pass it. A cold solder joint conducts, a partially seated connector mates, a cracked component still meets spec, a marginal wire bond holds. They fail later, in the field, inside the warranty period, at a rate that looks random because nothing on the line distinguished them from good units.

Screening applies stress that good units absorb without meaningful damage and defective units do not survive. The infant-mortality population fails in the chamber. What ships is the flat part of the curve.

The economics are the argument. A unit that fails on your floor costs a rework. The same unit failing at a customer costs a truck roll, a replacement, the investigation, and the part of your reputation that does not show up on an invoice. For anything shipped in volume, or anything whose field replacement cost dwarfs its unit cost, screening pays for itself long before the failure rate does.

• Burn-in is a steady, extended, powered dwell at elevated temperature. It is the classic semiconductor and electronics screen, and it is what most customer specifications mean by the word. Duration is set by your specification, not by us.
• Environmental stress screening adds movement. A typical ESS profile cycles temperature rather than holding it, because the rate of change precipitates defects far faster than a soak at the same temperature, and some profiles add random vibration on top. ESS gets the same defects out in less chamber time, at the cost of a more complex setup.
• HASS is ESS with its levels derived from a measured destruct limit rather than from a standard, and that measurement comes from a HALT. If you have not run one, ESS to a specification is the right starting point. If you have, see HALT and HASS.

Burn-in and environmental stress screening run in our ISO/IEC 17025 accredited laboratory on accredited, calibrated instrumentation. The accreditation extends to customer supplied and industry specifications built on the same technologies, so when your production specification defines the screen, the chamber work is performed and reported under it. See our accreditations.

Units arrive with your specification, your power and load arrangement, and your pass criteria. We fixture them, feed power and monitoring through the chamber ports, run the profile, and record which units failed and when.

The practical constraint on any screen is chamber time multiplied by unit count, which is why chamber size matters more here than on a one-off qualification. Our reach-in chambers suit board and module quantities. For larger assemblies, or a batch big enough that sequential runs would take weeks, the walk-in chambers take many units at once. Several of our chambers ramp at over 10 C per minute, which matters for a cycling ESS profile where transition rate does the work.

Monitoring is your call. Units can run powered and instrumented with continuous functional monitoring, powered without monitoring and tested afterwards, or unpowered where the specification calls for storage-condition screening.

Electronics manufacturers shipping in volume. Telecom and networking equipment makers, where field replacement costs make screening standard practice. Aerospace, defence and rail suppliers whose customer specification mandates a screen. Medical device manufacturers building evidence for a design history file. Industrial and instrumentation companies who have had a field failure population they could not explain.

• Your production specification or screening profile, if one exists. If it does not, tell us what you are trying to catch and we will talk it through
• Unit dimensions, weight and quantity per batch
• How units are powered, and whether they need continuous functional monitoring during the run
• The temperature profile: steady dwell or cycling, and the setpoints
• Whether humidity or vibration forms part of the screen
• Your pass and fail criteria, which only your engineers can define
• Fixturing and any harness you supply

Send us your screening specification and batch quantity, and we will confirm the requirement and quote it.