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SEM Lab, Inc.
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Failure Analysis and Scanning Electron Microscopy
Failure Analysis and Scanning Electron Microscopy

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SEM Lab, Inc. has seen the same type of resistor failures repeatedly since ~ 1997 when we were founded. The trigger appears to be the local environment where the resistors are deployed, for example ...

A computer module in a tractor.
Fireworks display controller. Boards coated with ~ 0.300 inches of Dow Corning "tough gel".
A display at an outdoor drive-up kiosk.
Many other previous analysis efforts where the source of sulfur is unexplained.
The problem, sulfur pollution and corrosion of silver, is illustrated in Fig. A and explained thoroughly in references [1] & [2]. The resistors increase in value and eventually fail open.

http://www.semlab.com/resistorcorrosion.html
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Solder mask misalignment can cause BGA solder joint distortions that weaken individual ball attachments.
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This is a PTH solder joint where the land on the solder side of the board has lifted due to a combination of excessive z-axis expansion of the laminate during wave solder and shrinkage stress in the solder fillet on cool down.
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This is an LED microsection where the open circuit failure was caused by the die and lens material separating from the bottom of the cup and rupturing the die attachment.
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This is a chemically decapsulated SMD diode that failed due to excessive current electrical overstress (EOS).  The bond wire fuses open near the center of the span because it is heat-sunk at both ends.
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This is a flex crack in MLCC caused by breakout of PCBA from panel.  The PCBA layout during the design phase is critical in preventing this type of failure.
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This is an example of "black pad syndrome" (BPS) combined with ball grid array (BGA) warpage causing brittle interfacial fracture between the Ni3Sn4 intermetallic compound (IMC) and the electroless nickel (EN) pad surface on an electroless-nickel immersion-gold (ENIG) finished printed wiring board.
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This is residual activated solder flux on a PCBA.  This causes corrosion of the tin-based solder alloy and copper circuit traces.  It can result in electromigration shorts on the surface of the PCBA.
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One way to identify counterfeit tantalum capacitors is to microsection them and measure the dielectric thickness.   Counterfeits can be relabeled with the wrong voltage rating.

see also http://www.semlab.com/IDCounterfeitParts.html
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