Pure tin plating is problematic especially in applications like flex connectors where mechanical stress is a given.
Here is a tin whisker just off of the crimp connection.
Here is a second tin whisker.
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BSE SEM image of stock diode sample.
A crack is present in the glass body.
There were fractures in the glass case near the terminations on all of the stock diodes examined. There is significant risk that these fractures would propagate to failure due to expected assembly and use stresses.
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EDS shows Teflon (or some other fluorine-rich material) contamination on gold plated contact pads on the PWB.
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Pure tin plating on this flex cable connector contact produced a tin whisker.
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Electrically conductive residue and corrosion product on the PWB surface under a BGA likely caused reported electrical faults.
BSE SEM image of conductive residues on the board surface after prying-off the BGA.
EDS spectrum suggests the residue is activated solder flux and dissolved tin.
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256K x 16 Bit CMOS Video RAM
64-Pin SSOP package
Post decapsulation BSE SEM image of fuse banks on the die surface.
Fuse blown (on purpose) to configure device.
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The device exhibited a metallic short between pin-5 and an internal circuit element (a resistor that would normally be isolated). The short appeared to be solder material (primarily tin) from the pin-5 termination that flowed into the device due to excessive temperature exposure during assembly.
Fig. A – Solid-State Relay
Fig. B – Decapsulated, bottom side
Fig. C – Metallic short between pin-5 and an internal circuit
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This Base-Metal-Electrode Multilayer-Chip-Capacitor (BME MLCC) exhibited some type of manufacturing problem with knit line fractures and excessive internal porosity.
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Optical image of glass rectifier diode.
The location of the diode breakdown site at the edge of die and the size of the melt pipe suggest this is ESD damage.
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