Residue under BGA

Electrically conductive residue and corrosion product on the PWB surface under a BGA likely caused reported electrical faults.

BGA residue 1

BSE SEM image of conductive residues on the board surface after prying-off the BGA.

BGA residue 2

EDS spectrum suggests the residue is activated solder flux and dissolved tin.

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Solid-State Relay

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.

Solid State Relay 1

Fig. A – Solid-State Relay

Solid State Relay 2

Fig. B – Decapsulated, bottom side

Solid State Relay 3

Fig. C – Metallic short between pin-5 and an internal circuit

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