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VDDA syndrome on two AMS modules

VDDA syndrome on two AMS modules. This analysis refers to two chips (5 e B) respectively of modules (20210210140103 and 20210210122103) and their mating sensors. If the chip is operated, tha faults appear close to row 32 of columns 10&11 (chip5) and of row 32 of columns 1&2 (chipB).

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VDDA syndrome on two AMS modules

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  1. VDDA syndrome on two AMS modules This analysis refers to two chips (5 e B) respectively of modules (20210210140103 and 20210210122103) and their mating sensors. If the chip is operated, tha faults appear close to row 32 of columns 10&11 (chip5) and of row 32 of columns 1&2 (chipB). The defects will then be in a row lower than 32 in both cases. The observation at the optical microscope confirms the presence of a deposit at the row 20&21 of chip5 and 28 of chipB. chipB chip5 Riga 20 Riga 28 Leonardo Rossi

  2. Similar deposits are on the mating (note: all pictures (including the x-rays) are taken with the bumps toward the camera). It is evident that the residue on chip5 is still taller than adjacent bumps and therefore risks to cause another VDDA syndrome in the chip we are going to flip again.. This is also confirmed in the “side view” of the chip (see next page). Leonardo Rossi

  3. Blow-up of chip5, col 10&11, row 21&22 Side view of chip5, col 10&11, row 21&22 Side view of chip5, col 10&11, row 15 (a typical bump pair). Leonardo Rossi

  4. Sensors and chips are then observed at the x-ray mchine to see if the debris is visible (I.e. of high Z). Row 20 chip5 Col 10&11 Leonardo Rossi

  5. Sensor in front of chip5 Row 20 Col 10&11 Leonardo Rossi

  6. chipB Row 28 Col 1&2 Leonardo Rossi

  7. Sensor in front of chip B Row 28 Col 1&2 Leonardo Rossi

  8. I then conclude that the debris is invisible at x-rays and has therefore low Z. The most likely explanation is that it is made out of Silicon of the wafer or Diamond of the blade. Leonardo Rossi

  9. Before sending the module 20210210140103 to be reworked I take out with a manipulator the excess material around [col10&11, row 21&22]. The operation eliminates the exess material but, unavoidably, scratches the pixel pads (row 21, col 10 e col 11). Leonardo Rossi

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