Flip Chip

Flip Chip rejection criteria:

Bump coplanarity shall be controlled to +/-15 microns within a die.

BCB window must cover the entire die surface and should not leave any exposed metal on the die surface other than bumping pads.

BCB window should leave 96um +/- 4um clearance on the scribestreet for 6 inch wafers and 121um +/- 4um clearance on the scribe street for 8 inch wafers so there is no adverse impact during sawing operation. Measurement is to be taken at the bottom of the BCB slope.

Wrinkling, cracking, pinholes, lifting or other damage to the BCB layers.

Solder composition for solder bumps is acceptable with +/- 2% variation.

External voids and pin holes on the bump are not acceptable.

Missing or partial bumps are not acceptable.

No residual solder or UBM or foreign materials with cumulative dimension greater than 10% of the bump diameter are acceptable in the field area of the die surface (away from the bumps).

Shorted bumps (bridged by any foreign material or solder) are rejectable.

At right is an example of shorted bumps. There is excess solder extending between two bumps giving the appearance of one large bump.

Misaligned bump causing exposed metalization is rejectable.

Surface condition of the bump must be clear of contaminants.

Any residual photoresist, foreign material, ink or particle present on the wafer is rejectable.

There should be a 2mm solder exclusion area around wafer edge.

Any satellite bumps are rejectable. A satellite is a small secondary solder bump attached to the primary bump.

Any solder that is not part of the device solder bump pattern. Reject any residual solder.

A solder bump that is not circular/spherical in shape or whose diameter is not within +/- 25% of expected diameter.

At left is a solder bump which exceeds 25% of the expected diameter and is rejectable as such.

A solder bump that is very dull in appearance in comparison to others.

A solder bump that is wrinkled.

A solder bump whose shape or height has been damaged.

Any passivation opening on the die without a UBM cap that by design should be covered with UBM.
BCB