Integrated circuit package substrate with stepped solder mask op

Details Integrated circuit package substrate with stepped solder mask op Integrated circuit package substrate with stepped solder mask op

1997-11-26

1999-03-30

Picard, Leo P.

Electricity: electrical systems and devices

Housing or mounting assemblies with diverse electrical...

For electronic systems and devices

361764, 361772, 361773, 361774, 361777, 361779, 361783, 257738, 257737, 257778, 257780, 22818022, 438612, 438613, 438108, H05K 114

Patent

active

058896554

ABSTRACT:
A substrate for an integrated circuit package. Located on a bottom surface of the substrate are a plurality of contact pads. Solder balls are attached to the contact pads and then reflowed to mount the package to a printed circuit board. The bottom surface of the substrate has a first layer of solder mask. The first layer has a plurality of first openings which expose at least a portion of each contact pad. Adjacent to the first layer of solder mask is a second layer of solder mask which has a plurality of second openings that also expose the contact pads. The diameter of each second opening is larger than the diameter of each first opening. The openings may be created by etching the layers of solder mask. The etching process typically creates in annular lips in the solder mask openings. The larger second openings reduce the stress risers of the solder balls created by the inner lips of the solder mask.

REFERENCES:
patent: 5034345 (1991-07-01), Shirahata
patent: 5376584 (1994-12-01), Agarwala
patent: 5656863 (1997-08-01), Yasunaga et al.
patent: 5660321 (1997-08-01), Isida et al.

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