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|High Density Interconnect for a High Pin Count Optical IC|
|Keywords: high density interconnect, flexible printed circuit, wire bonding|
|An interconnect solution was developed to connect a large 21x45 mm2 optical IC with 2500 I/O’s to 8 electronic driver boards. The IC had peripheral bond pads in 2 staggered rows with a (single row) pitch of 72 um. In the end application several of these IC’s have to be placed in an array, so the volume available for interconnect was very limited. The routing of some 60 signal lines had restrictions due to signal integrity and each of the 150 power supply lines required a decoupling capacitor to be mounted as close as possible to the IC. On top of that the application required the IC to be mounted with stability in the sub-micron range which put additional requirements on the IC carrier like dynamic decoupling and temperature control. After considering various options, a preferred architecture was selected. The IC was mounted on a water cooled SiC holder with a pin grid seating plane for the IC to ensure maximum flatness. A complex flexible printed circuit board assembly with 5 different bond pad levels was developed in combination with fine pitch aluminium wire bonding. Wire bond geometry was carefully defined and the flex layer build-up was optimized to achieve optimal rigidity. To prove the feasibility of the selected solution, several prototypes were successfully built.|
|Gerard Kums, Sr. Development Engineer
Philips Applied Technologies
Eindhoven, NB 5656AE,