Modulation of Solder Volume to Enable Gap Control during Assembly and Covering of De-Coupling Capacitors between Processor and Laminate
Publication Date: 2016-Mar-07
The IP.com Prior Art Database
Disclosed is a method to utilize a laser to remove a portion of the photoresist before plating in order to better support gap control of solder for traditional C4s and mixed Under Bump Metallization (UBM) systems.
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Modulation of Solder Volume to Enable Gap Control during Assembly and Covering of De -Coupling Capacitors between Processor and Laminate
There is a need for better gap control of solder for traditional C4s and for mixed Under Bump Metallization (UBM) systems. In both cases, it is necessary to have the ability to add solder on given C4s and between given C4s.
The solution is a method to utilize a laser to remove a portion of the photoresist before plating. When it is on one C4, the resist is removed about halfway down (i.e. thickness) to form a larger circular opening than the traditional C4 opening. When this is done to bridge two C4s, the cut patterned is a rectangle that joins two C4s together.
During plating, the openings do not plate until the solder reaches the opened resist. This leads to the creation of a larger area, which causes more solder to be deposited in this region for the same height of solder deposited on adjacent C4s. In the terms of the rectangle, the solder plates between the two C4s in the rectangular region.
During chip joining, the individual C4s have more solder and thus a larger height. For a mixed UBM system, this enables tailoring the amount of solder on top of a pillar without needing to increase the UBM dimensions.
For a device placement between two C4s, the bridged solder enables covering the discrete device with solder to both make the electrical connection and support the device.
An alternative to this is to completely cut through...