US Patent 8653658 Planarized bumps for underfill control

The mechanisms for forming bump structures reduce variation of standoffs between chips and package substrates. By planarizing the solder layer on bump structures on chips and/or substrates after plating, the heights of bump structures are controlled to minimize variation due to within die and within wafer locations, pattern density, die size, and process variation. As a result, the standoffs between chips and substrates are controlled to be more uniform. Consequently, underfill quality is improved.