Meaning
High-density interconnection structures in advanced semiconductor packaging connect the silicon die to the substrate, interposer, or another silicon die. The layout of microbump arrays allows thousands of electrical connections to be made across a very small surface area with a pitch below forty micrometers. This technology applies to three-dimensional integrated circuits, high-bandwidth memory modules, and system-on-chip packaging.
It does not apply to traditional wire bonding or standard ball grid arrays with much larger bump pitches.
Manufacturing Process
Electroplating is used to deposit the microscopic solder bumps onto the wafer pads. When fabricating microbump arrays, the pitch between bumps can be as small as ten micrometers. This requires extreme precision in photolithography and plating to prevent bridging and short circuits.
Reliability Challenge
The small volume of each microbump makes the joint susceptible to intermetallic compound formation. In microbump arrays, the entire joint can convert into brittle intermetallic compounds after multiple reflow cycles. This increases the risk of mechanical failure under thermal stress.
Thermal Management
High-density connections generate localized heat that must be dissipated to prevent device failure. Because the microbump arrays are closely spaced, they act as primary thermal paths from the silicon die to the heat sink. This makes co-design of electrical and thermal paths necessary.
