Nonconductive Film for Fine Pitch Interconnect Bridging Prevention
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Solution Overview
Problem
In the semiconductor industry, the integration of smaller electronic components requires smaller packages with finer pitch interconnects, but existing solder ball grid arrays face issues with slumping and bridging, which can lead to short circuits due to the widening of solder balls during reflow, especially in fine pitch arrangements.
Innovation Solution
A nonconductive film (NCF) with a controlled thickness and release layer is applied over the connectors to prevent slumping and bridging, providing lateral support and maintaining the shape of the connectors during reflow, thereby allowing for finer pitch interconnects without bridging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If solder ball grid arrays are used to join substrates with finer pitch interconnects, then integration density of electronic components is improved, but solder balls slump and bridge during reflow causing short circuits
Solution Approach 1:
A nonconductive film (NCF) is introduced as an intermediary layer between adjacent solder balls. The NCF provides lateral support to prevent solder ball slumping and bridging during reflow, while allowing vertical compression to establish electrical connections. This mediator resolves the contradiction by enabling fine pitch spacing without compromising connection reliability.
Solution Approach 2:
The nonconductive film functions as a flexible thin film structure that conforms to the solder ball shapes while providing mechanical support. The film's flexibility allows it to accommodate solder ball deformation during reflow, while its structural integrity prevents bridging, thus maintaining both fine pitch capability and connection reliability.
2Reliability
If solder balls are compressed to establish electrical connections, then electrical connectivity is improved, but solder balls widen and bridge adjacent interconnects
Solution Approach 1:
The nonconductive film acts as a spacer that maintains horizontal separation between adjacent solder balls during compression. It allows vertical compression force to transmit through the film to establish electrical connections while preventing lateral spreading that would cause bridging, thus resolving the contradiction between electrical connectivity and interconnect spacing.
Solution Approach 2:
The nonconductive film segments the continuous solder material into discrete, isolated balls by providing physical separation. This segmentation prevents the solder from flowing into adjacent interconnect regions during reflow and compression, maintaining precise interconnect spacing while still allowing electrical connection formation.
3Area of stationary object
If smaller packages are used to accommodate smaller components, then area utilization is improved, but solder ball slumping and bridging increases
Solution Approach 1:
The nonconductive film provides lateral confinement and support to solder balls in compact packages. By acting as a flexible shell structure, it prevents solder ball slumping during reflow in the constrained space of smaller packages, maintaining manufacturing precision while enabling area-efficient packaging.
Solution Approach 2:
The nonconductive film is applied beforehand to provide preventive lateral support to solder balls. This preliminary anti-action counteracts the slumping force that occurs during reflow, preventing shape degradation before it happens, thus maintaining solder ball integrity in smaller packages.
Data Source
AI summary
Disclosed herein is a mechanism for forming an interconnect comprising forming a connector on an interconnect disposed on a first surface of a first substrate and applying a nonconductive material in a non-liquid form over the interconnect after forming the connector. The nonconductive material covers at least a lower portion of the interconnect, and at least a portion of the interconnect is exposed. The nonconductive material is formed around the connector by pressing the nonconductive material over the connector with a roller. An angle between a top surface of the nonconductive material and a connector sidewall between about 65 degrees and about 135 degrees. The nonconductive material may be formed to extend under the connector.