Fine Pitch Interconnect Shape Control via Molding Compound
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Solution Overview
Problem
In the semiconductor industry, the challenge lies in forming reliable interconnects for fine pitch joint assemblies, where solder balls tend to slump and widen during reflow, leading to bridging issues that result in short circuits, especially in densely packed electronic components.
Innovation Solution
The method involves applying a conductive interconnect material with controlled shape and positioning on a substrate, using flux to restrict spread, and a molding compound to provide lateral support, along with controlled heating to prevent slumping, and ensuring the interconnect material contacts the substrate at a specific angle to minimize widening during reflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder balls are used for fine pitch joints, then electrical connections can be established, but the solder balls slump and widen during reflow causing bridging and short circuits
Solution Approach 1:
The interconnect material is applied with a pre-formed controlled shape and positioning before reflow processing. The material is deposited with specific geometric characteristics (narrow base, controlled width) that prevent slumping and bridging during subsequent heating, thereby maintaining spacing precision while ensuring reliable electrical connections
Solution Approach 2:
The patent controls the physical and geometric parameters of the interconnect material during deposition, including width, height, and contact angle. By optimizing these parameters (e.g., contact angle between 30-60 degrees, controlled width-to-height ratio), the material resists slumping during reflow, preventing bridging while maintaining electrical connectivity
2Ease of manufacture
If solder balls are deposited on bonding pads, then interconnects can be formed, but they widen during reflow leading to bridging issues
Solution Approach 1:
The deposition process is controlled to create interconnect material with specific geometric parameters including a narrow base width, controlled height, and optimized contact angle with the substrate. These parameter controls prevent excessive widening during reflow, maintaining manufacturing precision while preserving ease of formation through automated deposition
Solution Approach 2:
The patent replaces traditional mechanical solder ball placement and melting processes with a controlled deposition system that applies material in a pre-formed shape. This substitution allows precise control of interconnect geometry from the outset, eliminating the slumping and widening problems associated with conventional reflow processing
3Strength
If flux is applied to activate the interconnect material, then bonding occurs, but the material spreads and widens
Solution Approach 1:
The interconnect material is deposited with a pre-controlled shape and dimensional constraints before flux application and activation. This preliminary shaping ensures that when flux is applied and bonding occurs, the material maintains its controlled geometry and does not spread excessively, preserving both bonding strength and shape precision
Solution Approach 2:
The deposition process creates local variations in material properties and geometry, such as a narrower base width and controlled sidewall angles in specific regions. These localized geometric features restrict material spread during flux activation and bonding, maintaining precision while ensuring adequate bonding strength at the substrate interface
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for the formation of interconnects with precise spacing and shape, preventing bridging and ensuring reliable electrical connections in high-density semiconductor packages by maintaining the interconnect shape and preventing slumping during reflow.
Implementation Method 1
controlled heating to prevent slumping
Implementation Method 2
using flux to restrict spread
Implementation Method 3
a molding compound to provide lateral support
Data Source
AI summary
Presented herein are an interconnect and method for forming the same, the method comprising forming an interconnect on a mounting surface of a mounting pad disposed on a first surface of a first substrate, the interconnect comprising a conductive material, optionally solder or metal, the interconnect avoiding the sides of the mounting pad. A molding compound is applied to the first surface of the first substrate and molded around the interconnect to covering at least a lower portion of the interconnect and a second substrate may be mounted on the interconnect. The interconnect may comprise an interconnect material disposed between a first and second substrate and a molding compound disposed on a surface of the first substrate, and exposing a portion of the interconnect. A sidewall of the interconnect material contacts the mounting pad at an angle less than about 30 degrees from a plane perpendicular to the first substrate.