Through-Mold Package Connections for Void-Resistant Reflow Mounting
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Solution Overview
Problem
Conventional electronic packages face challenges in mounting to circuit boards due to void formation and defects at the interface between solder balls and solder portions, which can be attributed to the high temperatures of reflow soldering operations causing liquification and mixing of solder phases, leading to inefficiencies and increased manufacturing complexity.
Innovation Solution
The electronic package design incorporates through-mold connections made of alloys like Sn5Sb, with a solidus temperature exceeding the liquidus temperature of intermediate solder portions, allowing for controlled reflow without liquifying the through-mold connections, and eliminating the need for a moat or channel around each solder ball, thereby reducing void formation and simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional reflow soldering operations are performed at high temperatures, then solder portions are liquified and fused to circuit board, but voids and defects form at the interface between solder balls and solder portions
Solution Approach 1:
The patent changes the material parameter of the through-mold connection by using an alloy with a solidus temperature higher than the liquidus temperature of the intermediate solder portion. This parameter change allows the through-mold connection to maintain structural integrity during reflow soldering while the intermediate solder portion liquifies and flows properly, preventing void formation at the interface.
Solution Approach 2:
The patent utilizes controlled phase transitions by selecting materials with different melting characteristics. The intermediate solder portion is designed to liquify during reflow soldering while the through-mold connection remains solid. This differential phase transition enables proper solder flow and wetting without compromising the structural integrity of the through-mold connection, thereby eliminating void formation.
2Ease of manufacture
If conventional solder ball arrays are used with moats or channels, then outgas venting is permitted during laser ablation, but manufacturing complexity increases
Solution Approach 1:
The patent extracts and eliminates the moat or channel feature from the conventional package structure. By removing this unnecessary structural element, the design achieves simpler manufacturing without compromising outgas venting functionality, as the through-mold connection design itself provides adequate pathways for gas escape during the manufacturing process.
Solution Approach 2:
The patent employs composite material strategies by using an alloy for the through-mold connection with a solidus temperature higher than the liquidus temperature of the intermediate solder portion. This material selection creates a functional composite system where the through-mold connection serves multiple purposes: providing structural support, enabling electrical connectivity, and facilitating outgas venting during manufacturing, thereby eliminating the need for separate moat structures.
3Productivity
If conventional solder ball spacing is used, then mounting locations are adequately spaced, but manufacturing efficiency decreases due to larger package footprint
Solution Approach 1:
The patent changes the material parameters of the through-mold connection by using alloys with elevated solidus temperatures. This parameter change enables closer spacing of the through-mold connections without compromising structural integrity during reflow soldering, thereby reducing the overall package footprint and improving manufacturing efficiency through better space utilization.
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 design enhances the reliability of the electronic package mounting by minimizing voids and defects, reducing manufacturing complexity, and allowing for closer spacing of solder balls, thus improving the efficiency and cost-effectiveness of the assembly process.
Implementation Method 1
the through-mold connection configured to have a melting point in excess of a melting point of the intermediate solder portion
Implementation Method 2
The fusing is achieved by a reflow soldering operation in which the package is subject to controlled heat at temperatures sufficient to liquify the solder portions
Data Source
AI summary
Methods are disclosed for manufacturing electronic packages and electronic assemblies. A method of manufacture can include encapsulating electrically conductive through-mold connections with a mold structure and removing a portion of the mold structure to expose the electrically conductive through-mold connections. The electrically conductive though-mold connections can have a higher melting point than solder connections that can connect the electrically conductive through-mold connections to a circuit board. Related electronic packages, electronic assemblies, electronic devices, and methods of mounting an electronic package to a circuit board are disclosed.