IC Package Spacer Ring Controls Solder Overflow
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Solution Overview
Problem
In semiconductor packaging, soft solder overflow during the attachment process can lead to short circuits and uneven bond lines due to thermal conductivity issues, and existing solutions like leadframes with side walls and v-grooves can result in tilted IC dies and movement during solder flow back.
Innovation Solution
A die pad with a spacer ring or dam structure made of dry film solder mask material is used to define solder receiving areas, controlling solder thickness and preventing overflow by repelling solder, ensuring even attachment and stability of IC dies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If soft solder is used to attach the IC die to the die pad, then thermal and electrical conductivity performance is improved, but solder overflow may occur that shorts the pins
Solution Approach 1:
A spacer ring made of solder mask material is introduced as an intermediary element between the die pad and the IC die. This spacer ring defines a solder receiving area that confines the soft solder during attachment, preventing it from overflowing onto the pins while still allowing thermal and electrical conductivity through the solder joint.
Solution Approach 2:
The die pad surface is segmented into a solder receiving area (defined by the spacer ring) and non-solder areas. This segmentation confines the solder to specific regions, preventing uncontrolled flow while maintaining effective thermal and electrical conduction paths.
2Object-affected harmful factors
If leadframe side walls and v-grooves are used to prevent solder overflow, then pin shorting is reduced, but the IC die becomes tilted and bond line thickness becomes non-uniform
Solution Approach 1:
The spacer ring acts as a mediator that provides a flat, level surface for IC die placement. Unlike side walls that create uneven surfaces, the spacer ring's top surface maintains uniform height, ensuring even bond line thickness while still preventing solder overflow through its peripheral containment structure.
3Object-affected harmful factors
If leadframe side walls and v-grooves are used to restrict solder, then overflow is prevented, but IC die movement occurs due to solder flow back effect
Solution Approach 1:
The spacer ring serves as a stable intermediary platform that anchors the IC die in position. Its rigid structure and defined geometry provide mechanical stability that resists solder flow back forces, preventing IC die movement while still allowing the solder to form proper joints within the confined receiving area.
4Object-affected harmful factors
If slots are added to the die pad to restrict solder, then solder flow is limited, but the structure becomes more complex
Solution Approach 1:
Instead of modifying the die pad with slots (adding complexity to the base structure), the solder restriction function is extracted and implemented by a separate spacer ring component. This modular approach achieves solder flow control while keeping the die pad structure simple and maintaining manufacturing efficiency.
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
The spacer or dam structure effectively prevents solder overflow, maintains IC die levelness, and reduces movement due to solder flow back, ensuring reliable electrical and thermal conductivity in single-chip and multi-chip IC packages.
Implementation Method 1
The spacer ring may comprise a dry film solder mask material. The spacer ring advantageously supports the IC die, and controls a thickness of the solder body between the die pad and the IC die.
Implementation Method 2
A die pad with a spacer ring or dam structure made of dry film solder mask material is used to define solder receiving areas, controlling solder thickness and preventing overflow by repelling solder
Data Source
AI summary
A single chip integrated circuit (IC) package includes a die pad, and a spacer ring on the die pad defining a solder receiving area. A solder body is on the die pad within the solder receiving area. An IC die is on the spacer ring and is secured to the die pad by the solder body within the solder receiving area. Encapsulating material surrounds the die pad, spacer ring, and IC die. For a multi-chip IC package, a dam structure is on the die pad and defines multiple solder receiving areas. A respective solder body is on the die pad within a respective solder receiving area. An IC die is within each respective solder receiving area and is held in place by a corresponding solder body. Encapsulating material surrounds the die pad, dam structure, and plurality of IC die.