Laser Bonding Solder Ball Oxide Removal Underfill
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Solution Overview
Problem
Current methods for fabricating semiconductor packages, particularly those using 3D packages with through silicon via (TSV) technology, face challenges in achieving enhanced process reliability due to limitations in bonding techniques that affect the integrity and efficiency of solder ball connections.
Innovation Solution
A method involving a package substrate with pads, where a semiconductor chip is mounted with solder balls and an underfill resin containing a reducing agent with a carboxyl group is used, and laser irradiation is applied to bond the solder balls to the pads by changing the metal oxide layers to metal layers through heat, enhancing the bonding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bonding techniques are used for solder ball connections, then the process is simpler, but the bonding reliability and connection integrity deteriorate
Solution Approach 1:
The metal oxide layers on the solder ball and pad surfaces are removed in advance through chemical treatment or plasma processing before the bonding step. This preliminary action ensures that when the solder ball contacts the pad, the bonding occurs directly between clean metal surfaces, significantly improving bonding reliability without requiring complex real-time control during bonding
Solution Approach 2:
A eutectic glass composition is introduced as an intermediary material between the solder ball and pad during bonding. The glass composition facilitates bonding at lower temperatures and improves connection integrity by filling gaps and creating a reliable interfacial layer, thereby enhancing bonding reliability while maintaining process feasibility
2Strength
If laser irradiation is applied to bond solder balls to pads, then the bonding strength improves, but the energy consumption and process complexity increase
Solution Approach 1:
The laser bonding process parameters (wavelength, pulse duration, power density) are precisely optimized to match the specific material properties of the solder ball and pad. By changing these parameters to optimal values, strong bonding is achieved with minimal energy input, resolving the contradiction between bonding strength and energy consumption
Solution Approach 2:
Laser irradiation is applied locally only to the specific bonding interface between the solder ball and pad, rather than heating the entire component. This localized energy application achieves the required bonding strength at the critical interface while minimizing overall energy consumption and preventing damage to other parts of the semiconductor device
3Reliability
If metal oxide layers are present on solder ball and pad surfaces, then the surfaces are more stable, but the bonding quality deteriorates
Solution Approach 1:
Metal oxide layers on the solder ball and pad surfaces are removed in advance through chemical treatment or plasma processing before the bonding step. This preliminary action ensures that when the solder ball contacts the pad, the bonding occurs directly between clean metal surfaces, significantly improving bonding quality
Solution Approach 2:
The harmful metal oxide layers are selectively extracted or removed from the bonding surfaces through chemical etching or plasma treatment. By taking out these oxide layers that interfere with bonding, the underlying clean metal surfaces are exposed, enabling high-quality direct metal-to-metal bonding
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 method improves the reliability and efficiency of solder ball bonding, ensuring strong connections and increased process stability, which is crucial for high-performance semiconductor packages.
Implementation Method 1
irradiating the semiconductor chip with a laser to bond the solder ball to the pad, wherein the bonding of the solder ball to the pad comprises changing a metal oxide layer formed on surfaces of the pad and the solder ball to a metal layer by heat generated by the laser
Implementation Method 2
filling a space between the package substrate and the semiconductor chip with a underfill resin including a reducing agent comprising a carboxyl group
Data Source
AI summary
Provided is a method of fabricating a semiconductor package. The method includes providing a package substrate including a pad, mounting a semiconductor chip with a solder ball on the package substrate to allow the solder ball to be disposed on the pad, filling a space between the package substrate and the semiconductor chip with a underfill resin including a reducing agent comprising a carboxyl group, and irradiating the semiconductor chip with a laser to bond the solder ball to the pad, wherein the bonding of the solder ball to the pad comprises changing a metal oxide layer formed on surfaces of the pad and the solder ball to a metal layer by heat generated by the laser.