Coining Solder Balls for IC Package Warpage Control
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Solution Overview
Problem
Large IC packages face warpage issues, leading to fabrication defects during board assembly due to non-coplanar solder balls, which become more challenging as package sizes increase, affecting manufacturing quality and in-field reliability.
Innovation Solution
The technique involves using a coining process with a planar or nonplanar coining plate to flatten and adjust the height of solder balls in a ball grid array package, ensuring coplanarity by pressing a coining plate against the solder balls to impose a desired profile, thereby improving overall coplanarity and reducing warpage effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If IC package size is increased to accommodate larger circuits, then the package can handle more complex applications, but warpage control becomes increasingly difficult
Solution Approach 1:
The coining process is performed before board assembly to pre-flatten the solder balls and compensate for anticipated warpage. By applying controlled pressure to the solder balls in advance, the package is prepared to maintain coplanarity during subsequent assembly processes, preventing fabrication defects that would otherwise occur with large package sizes.
Solution Approach 2:
The coining process changes the physical parameters of the solder balls by applying controlled pressure to flatten their surfaces and adjust their heights. This modifies the mechanical properties of the solder ball array, creating a compensated profile that counteracts warpage effects and maintains manufacturing precision despite increased package size.
2Manufacturing precision
If solder ball coplanarity is improved through coining, then manufacturing quality increases, but additional process steps are required
Solution Approach 1:
The coining process combines multiple functions into a single operation: it flattens the solder ball surfaces, adjusts their heights, and compensates for warpage all at once. By integrating these functions into one process step using a coining plate with specific surface profiles, the method achieves improved coplanarity without requiring multiple separate process steps.
Solution Approach 2:
The coining plate serves as an intermediary tool that transfers the desired coplanar profile to the solder balls. Rather than directly manipulating each solder ball individually, the coining plate acts as a mediator that simultaneously shapes multiple solder balls, simplifying the process while achieving precise coplanarity control.
3Manufacturing precision
If a nonplanar coining plate surface is used to impose desired profiles, then coplanarity control is improved, but the coining apparatus complexity increases
Solution Approach 1:
The coining plate features localized variations in surface geometry, with different regions having specific profiles tailored to compensate for warpage in corresponding areas of the package. This local quality approach allows precise control of coplanarity in different zones without requiring complex overall apparatus design, as each region of the coining plate is optimized for its specific function.
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 effectively reduces warpage-related defects, enhances manufacturing quality, and improves reliability by ensuring solder balls are in the same plane, reducing thermal stresses and the risk of component damage during assembly, without requiring changes to packaging design or materials.
Implementation Method 1
pressing a pressing plate against two or more of the solder balls, coining the two or more solder balls until each solder ball has a desired coined surface profile
Data Source
AI summary
A method includes positioning an integrated circuit package in a coining apparatus having a fixture and a pressing plate. The integrated circuit package includes a substrate, an integrated circuit device disposed on a top surface of the substrate, and a plurality of solder balls disposed on a bottom surface of the integrated circuit package. The fixture includes a support structure and a cavity. The cavity receives the integrated circuit device while the support structure supports portions of a top surface of the integrated circuit package. The pressing plate is pressed against two or more of the solder balls, coining the two or more solder balls until each solder ball has a desired coined surface profile.