Integrated Package Alignment Structures for Reliable PoP Stacking
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Solution Overview
Problem
The challenge in Package-on-Package (PoP) assemblies is the difficulty in detecting alignment between stacked packages, leading to low reliability due to potential misalignments caused by confusion between solder balls, metal pads, and patterns in X-ray inspections, resulting in solder joint failures.
Innovation Solution
Incorporating alignment structures outside the interconnection areas on each substrate, which are easily recognizable in X-ray inspections, allowing for accurate alignment verification and adjustment, thereby ensuring proper stacking and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If alignment structures are not added to the package, then the device complexity remains low, but the measurement precision of alignment between stacked packages deteriorates
Solution Approach 1:
The patent introduces alignment structures as intermediary reference objects between the upper and lower packages. These structures serve as mediators for alignment detection, providing distinct reference points that facilitate precise measurement without interfering with the functional interconnection structures. The alignment structures act as a bridge between the two packages, enabling accurate alignment verification through X-ray inspection.
Solution Approach 2:
The alignment structures are designed to create distinct, recognizable patterns in X-ray images that copy or replicate reference geometries. By providing standardized alignment reference patterns on both packages, the system enables precise alignment measurement through image processing and pattern recognition, transforming the alignment detection problem into a pattern matching task.
2Measurement precision
If alignment structures are added outside interconnection areas, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent segments the package surface into functional interconnection areas and non-functional alignment areas. By placing alignment structures outside the interconnection areas, the design separates the alignment function from the electrical connection function. This segmentation allows each area to optimize its specific purpose without interfering with the other, improving alignment detection while maintaining electrical functionality.
Solution Approach 2:
The alignment structures are localized to specific regions outside the interconnection areas, providing local quality enhancement for alignment detection. This localized approach ensures that the alignment reference structures are positioned where they can be easily detected without interfering with the electrical interconnection structures, optimizing both alignment verification and electrical functionality in their respective zones.
3Reliability
If conventional PoP assembly without alignment structures is used, then the manufacturing process is simple, but the reliability deteriorates due to misalignment
Solution Approach 1:
The alignment structures are incorporated into the package design before the stacking and bonding processes. By having pre-formed alignment reference structures on both packages, the manufacturing process can perform alignment verification and adjustment before final soldering, preventing misalignment-related reliability issues. This preliminary alignment verification action ensures proper positioning before irreversible bonding occurs.
Solution Approach 2:
The alignment structures enable feedback mechanisms during the stacking process by providing detectable reference patterns. X-ray inspection systems can detect the alignment structures, provide feedback on alignment status, and allow for adjustment before final bonding. This closed-loop feedback approach ensures accurate alignment, improving solder joint reliability without significantly complicating the manufacturing process.
Data Source
AI summary
An integrated package and a method for making the same are provided. The integrated package includes: a first substrate including: a first interconnection area having a plurality of first interconnection structures; and a first alignment structure disposed outside the first interconnection area; a second substrate stacked above the first substrate and including: a second interconnection area having a plurality of second interconnection structures; and a second alignment structure disposed outside the second interconnection area, wherein the second alignment structure is substantially aligned with the first alignment structure in a stacking direction of the first substrate and the second substrate; and a connecting element disposed between the first substrate and the second substrate and configured for electrically connecting at least one of the plurality of first interconnection structures with at least one of the plurality of second interconnection structures.