PoP Device Smooth Pad Solder Connection
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Solution Overview
Problem
Package on package (PoP) devices face issues with weak and unreliable solder connections due to rough surfaces caused by laser ablation, leading to poor signal quality and performance, particularly in mobile and wearable devices.
Innovation Solution
A PoP device design featuring a smooth pad surface with a low Ra value, achieved by avoiding laser processing on the pad, and using solder on the pad before forming the encapsulation layer, which enhances the reliability of solder connections and signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser ablation is used to remove encapsulation layer, then encapsulation layer removal is achieved, but pad surface becomes rough leading to weak solder joints
Solution Approach 1:
The patent applies preliminary action by forming the encapsulation layer to cover the pad surface before soldering, then selectively removing only the encapsulation layer (not the pad) through laser ablation or mechanical means. This preserves the smooth pad surface while achieving encapsulation layer removal, preventing the roughness problem that would occur if laser ablation were applied directly to the pad.
Solution Approach 2:
The encapsulation layer acts as an intermediary that protects the pad surface during processing. By removing the encapsulation layer selectively without damaging the underlying pad, the patent uses this intermediary structure to enable encapsulation removal while maintaining pad integrity and smoothness for reliable solder joints.
2Ease of manufacture
If rough pad surface is accepted, then manufacturing process is simpler, but signal quality and joint reliability deteriorate
Solution Approach 1:
The patent forms the encapsulation layer in advance to cover the pad, then selectively removes it to expose the smooth pad surface. This preliminary encapsulation and selective removal approach maintains manufacturing simplicity while ensuring high signal quality through preserved pad smoothness.
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 solution provides robust and reliable solder connections, improving signal and power transmission between packages, while maintaining a cost-effective and compact form factor suitable for mobile and wearable devices.
Implementation Method 1
an encapsulation layer encapsulating the first die and the package interconnect
Implementation Method 2
a first solder interconnect coupled to the first package, and a second package coupled to the first package through the first solder interconnect
Data Source
AI summary
Some features pertain to a package on package (PoP) device that includes a first package, a first solder interconnect coupled to the first integrated circuit package, and a second package coupled to the first package through the first solder interconnect. The second package includes a first die, a package interconnect comprising a first pad, where the first solder interconnect is coupled to the first pad of the package interconnect. The second package also includes a redistribution portion coupled to the first die and the package interconnect, an encapsulation layer at least partially encapsulating the first die and the package interconnect. The first pad may include a surface that has low roughness. The encapsulation layer may encapsulate the package interconnect such that the encapsulation layer encapsulates at least a portion of the first solder interconnect.