Via Plug Interposer for High-Frequency Signal Integrity
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Solution Overview
Problem
High-frequency signal transmission in hybrid land grid arrays (HLGAs) is hindered by signal reflections and degradation due to circuitous signal paths and geometry changes, leading to manufacturability issues when attaching solder balls directly over via openings, as flux can flow and cause unintended soldering and reduced solder volume.
Innovation Solution
Plugging via holes with metal plugs or compliant pins to prevent flux and solder from entering, ensuring a direct signal path and maintaining solder volume, which can be achieved through press-fit or soldered connections, and using sintered or solid via plugs to secure solder balls and prevent flux from climbing via walls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If solder balls are attached directly over via openings, then the attachment process is simplified, but flux flows into the via causing unintended soldering and reduced solder volume
Solution Approach 1:
A via plug is introduced as an intermediary component to block the via opening. This plug prevents flux and solder from entering the via while providing a surface for solder ball attachment, thus resolving the conflict between simplified attachment and joint quality
Solution Approach 2:
The via plug is installed before solder ball attachment to pre-prevent flux infiltration. This preliminary blocking action ensures that subsequent soldering operations are not compromised by flux entering the via
2Manufacturing precision
If via holes are left open for signal transmission, then signal path is direct, but flux climbs via walls causing manufacturing defects
Solution Approach 1:
The via plug acts as a mediator that blocks the via opening to prevent flux climbing while allowing the signal path to remain direct through the plug structure itself
Solution Approach 2:
The via plug, which initially seems to obstruct the via, actually benefits the manufacturing process by preventing flux infiltration and enabling precise solder ball placement, thus converting a potential harm into a benefit
3Quantity of substance
If metal plugs are inserted into via holes to prevent flux entry, then solder volume is maintained, but the process complexity increases
Solution Approach 1:
The via plug is designed to be self-installing through press-fit into the via hole, eliminating the need for complex external installation equipment or processes while effectively maintaining solder volume
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 reduces signal reflections and degradation by providing a direct signal path and ensuring a successful bond between solder balls and the interposer, enhancing signal strength and reliability during high-frequency communication.
Implementation Method 1
heating the sintering paste to a temperature at which the sintering paste solidifies, resulting in a sintered via plug
Implementation Method 2
heating the solder ball to a temperature at which the solder ball bonds to the sintered via plug
Data Source
AI summary
An interposer comprises a metal-plated via that spans the depth of a printed circuit board. The interposer also comprises a metal plug inserted into a first end of the metal-plated via. The metal plug is attached to the metal-plated via. The metal plug may take the form of a solid plug or a sintered via plug. The interposer also comprises a solder ball soldered to the metal plug.