Package-on-Package PCB Design for Thickness and Reliability
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Solution Overview
Problem
Existing printed wiring boards for package-on-package (POP) face challenges in reducing thickness while maintaining mounting reliability, as they often require conductor pattern mounting pads and can experience fine peeling or shape defects at interfaces between pads and via conductors.
Innovation Solution
A printed wiring board design featuring a first insulating layer with through holes and electrodes, a laminated second insulating layer with first and second pads, and via conductors that connect these pads to a conductor pattern, eliminating the need for conductor pattern mounting pads and reducing thickness by using exposed electrodes for direct mounting and improving reliability through stress relaxation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductor pattern mounting pads are used in existing POP printed wiring boards, then electrical connection is achieved, but thickness reduction is limited and interface peeling defects occur
Solution Approach 1:
The invention extracts and eliminates the conductor pattern mounting pad layer from the traditional POP structure. Instead of using separate conductor patterns for mounting pads, the design directly forms pads on the insulating layer surface, removing the unnecessary intermediate conductor pattern layer and reducing overall thickness while maintaining mounting functionality.
Solution Approach 2:
The invention inverts the traditional approach by forming pads directly on the insulating layer surface rather than creating them through conductor patterns. This reversal of the conventional pad formation method eliminates the need for thick conductor pattern layers and reduces the overall board thickness while improving structural integrity.
2Reliability
If conductor pattern mounting pads are used, then electrical connection is established, but fine peeling and shape defects occur at pad-via conductor interfaces
Solution Approach 1:
The invention merges the pad formation process with the insulating layer structure itself. By forming pads directly on the insulating layer surface and integrating via conductors within the same insulating layer, the design eliminates the separate interface between conductor patterns and via conductors, thereby preventing fine peeling and shape defects at these interfaces.
Solution Approach 2:
The insulating layer serves as an intermediary structure that directly supports both the pads and via conductors. This mediator approach eliminates the need for separate conductor pattern layers, reducing the number of interfaces and preventing defect formation at pad-via conductor boundaries.
3Reliability
If traditional multi-layer structure with conductor patterns is used, then electrical connection is achieved, but device complexity and thickness increase
Solution Approach 1:
The insulating layer is given multiple functions: it provides mechanical support, forms the substrate for pads, and contains via conductors. This multi-functional design eliminates the need for separate conductor pattern layers, reducing structural complexity while maintaining reliable electrical connections through the integrated pad-via conductor system.
Data Source
AI summary
A printed wiring board for package-on-package includes a first insulating layer, a wiring layer including a conductor pattern and formed on first surface of the first insulating layer, a second insulating layer formed on first surface side of the first insulating layer, electrodes formed in through holes of the first insulating layer respectively such that the electrodes electrically connect to the conductor pattern and have exposed surfaces exposed from second surface of the first insulating layer, first pads formed on the second insulating layer and positioned to connect an IC chip in center portion of the second insulating layer, second pads formed on the second insulating layer and positioned in outer edge portion of the second insulating layer to connect a second printed wiring board, and via conductors formed in the second insulating layer such that the via conductors electrically connect the first and second pads to the conductor pattern.