Semiconductor Package Cavities Embed Conductive Traces
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Solution Overview
Problem
Conventional semiconductor packages face issues such as solder bridging, poor electrical connections, delamination, and increased fabrication costs due to the use of lead frames and electroplated projections, which lead to electrical leakage and short circuits.
Innovation Solution
A semiconductor package with a conductive layer having a die pad and peripheral traces, where the traces include finger pads and ends, is encapsulated with cavities deeper than the traces, allowing exposure of the traces for solder ball connection, and a solder mask layer is used to prevent bridging and enhance adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the leads are made flush with the encapsulant surface to reduce package size, then the overall package size is reduced, but solder bridging occurs between adjacent solder balls
Solution Approach 1:
The lead structure is segmented into multiple levels: the lead body is embedded in the encapsulant while the lead end protrudes beyond the encapsulant surface. This segmentation allows the package to maintain compact size while providing exposed lead ends for reliable solder ball attachment, preventing solder bridging between adjacent connections.
2Reliability
If electroplated projections are used to expose conductive surfaces, then electrical connection is improved, but delamination occurs at the interface between antioxidation coating and encapsulant
Solution Approach 1:
The invention extracts and eliminates the problematic antioxidation coating layer that causes delamination. Instead of using electroplated projections with coating interfaces, the patent uses a lead frame structure where the lead body is directly embedded in the encapsulant, removing the source of interface adhesion failure while maintaining electrical connectivity.
3Reliability
If the conductive layer is exposed for solder ball mounting, then electrical connection is enabled, but the conductive layer is susceptible to scratching and damage
Solution Approach 1:
The lead body is preliminarily embedded in the encapsulant during the encapsulation process, before any subsequent handling or mounting operations. This preliminary protective action shields the conductive lead body from mechanical damage such as scratching, while the lead end remains exposed for solder ball attachment, thus maintaining both protection and electrical connectivity.
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 design prevents solder bridging, improves adhesion, reduces the length of bonding wires, and protects the conductive layer from scratching, thereby enhancing electrical reliability and reducing fabrication costs.
Implementation Method 1
the encapsulant has a plurality of cavities with a depth greater than a thickness of the die pad and the traces of the conductive layer for embedding the die pad and the traces therein
Implementation Method 2
a solder mask layer is used to prevent bridging and enhance adhesion
Implementation Method 3
a plurality of bonding wires electrically connecting the chip and the finger pads
Implementation Method 4
a plurality of solder balls formed in the openings of the solder mask layer so as to electrically connect to the trace ends
Data Source
AI summary
A semiconductor package having electrical connecting structures includes: a conductive layer having a die pad and traces surrounding the die pad; a chip; bonding wires; an encapsulant with a plurality of cavities having a depth greater than the thickness of the die pad and traces for embedding the die pad and the traces therein, and the cavities exposing the die pad and the traces; a solder mask layer formed in the cavities and having a plurality of openings for exposing the trace ends and a portion of the die pad; and solder balls formed in the openings and electrically connected to the trace ends. Engaging the solder mask layer with the encapsulant enhances adhesion strength of the solder mask layer so as to prolong the moisture permeation path and enhance package reliability.