Substrate Ring Bodies Prevent Solder Mask Cracking
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Solution Overview
Problem
Conventional semiconductor packaging substrates face issues with cracking and contamination due to CTE differences between solder mask and solder balls, leading to poor reliability and potential short circuits, especially during reflow and high-temperature tests.
Innovation Solution
A substrate structure with an insulating layer and ring bodies formed in the openings corresponding to the edges of conductive pads, preventing solder material expansion and compression, and maintaining structural integrity by using the same material for ring bodies and insulating layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the projective width of openings is increased to prevent solder material from flowing along circuits, then solder mask cracking is reduced, but substrate space for wiring is reduced and conductive pad delamination may occur
Solution Approach 1:
The opening structure is segmented into multiple functional zones: an first opening for solder ball mounting, an second opening for solder material containment, and a third opening for electrical connection. This segmentation allows each zone to perform its specific function optimally without requiring excessive overall opening width, thus preventing solder mask cracking while preserving substrate wiring space.
Solution Approach 2:
Different regions of the opening structure are assigned different functional qualities: the first opening region allows solder ball placement, the second opening region contains and restricts solder material expansion, and the third opening region provides electrical connectivity. This local differentiation enables precise control of solder material flow without uniformly enlarging all openings, thereby maintaining substrate space efficiency.
2Productivity
If solder balls are used for interconnection, then electrical transmission path is shortened and package size is reduced, but CTE difference causes solder mask layer cracking during reflow
Solution Approach 1:
The second opening acts as an intermediary structure between the solder ball (first opening) and the solder mask layer. It provides a controlled transition zone that manages the thermal expansion and material flow during reflow, absorbing the CTE mismatch stress and preventing direct transmission of cracking forces to the solder mask layer.
Solution Approach 2:
The opening structure with its multiple zones is designed beforehand to cushion and absorb the thermal stress and solder material expansion during reflow. The second opening specifically serves as a cushioning zone that accommodates solder material expansion before it can reach and crack the solder mask layer, thereby protecting the overall structure in advance.
3Object-generated harmful factors
If openings are enlarged to completely expose conductive pads, then solder material flow is prevented, but conductive pad delamination occurs
Solution Approach 1:
The opening structure applies local quality control by creating distinct zones: the first opening exposes the conductive pad sufficiently for solder ball attachment, while the second opening provides a barrier that prevents solder material from flowing beyond the pad edges. This localized functional differentiation achieves solder flow control without requiring complete pad exposure, thereby maintaining pad adhesion strength.
4Area of stationary object
If projective width of openings is reduced, then substrate wiring space is increased, but solder balls compress solder mask layer causing large-area cracking
Solution Approach 1:
The opening is segmented into multiple functional zones that collectively provide the necessary support and control functions. The second opening specifically serves as a support zone that prevents solder mask layer compression and cracking, while the overall compact structure preserves substrate wiring space. This segmentation allows the structure to achieve both space efficiency and reliability.
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
Prevents cracking and contamination, ensures reliable electrical connections, and allows for reduced opening widths without delamination, enhancing the substrate's structural integrity and performance during reliability tests.
Implementation Method 1
a plurality of ring bodies formed in the openings and corresponding in position to edges of the conductive pads
Implementation Method 2
a CTE (Coefficient of Thermal Expansion) difference therebetween easily causes cracking of the solder mask layer
Data Source
AI summary
A substrate structure is provided, which includes: a substrate body having a plurality of conductive pads; an insulating layer formed on the substrate body and having a plurality of openings for correspondingly exposing the conductive pads; and a plurality of ring bodies formed in the openings and corresponding in position to edges of the conductive pads. As such, a plurality of conductive elements can be subsequently formed inside the ring bodies so as to be prevented by the ring bodies from expanding outward during a reflow process, thereby protecting the insulating layer from being compressed by the conductive elements and preventing cracking of the insulating layer.