Semiconductor Package Copper Pad Solder Mask Bonding
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Solution Overview
Problem
Conventional semiconductor packages face issues with low bonding strength between the solder mask and Ni/Au plating layer, leading to delamination and solder bridges due to the expansion of solder balls during reflow, which decreases yield rates.
Innovation Solution
The use of copper pads exposed directly to the solder mask with an anti-oxidation layer, such as Ni/Au plating or OSP, to enhance bonding strength and prevent solder bridges by maintaining the integrity of the first conductors' position relative to the solder mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the solder mask contacts the Ni/Au plating layer directly, then the structure is simplified, but the bonding strength is low leading to delamination
Solution Approach 1:
The patent introduces an anti-oxidation layer (Ni/Au plating layer) as an intermediary between the copper pad and the solder mask. This mediator prevents direct contact between the solder mask and copper, avoiding oxidation while providing a stable bonding surface that prevents delamination during reflow processing.
2Reliability
If the Ni/Au plating layer is used on copper pads, then oxidation is prevented, but bonding strength with solder mask decreases
Solution Approach 1:
The patent applies different surface treatments to different regions: the anti-oxidation layer (Ni/Au plating) is applied only to the exposed copper pad areas that contact the solder mask, while other areas maintain their original properties. This localized treatment provides oxidation resistance where needed without compromising bonding strength.
3Ease of manufacture
If solder balls are reflowed at high temperature, then soldering is completed, but solder balls expand and cause bridge formation
Solution Approach 1:
The patent applies a solder resist layer over the Ni/Au plating layer before solder ball placement and reflow. This cushioning layer prevents direct contact between expanding solder balls and adjacent conductive elements during high-temperature reflow, eliminating the cause of solder bridge formation while allowing complete soldering.
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 configuration increases the bonding strength between the solder mask and copper pads, preventing solder bridges and improving the yield rate of semiconductor packages by maintaining the structural integrity during the reflow process.
Implementation Method 1
The Ni/Au plating layer 115 is formed on the entire upper surface of the first pad 113
Implementation Method 2
the solder mask contacts the first pads directly, and thus results in higher bonding strength
Implementation Method 3
The molding compound is disposed on the first surface of the substrate, and encapsulates the chip, the conductive elements and the first conductors
Data Source
AI summary
The present invention relates to a semiconductor package. The semiconductor package includes a substrate, at least one chip, a plurality of conductive elements, a plurality of first conductors and a molding compound. The substrate has a plurality of first pads and a solder mask. The first pads are exposed to a first surface of the substrate, and the material of the first pads is copper. The solder mask is disposed on the first surface, contacts the first pads directly, and has at least one opening so as to expose part of the first pads. The chip is mounted on the first surface of the substrate. The conductive elements electrically connect the chip and the substrate. The first conductors are disposed on the first pads. The molding compound is disposed on the first surface of the substrate, and encapsulates the chip, the conductive elements and part of the first conductors. Whereby, the solder mask contacts the first pads directly, and thus results in higher bonding strength, so as to avoid the bridge between the first conductors caused by the first conductors permeating into the interface between the solder mask and the first pads.