Resin Layer Peripheral Thickness for Semiconductor Pad Stress
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Solution Overview
Problem
Semiconductor devices with a postless structure face stress issues due to the difference in thermal expansion coefficients between the semiconductor chip and the mounting substrate, leading to potential fracture of pads and wires connected to solder balls during thermal cycling.
Innovation Solution
A semiconductor device design featuring a resin layer with a locally thicker peripheral portion around through-holes, which absorbs stress caused by thermal expansion differences, reducing the stress on pads and wires connected to external connection terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a postless structure is adopted to simplify the device, then device complexity is reduced, but stress concentration occurs at pad-wire connections due to thermal expansion differences
Solution Approach 1:
The resin layer is designed with non-uniform thickness, featuring a thicker peripheral portion surrounding each through-hole and a thinner central portion. This local quality variation allows the peripheral resin to absorb thermal expansion stress while maintaining structural integrity, preventing stress concentration at the pad-wire connection points without requiring additional protective components.
Solution Approach 2:
The resin layer serves as an intermediary stress-absorbing element between the rigid semiconductor chip and the mounting substrate. By positioning the thicker peripheral resin around the through-holes, it mediates the thermal expansion forces, protecting the vulnerable pad-wire connections from direct stress while maintaining the simplified postless structure.
2Manufacturing precision
If uniform thickness resin layer is used, then manufacturing precision is easier to maintain, but stress distribution is insufficient to protect pad-wire connections
Solution Approach 1:
The resin layer implements local quality variation with distinct thickness zones: a thicker peripheral portion for stress absorption and a thinner central portion for standard manufacturing. This design maintains manufacturing feasibility while providing enhanced stress protection where needed most, around the through-hole perimeters where pad-wire connections are vulnerable.
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
The design effectively reduces stress on pads and wires, thereby suppressing fatigue fractures by distributing thermal expansion stress to the thicker peripheral resin layer portion, enhancing the reliability of the semiconductor device.
Implementation Method 1
the difference in thermal expansion coefficients between the semiconductor chip and the mounting substrate, leading to potential fracture of pads and wires connected to solder balls during thermal cycling
Data Source
AI summary
A semiconductor device includes a semiconductor chip having a wire and a passivation film formed on the outermost surface with an opening partially exposing the wire. A resin layer is stacked on the semiconductor chip and provided with a through-hole in a position opposed to a portion of the wire facing the opening. A pad is formed on a peripheral portion of the through-hole in the resin layer and in the through-hole so that an external connection terminal is arranged on the surface thereof. The peripheral portion of the resin layer is formed more thickly than the remaining portion of the resin layer other than the peripheral portion.