Semiconductor Package Interlocking Leads Etching
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Solution Overview
Problem
Semiconductor packages face challenges in withstanding external stresses and forces, leading to lead pull out and wire to wire/wire to die short circuiting, which results in inefficiencies and failures, especially during transportation and usage in electronic devices.
Innovation Solution
The semiconductor package is formed using multiple etching steps, including undercut etching, to create leads with interlocking portions and a thickness greater than the die pad, reducing the wire span and enhancing mechanical interlocking within the package, thereby reducing the likelihood of lead pull out and short circuiting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional single etching step is used to form leads, then manufacturing process is simple, but leads lack interlocking portions and are susceptible to pull out under external stresses
Solution Approach 1:
The etching process is segmented into multiple steps (first etching, second etching, third etching) that progressively form the lead structure with interlocking portions. Each etching step creates specific geometric features that contribute to the overall interlocking capability, transforming a single complex operation into manageable sequential steps.
Solution Approach 2:
The first etching step performs preliminary shaping of the lead structure by removing material to create the basic form and initial geometry. This preliminary action prepares the lead for subsequent etching steps that will form the interlocking portions, allowing the process to build complexity progressively rather than attempting to create the final complex geometry in one step.
2Length of moving object
If lead thickness is reduced to accommodate thinner electronic devices, then package size is reduced, but leads become more vulnerable to external forces and short circuiting
Solution Approach 1:
The invention adds vertical dimensionality to the lead structure through interlocking portions that extend downward into the molding compound. This multi-level geometric configuration (combining horizontal lead body with vertical interlocking features) increases mechanical strength and resistance to pull-out forces while maintaining a thin overall package profile, effectively utilizing three-dimensional space to compensate for reduced material thickness.
Solution Approach 2:
The lead structure functions as a composite system combining the metallic lead material with the surrounding molding compound through mechanical interlocking. The interlocking portions create a composite structure where the lead and molding compound work together to resist external forces, effectively distributing mechanical loads and enhancing overall strength without increasing lead thickness.
3Reliability
If wire span is reduced by making leads thicker, then short circuiting risk decreases, but material usage increases and package size grows
Solution Approach 1:
The interlocking portions extend the lead structure vertically into the molding compound, creating a multi-level geometry that effectively increases the mechanical path length and structural rigidity without proportionally increasing material volume. This three-dimensional configuration provides enhanced short circuit prevention through improved mechanical stability while maintaining material efficiency.
Solution Approach 2:
The interlocking portions feature curved surfaces and rounded geometries that distribute mechanical stresses more evenly throughout the structure. This curvature reduces stress concentration points that could lead to lead failure or wire disconnection, thereby preventing short circuits through improved mechanical reliability rather than simply increasing material thickness.
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 solution significantly reduces the chances of lead pull out and wire to wire/wire to die short circuiting, enhancing the reliability and resilience of semiconductor packages to external stresses and forces, while also ensuring efficient manufacturing with reduced material usage.
Implementation Method 1
a first chemical etching is done to the first side of the first conductive material... a second chemical etching is done to the first side of the first conductive material... a third chemical etching is done to the second side of the first conductive material
Implementation Method 2
both sides of the first conductive material are plated with a second conductive material... open areas of the remaining part of the first conductive material are plated with another layer of a third conductive material
Data Source
AI summary
A semiconductor package formed utilizing multiple etching steps includes a lead frame, a die, and a molding compound. The lead frame includes leads and a die pad. The leads and the die pad are formed from a first conductive material by the multiple etching steps. More specifically, the leads and the die pad of the lead frame are formed by at least three etching steps. The at least three etching steps including a first etching step, a second undercut etching step, and a third backside etching step. The second undercut etching step forming interlocking portions at an end of each lead. The end of the lead is encased in the molding compound. This encasement of the end of the lead with the interlocking portion allows the interlocking portion to mechanically interlock with the molding compound to avoid lead pull out. In addition, by utilizing at least three etching steps the leads can be formed to have a height that is greater than the die pad of the lead frame. This differential in height reduces the span of wires used to form electrical connections within the semiconductor package. These reductions in the span of the wires reduces the chances of wire to wire and wire to die short circuiting because the wire sweep of the wires is reduced when the molding compound is placed.