Outer Lead Bend Geometry for Image Sensor Warpage Control
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Solution Overview
Problem
Existing solid-state image sensing apparatuses face issues with warpage and twist due to heat-induced stress, leading to deterioration in picture quality, as conventional outer lead designs either fail to absorb stress effectively or risk short circuits when pitch between leads is narrow.
Innovation Solution
The design incorporates outer leads with a horizontal portion, an orthogonal end portion, a mid portion, a first bend between the horizontal and mid portions, and a second bend between the mid and end portions, forming a right triangle shape, which allows for effective stress absorption and prevention of tilting, even with variations in lead shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If outer leads are designed with simple linear shape, then manufacturing is easy, but stress absorption capability is insufficient leading to warpage
Solution Approach 1:
The outer leads are designed with bend portions having arc-like shapes instead of linear configurations. Each outer lead includes a first bend and a second bend that form curved paths, enabling the leads to flex and absorb thermal expansion stress effectively while preventing warpage of the solid-state image sensing apparatus.
2Volume of moving object
If pitch between outer leads is reduced, then device size is minimized, but risk of short circuit between adjacent leads increases
Solution Approach 1:
The bend portions of adjacent outer leads are positioned at different heights and orientations, creating a three-dimensional separation that prevents contact between leads even when pitch is reduced. The arc-like trajectories of the bends ensure that adjacent leads follow distinct spatial paths, eliminating short circuit risks while maintaining compact dimensions.
3Stability of the object's composition
If outer leads are made rigid, then structural stability is improved, but adaptability to thermal expansion and warpage prevention deteriorates
Solution Approach 1:
The outer leads incorporate flexible bend portions with arc-like shapes that can dynamically adjust their configuration in response to thermal expansion forces. These bend portions act as compliant elements that flex during heating and cooling cycles, allowing the lead structure to adapt to dimensional changes while maintaining overall structural integrity and preventing warpage.
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 effectively controls warpage and twist of the solid-state image sensing apparatus, maintaining image focus and preventing short circuits, while allowing for efficient soldering and stress distribution across the package body.
Implementation Method 1
each of the plurality of the outer leads 2b1 has a bend portion 2b10... When the printed circuit board is expanded in the direction parallel with the long side of the package body 1 (in the x direction) due heat evolution, an end portion A of the outer lead 2b1 fixed to the printed circuit board is caused to move in the x direction. A force pulling the bent portion 2b10 directly below via the end portion A will act on the bent portion 2b10, however, because the bend 2b11 and the bend 2b12 are deformed, a stress exerted on the package body 1 via a root 2b13 of the outer lead 2b1 is controlled.
Data Source
AI summary
Warpage and twist of a solid-state image sensing apparatus is controlled, thereby preventing displacement occurring to the solid-state image sensing apparatus when it is mounted on a printed circuit board. The solid-state image sensing apparatus comprises a plurality of outer leads, and the outer leads each comprises a horizontal portion protruding in the horizontal direction from a side face of a package body for encasing a solid-state image sensing chip therein, an end portion extending in a direction orthogonal to the horizontal portion, and disposed directly below the horizontal portion, a mid portion positioned between the horizontal portion, and the end portion, a first bend formed between the horizontal portion, and the mid portion, and a second bend formed between the mid portion, and the end portion.