Imaging Element Wire Bond Structure for Pad Opening Clearance
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Solution Overview
Problem
In imaging element packages, the risk of disconnection and interference of wire wiring is high due to stress and uneven heat generation, especially with thicker solid-state imaging elements, leading to potential disconnection during reflow and thermocompression bonding, and interference with the side surfaces of the opening for the pad.
Innovation Solution
The implementation of a wire wiring structure that includes a ball portion bonded to the pad with a thickness equal to or larger than the depth of the opening, and a crescent portion formed by pressing the metal wire end against the ball portion, with a connection length of a predetermined ratio or more, to enhance bonding strength and prevent disconnection and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a thicker solid-state imaging element is used, then stress during processing is reduced, but wire wiring may disconnect due to increased stress on stitch bond portion
Solution Approach 1:
The wire wiring is divided into distinct portions: a ball portion bonded to the pad, a crescent portion formed by pressing the metal wire end against the ball portion, and a connection length portion. This segmentation allows each portion to fulfill specific functions - the ball portion provides bonding surface, the crescent portion distributes stress, and the connection length ensures mechanical strength, collectively preventing disconnection while accommodating thicker imaging elements.
Solution Approach 2:
Different portions of the wire wiring are given different geometric characteristics tailored to their specific functions. The ball portion has a spherical shape for bonding, the crescent portion has a compressed arc shape for stress distribution, and the connection length has sufficient length for mechanical strength. This local optimization ensures each region performs its function effectively, resolving the contradiction between stress reduction and connection reliability.
2Temperature
If a thicker solid-state imaging element is used, then heat generation unevenness is reduced, but wire wiring may interfere with side surface of opening
Solution Approach 1:
The ball portion thickness is designed to extend vertically to at least the depth of the opening, effectively utilizing the vertical dimension to clear the opening path. This dimensional approach ensures the wire wiring connects pads on thicker imaging elements without interfering with the side surfaces of openings, while the horizontal projection of the ball portion remains within the pad area to avoid lateral interference.
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 solution effectively reduces the risk of disconnection and interference, improving the reliability of the imaging element package by maintaining bonding strength and preventing damage during processing and thermal expansion.
Implementation Method 1
the solid-state imaging element and the semiconductor mounting substrate are connected by a wire wiring formed by wire bonding
Implementation Method 2
a crescent portion provided by pressing an end of the metal wire against the ball portion and bonding the end to the ball portion
Implementation Method 3
a resin sealing structure for sealing the wire wiring with resin is adopted
Implementation Method 4
an imaging element package in which a plurality of solder balls is arranged in a lattice pattern on a lower surface of a semiconductor mounting substrate
Data Source
AI summary
The present disclosure relates to an imaging element package, a method of manufacturing the same, and an electronic device capable of further improving reliability. An imaging element package includes a solid-state imaging element having a first pad, a substrate on which the solid-state imaging element is mounted, the substrate having a second pad, and a wire wiring that connects the first pad and the second pad. The wire wiring has a ball portion bonded to the first pad in a shape having a thickness equal to or larger than a depth of an opening portion provided for opening the first pad, and a crescent portion provided by pressing an end of the metal wire against the ball portion and bonding the end to the ball portion, and connected to the metal wire with a connection length of a predetermined ratio or more with respect to the metal wire.