Flat-Plate Optical Module Package for High-Density Layout
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Solution Overview
Problem
The existing bathtub-shaped optical module packages face challenges in achieving high-density component layout due to insufficient space, leading to reduced fixation accuracy during YAG laser welding and increased risk of stress concentration and cracking in ceramic circuit boards during thermal expansion.
Innovation Solution
A flat-plate-shaped metal package with ceramic circuit boards that change shape along the longitudinal direction, where the non-boundary regions are soldered to the metal base using AuSn solder, reducing stress concentration and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bathtub-shaped package base is used, then hermetic sealing is achieved, but the available space for mounting optical components is insufficient
Solution Approach 1:
The package base is divided into a bathtub-shaped base portion for hermetic sealing and a separate flat-plate-shaped upper portion for component mounting. This segmentation allows each portion to fulfill its specific function optimally - the base portion provides sealing while the upper portion provides mounting space.
Solution Approach 2:
The package structure transitions from a purely three-dimensional bathtub shape to a hybrid structure that incorporates a flat-plate dimension on top. This dimensional change creates additional mounting surface area while preserving the hermetic sealing capability of the original bathtub base.
2Ease of manufacture
If YAG laser welding is performed from the upper side at an angle, then fixation is achieved in bathtub-shaped package, but fixation accuracy is lowered
Solution Approach 1:
The optical component is preliminarily positioned on the flat-plate-shaped upper portion of the package base before welding. This preliminary positioning from the upper side in a flat configuration enables accurate alignment and facilitates subsequent welding without the angular constraints that would reduce precision.
3Reliability
If ceramic circuit board is joined at entire back face to package base, then electrical connection is achieved, but stress concentration and cracking risk increase during thermal expansion
Solution Approach 1:
The ceramic circuit board is joined to the package base only in specific local regions rather than across the entire back face. This selective joining maintains necessary electrical connections while avoiding stress concentration at the boundaries of a full-surface joint, thereby preventing cracks during thermal expansion.
Solution Approach 2:
The joining operation is extracted from being a comprehensive full-surface process to a targeted localized process. Only the necessary portions of the ceramic circuit board back face are joined to the package base, removing the harmful full-surface constraint that causes stress concentration.
4Productivity
If flat-plate-shaped package base is used, then high-density layout is achieved, but package stiffness is reduced
Solution Approach 1:
The package base combines two structural forms - a bathtub-shaped base portion providing stiffness and hermetic sealing, and a flat-plate-shaped upper portion enabling high-density layout. This composite structure integrates the advantages of both forms, maintaining structural rigidity while facilitating dense component arrangement.
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
Enables high-density optical module packaging with reduced risk of ceramic circuit board cracking and improved reliability by distributing stress and facilitating easier YAG laser welding.
Implementation Method 1
a region of the ceramic circuit board not including the first portion is joined to the metal base by soldering
Implementation Method 2
the welding has to be performed from an upper side at an angle unavoidably because the surrounding space is insufficient. The YAG laser welding
Implementation Method 3
if thermal expansion occurs in soldering for board mounting, stress may be concentrated at a boundary portion between the routing portion 91 and the pad portion 92 of the ceramic circuit board 90
Data Source
AI summary
A package for optical module includes a flat-plate-shaped metal base, and a ceramic circuit board in which a plurality of terminals are arranged in a longitudinal direction, and which is joined to an upper surface of the metal base by soldering. The ceramic circuit board has a shape change portion in which the ceramic circuit board is changed in shape along the longitudinal direction, and a region of the ceramic circuit board not including the shape change portion is joined to the metal base by soldering. The shape change portion of the ceramic circuit board is a portion where a width is changed along the longitudinal direction, or a portion where a thickness is changed along the longitudinal direction.