Optical Module Insulation Walls for Short Circuit Prevention
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Solution Overview
Problem
In optical modules, the use of solder or brazing filler for connecting substrates can lead to short circuits due to lateral spreading, especially with narrower pitches, which affects high-frequency characteristics and impedance mismatch.
Innovation Solution
Incorporating first and second insulation walls made of solder resist between the substrates' pads, ensuring they do not overlap with the pads and are adjacent to each other, to prevent short circuits while maintaining a sufficient bonding area for solder or brazing filler, thus minimizing impedance mismatch and preserving high-frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the solder resist is made to overlap with the connection pad to prevent short circuit, then the short circuit prevention is improved, but the bonding area for solder or brazing filler is reduced and impedance mismatch occurs
Solution Approach 1:
The solder resist is segmented into two distinct functional regions: a first solder resist that overlaps with the connection pad to prevent short circuits, and a second solder resist that does not overlap with the connection pad to maintain bonding area and impedance characteristics. This segmentation allows each region to fulfill its specific function without compromising the other.
Solution Approach 2:
Different regions of the solder resist are given different properties: the first solder resist has overlapping coverage for electrical isolation, while the second solder resist has non-overlapping coverage for mechanical bonding and electrical performance. This local differentiation resolves the contradiction by applying the appropriate solder resist configuration only where needed.
2Reliability
If the space between connection pads is widened to prevent short circuit, then the short circuit prevention is improved, but the pitch between pads increases which is not acceptable
Solution Approach 1:
The first solder resist acts as an intermediary element between adjacent connection pads, providing electrical isolation and preventing short circuits without requiring increased spacing. This mediator allows the pads to maintain narrow pitch while still achieving reliable short circuit prevention through the insulating solder resist layer.
3Strength
If the solder or brazing filler is used to connect substrates, then the bonding strength is improved, but the lateral spreading of solder or brazing filler causes short circuit between connection pads
Solution Approach 1:
The harmful lateral spreading effect of the solder or brazing filler is extracted and controlled by the second solder resist, which is positioned to receive and contain the molten filler material. This allows the bonding strength to be maintained while preventing the unwanted lateral spread that would cause short circuits.
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 effectively prevents short circuits and maintains high-frequency performance by ensuring the insulation walls do not interfere with the pads, allowing for reliable bonding without compromising the bonding area or impedance.
Implementation Method 1
solder or brazing filler for bonding the opposed pair of pads
Implementation Method 2
solder or brazing filler for bonding the opposed pair of pads
Implementation Method 3
a first insulation wall between the first surface and the second surface, between an adjacent pair of the first pads... and a second insulation wall between the first surface and the second surface, between an adjacent pair of the second pads
Data Source
AI summary
An optical module includes: a first substrate with a first surface, the first substrate having some first pads on the first surface; a second substrate with a second surface, the second substrate having some second pads on the second surface, each of the first pads and a corresponding one of the second pads being opposed to each other and constituting an opposed pair of pads; a first insulation wall between an adjacent pair of the first pads, and in contact with the first surface of the first substrate; and a second insulation wall between an adjacent pair of the second pads, and in contact with the second surface of the second substrate. The first insulation wall and the second insulation wall overlap with none of the opposed pair of pads and are adjacent to each other in a direction along the first surface and the second surface.