Planar Transformer Pad Stacking for Stronger Wire Bonding
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Solution Overview
Problem
Conventional methods struggle to thicken wire bonding pads on transformer elements without affecting coil characteristics, leading to inadequate bond strength and potential damage to the transformer element.
Innovation Solution
A transformer element design where pads are formed thicker than the coils, with specific insulating films and manufacturing processes ensuring the pads cover the coils partially, allowing for increased thickness without compromising coil characteristics, and a method to manufacture these elements with distinct pad formation processes to enhance bond strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the wire bonding pad is thickened to improve wire bonding operability, then the wire bonding strength is improved, but the coil characteristics are adversely affected
Solution Approach 1:
The pad structure is divided into two distinct parts: a first pad layer formed together with the coil that maintains thin thickness for optimal coil characteristics, and a second pad layer formed separately and stacked on the first pad that provides additional thickness for improved wire bonding strength. This segmentation allows each part to fulfill its specific function independently without compromising the other.
Solution Approach 2:
Instead of increasing pad thickness in the horizontal plane which would interfere with coil formation, the solution adds thickness in the vertical dimension by stacking a second pad layer on top of the first pad layer. This dimensional approach allows pad thickening without affecting the coil's planar structure and magnetic characteristics.
2Ease of operation
If the pad thickness is increased to improve wire bonding operability, then the bond strength is improved, but the manufacturing complexity increases
Solution Approach 1:
The first pad layer is formed in advance during the coil fabrication process using the same conductive film and patterning steps, so no additional manufacturing steps are required for the pad base structure. This preliminary formation simplifies the overall process by integrating pad creation with coil creation.
Solution Approach 2:
The first pad layer acts as an intermediary structure that is already present when the second pad layer is formed. This intermediary layer provides a prepared substrate that simplifies the formation of the thickened pad, as the second layer only needs to be deposited on top of the existing first layer rather than being formed from scratch.
Data Source
AI summary
To provide a transformer element in which pads for wire bonding are made thick while suppressing influence on coil characteristics. A transformer element includes a first coil having a planner shape, a first insulating film provided on an upper side of the first coil, a second coil having a planner shape opposite to the first coil provided on the first insulating film, a first pad provided on the first insulating film and connected to a side of one end of the second coil, a second pad provided on the first pad, and a second insulating film provided on the first insulating film and the second coil so as to cover the second coil, in which an aggregate thickness of the first pad and the second pad is thicker than the second coil, and the second pad at least partially covers the second insulating film.