Bond Wire Bump Landing for Better Solder Wetting in Packages
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Solution Overview
Problem
Flip-chip packaging faces reliability issues due to solder joint cracking and mold material delamination, which can be exacerbated by inadequate bond line thickness and surface roughening, leading to reduced chip level reliability and increased manufacturing costs.
Innovation Solution
The use of bond wires on top metal attachment locations of support structures, such as multilevel package substrates or lead frames, facilitates improved solder wetting and adherence by creating a mesh structure that enhances bond line thickness and mechanical strength, thereby reducing the risk of solder joint cracking and delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If surface roughening techniques are used to prevent mold material delamination, then adhesion between lead frame and mold is improved, but solder wetting deteriorates due to copper oxide growth acting as a diffusion barrier
Solution Approach 1:
The patent applies different surface treatments to different regions: the lead frame surface is roughened in non-solder areas to prevent mold delamination, while the solder bump landing areas are kept smooth and protected from oxidation to ensure proper solder wetting. This spatial differentiation of surface properties resolves the contradiction between adhesion and soldering quality.
Solution Approach 2:
The patent introduces an intermediary protective layer (such as electroplated copper or other protective coatings) over the roughened lead frame surface in solder areas. This intermediary layer prevents copper oxide formation while allowing the underlying roughened structure to maintain mold adhesion, thus mediating between the two conflicting requirements.
2Reliability
If taller copper bump or conductive terminals are used to mitigate reduced bond line thickness, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies preliminary surface preparation and protective plating to the lead frame before die attachment. By pre-treating the surface to optimize solder wetting and bond formation, the process achieves reliable bonds with standard bump heights, avoiding the need for taller, more expensive copper bumps or conductive terminals.
3Stability of the object's composition
If selective lead frame plating is used to address separation or delamination, then mold material adhesion is improved, but manufacturing cost increases
Solution Approach 1:
The patent selectively applies protective plating only to specific regions of the lead frame where solder bumps will be attached, rather than plating the entire lead frame surface. This localized approach provides the necessary adhesion protection and solder wetting enhancement while minimizing material costs and manufacturing complexity compared to complete lead frame plating.
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 approach enhances chip level reliability and electronic device performance by ensuring robust solder connections and preventing delamination, while maintaining manufacturing efficiency and reducing costs associated with surface roughening and additional materials.
Implementation Method 1
bond wires on top metal attachment locations of support structures... facilitates improved solder wetting and adherence by creating a mesh structure that enhances bond line thickness and mechanical strength
Data Source
AI summary
An electronic device includes a semiconductor die, a support structure and bond wires, where the semiconductor die has a semiconductor body, a metallization structure over the semiconductor body, and a conductive terminal, the metallization structure includes a top level that extends in a plane of orthogonal first and second directions, the conductive terminal extends away from the plane along an orthogonal third direction, and the support structure has a conductive metal feature with an attachment location. The bond wires are on the attachment location and a package structure at least partially encloses the semiconductor die and a portion of the support structure, where the conductive terminal is soldered to the attachment location of the conductive feature over at least some of the bond wires.