Solder bump forming via organic sticking layer
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Solution Overview
Problem
The existing solder bump forming methods face challenges such as misalignment of flux and solder resist openings, leading to improper conductive ball placement, increased manufacturing costs due to the use of conductive ball mounting masks, and variations in pad and opening positions, resulting in short circuits and inefficiencies.
Innovation Solution
A method involving the formation of a metal film capable of chemical reaction with a tackifying compound on pads, followed by the creation of an organic sticking layer, allowing for precise conductive ball placement without a conductive ball mounting mask, using compounds like naphthotriazole derivatives and metal films like Cu or Ni, and optionally incorporating diffusion preventing films to prevent metal diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conductive ball mounting mask is used to place conductive balls on pads, then the placement precision is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The invention extracts and eliminates the conductive ball mounting mask from the process by using a flux forming mask with opening portions that serve dual purposes: defining flux application areas and serving as alignment references for conductive ball placement. This removes the need for a separate conductive ball mounting mask, reducing device complexity while maintaining placement precision through the remaining mask structure.
2Ease of operation
If flux is applied to cover bump forming regions, then conductive balls can be mounted, but misalignment between flux opening and solder resist opening causes improper placement
Solution Approach 1:
The flux forming mask is designed with opening portions that serve multiple functions: (1) defining the flux application area, (2) providing alignment references for conductive ball placement, and (3) ensuring proper positioning relative to solder resist openings. This multi-functional design eliminates the need for separate alignment features and ensures accurate conductive ball placement even when pad or opening positions vary.
3Reliability
If multiple layers including Au layer are formed on pads, then connection reliability is improved, but manufacturing process complexity increases
Solution Approach 1:
The invention applies different metal film layer structures to different regions: pads receive multi-layer structures (Cu/Ni/Au) for high reliability connections, while non-pad regions use simpler structures. The Au layer is selectively formed only where needed for enhanced connection reliability, and the thicknesses of individual layers are optimized locally to balance performance and manufacturing complexity.
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 reduces manufacturing costs and ensures reliable, accurate mounting of conductive balls on pads, enhancing electrical connectivity and reducing the risk of short circuits by eliminating the need for flux and conductive ball masks.
Implementation Method 1
a solution containing the tackifying compound to chemically react to the metal film, thereby forming an organic sticking layer on the metal film
Implementation Method 2
mounting the conductive ball on the pads through the organic sticking layer and the metal film
Data Source
AI summary
A solder bump forming method of carrying out a reflow treatment over a conductive ball mounted on a plurality of pads, thereby forming a solder bump, includes a metal film forming step of forming a metal film capable of chemically reacting to a tackifying compound on the pads, an organic sticking layer forming step of causing a solution containing the tackifying compound to chemically react to the metal film, thereby forming an organic sticking layer on the metal film, and a conductive ball mounting step of supplying the conductive ball on the pads having the organic sticking layer formed thereon, thereby mounting the conductive ball on the pads through the metal film.