Solder Bump Correction Using Patterned Mask
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Solution Overview
Problem
Existing methods for forming solder bumps on silicon wafers, such as using solder paste, solder balls, or molten solder, often result in defects or insufficient solder, leading to the entire wafer being discarded due to the inability to correct fine pattern issues effectively.
Innovation Solution
A method involving a mask with holes matching the solder bumps pattern is used to cover the defective or insufficient solder bumps, allowing molten solder to fill in the defects, enabling correction and uniform height control of the bumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If solder paste is used to form solder bumps, then manufacturing cost is reduced, but manufacturing precision deteriorates due to lower limit on separation for printing
Solution Approach 1:
A mask is introduced as an intermediary component between the solder bump formation process and the substrate. The mask with precisely positioned holes enables accurate solder bump formation by controlling where solder material is deposited, while allowing the use of cost-effective solder paste or molten solder dispensing methods.
2Manufacturing precision
If solder balls are used to form solder bumps, then manufacturing precision is improved for fine circuit patterns, but manufacturing cost increases
Solution Approach 1:
The invention changes the state of solder material from solid solder balls to molten solder or solder paste, allowing for more cost-effective dispensing methods while maintaining precision through the mask. The mask controls the deposition pattern, enabling fine circuit pattern formation without requiring expensive pre-formed solder balls.
3Productivity
If solder bumps are collectively formed on the entire workpiece, then productivity is improved, but reliability deteriorates when defects occur in fine pattern solder bumps
Solution Approach 1:
The invention segments the solder bump formation process into two stages: (1) collective formation of solder bumps using efficient bulk methods, and (2) selective correction of defective bumps using a mask and targeted solder replenishment. This segmentation allows maintaining high productivity while improving reliability by addressing defects without discarding the entire workpiece.
Solution Approach 2:
The mask is prepared in advance with hole patterns matching the solder bump locations. This preliminary preparation enables selective correction of defective bumps by allowing solder to be supplied only to specific locations through the mask holes, rather than requiring complete reformation of all bumps.
4Reliability
If a mask is placed on solder bumps to supply molten solder selectively, then reliability is improved by correcting defective bumps, but device complexity increases
Solution Approach 1:
The mask creates a copy or replica of the desired solder bump pattern through its hole arrangement. This simple replicated structure enables precise control of solder deposition without requiring complex positioning systems or control mechanisms, as the mask itself defines the deposition pattern.
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 allows for the reuse of silicon wafers with defective solder bumps, reducing material costs and simplifying the process by enabling uniform height control of solder bumps, even when formed using methods like solder balls, thus preventing wafer discard.
Implementation Method 1
molten solder is caused to come into contact with the solder bumps through the mask so as to fill hole portions of the mask with the molten solder
Implementation Method 2
a mask in which holes are formed with the same pattern as the solder bumps is placed on the solder bumps so as to cover the solder bumps
Data Source
AI summary
A pattern formed on a silicon wafer is fine so that solder bumps formed on the silicon wafer are also fine and hence, when a failure occurs, the failure cannot be corrected so that an entire silicon wafer as a workpiece is discarded. Provided is a correction method where, on solder bumps formed on the silicon wafer, a mask in which holes are formed with the same pattern as the solder bumps is placed so as to cover the solder bumps and, thereafter, molten solder is caused to come into contact with the solder bumps through the mask thus filling hole portions of the mask with the molten solder.