Wafer Level Packaging Solder Ball Thermo-Compression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing wafer level packaging method faces issues with metal dust sticking to grinding blades, leading to inconsistent electrode bump exposure, increased processing costs, and waste of molding compound due to the grinding process.
Innovation Solution
The method involves depositing solder balls on semiconductor chips with varying pad sizes, softening them by heating, and applying pressure with a compression plate to form a planar surface, followed by applying a molding compound and grinding to separate individual chip packages while minimizing residue and excess material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the resin and electrode bump are ground by polishing blade to expose electrode bump, then the electrode bump is exposed from resin, but metal dust from grinding electrode bump sticks to polishing blade causing grinding wheel to stop and inconsistent exposed surface area
Solution Approach 1:
The patent applies preliminary action by controlling the resin thickness before grinding through precise dispensing and curing processes. The resin is applied to a specific thickness that accounts for the electrode bump height, ensuring that after grinding, the electrode bump is exposed at a consistent height without requiring extensive material removal that generates metal dust.
Solution Approach 2:
The patent extracts the harmful metal dust generation by eliminating the grinding of electrode bump entirely. Instead of grinding through resin to expose electrode bump, the method uses a different approach where the electrode bump is exposed by controlling resin application and using alternative removal methods that do not involve grinding metal surfaces.
2Manufacturing precision
If resin is ground and polished to expose electrode bump, then electrode bump is exposed, but expensive molding compound and process time are wasted and additional processing cost is increased
Solution Approach 1:
The patent applies preliminary action by pre-controlling the resin thickness during the dispensing and curing stages. The resin is applied to a precisely calculated thickness that ensures proper electrode bump exposure after minimal or no grinding, eliminating the need for time-consuming extensive grinding operations and reducing material waste.
Solution Approach 2:
The patent skips the time-consuming grinding process by using an alternative approach. Instead of grinding through thick resin layers to expose electrode bumps, the method uses controlled resin application and alternative exposure techniques that rush through the process by eliminating the grinding step entirely or reducing it to a minimal finishing operation.
3Quantity of substance
If solder balls are attached on metal pads with different areas, then larger area pads have bigger volume solder balls or more solder balls, but inconsistent solder ball configuration may affect electrical performance
Solution Approach 1:
The patent applies local quality by varying the solder ball configuration according to the specific requirements of each metal pad location. Different pads receive different numbers or volumes of solder balls based on their area and electrical requirements, optimizing each local position's electrical performance while maintaining overall package consistency through controlled variation.
Solution Approach 2:
The patent applies parameter changes by systematically varying solder ball parameters (number, volume, arrangement) based on pad area and electrical requirements. The method changes these parameters in a controlled manner to achieve optimal electrical performance for each pad configuration while maintaining manufacturing precision through automated placement and consistent process parameters.
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 ensures consistent solder ball exposure, reduces processing costs, and minimizes waste by maintaining control over the surface area and material usage, resulting in efficient and cost-effective chip packaging.
Implementation Method 1
The solder balls are soften by heating the wafer from its back surface, front surface or both. The heating temperature is lower than the melting point of the solder ball.
Implementation Method 2
Alternatively, the compression plate is heated before applying a pressure on it.
Data Source
AI summary
The invention generally relates to a packaging method of an ultra-thin chip, more specifically, the invention relates to a method for packaging the ultra-thin chip with solder ball thermo-compression in wafer level packaging process. The method starts with disposing solder balls on metal pads arranged on the front surface of semiconductor chips that are formed at the front surface of a semiconductor wafer. The solder balls are soften by heating the wafer, a compression plate is applied with a pressure on the top ends of the solder balls thus forming a co-planar top surface at the top ends of the solder balls. A molding compound is deposited on the front surface of the wafer with the top ends of the solder balls exposed. The wafer is then ground from its back surface to reduce its thickness to achieve ultra-thin chip.