Semiconductor Assembly Solder Removal to Prevent Package Delamination
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Solution Overview
Problem
Existing methods of manufacturing semiconductor assemblies are prone to delamination due to stress from thermal expansion and mechanical deformation, leading to potential device failure from moisture ingress.
Innovation Solution
A method involving securing a die to a die paddle with solder, forming a subassembly, heating to reflow, removing solder from the die paddle adjacent to the die, and moulding a casing onto the subassembly to improve bond strength and reduce delamination risk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If solder is applied to secure the die to the die paddle and is allowed to spread during reflow, then the die is firmly attached to the die paddle, but the bond strength between the casing and the subassembly is reduced leading to delamination
Solution Approach 1:
The patent removes excess solder from the die paddle surface after reflow processing. This extraction of the harmful element (excess solder) eliminates the weak bonding area while preserving the strong die-to-paddle attachment, thereby preventing casing delamination without compromising the primary joint strength
Solution Approach 2:
The patent performs solder removal as a preliminary step before casing moulding. By removing excess solder beforehand, the surface is prepared to provide optimal bonding conditions for the casing, ensuring strong adhesion from the start rather than attempting to correct bonding issues afterward
2Strength
If solder spreads beyond the die footprint during reflow, then the die is securely mounted, but the exposed die paddle area for casing bonding is reduced
Solution Approach 1:
The patent selectively removes solder from regions of the die paddle where it has spread beyond the die footprint. This extraction restores the available bonding area on the die paddle surface without affecting the solder joint that secures the die, thereby resolving the trade-off between mounting strength and bonding area
Solution Approach 2:
The patent applies different treatments to different regions of the die paddle: the solder joint area under the die is preserved to maintain mounting strength, while the peripheral areas where solder spread occurs are cleaned to maximize bonding area for the casing
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
The method enhances the bond strength between the casing and the subassembly, reducing the likelihood of delamination and subsequent device failure, particularly in assemblies with higher die-to-paddle area ratios.
Implementation Method 1
heating the first subassembly to at least the melting temperature of the solder
Implementation Method 2
The solder may be removed from the die paddle using laser ablation
Data Source
AI summary
A method of manufacturing a semiconductor device is provided. The method includes securing a die to a die paddle with solder and securing a clip to the die with solder to form a first subassembly. The method further includes heating the first subassembly to at least the melting temperature of the solder, then subsequently removing at least some of the solder from the die paddle in a region adjacent the die to expose the die paddle in that region. The method further includes moulding a casing on to the first subassembly so that the casing at least partly surrounds the die, the die paddle, and the clip.