Die Paddle Recesses for Uniform Solder Bond Line Thickness
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Solution Overview
Problem
The challenge of achieving uniform bond line thickness (BLT) in semiconductor devices is exacerbated by die movement during the DACA and reflow processes, leading to non-uniform solder joints and die tilting, which can result in strain concentration, solder voids, and potential die cracking.
Innovation Solution
Incorporating recesses in the die paddle surface to receive and embed spacers, allowing for even distribution of spacers under the die, thereby maintaining uniform solder BLT and preventing die tilting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If spacers are used to maintain uniform bond line thickness, then solder joint uniformity is improved, but spacer distribution unevenness causes die tilting and strain concentration
Solution Approach 1:
The die paddle surface is segmented into multiple recesses distributed across the bonding area. Each recess individually captures and positions a spacer, ensuring uniform spacer distribution. This segmentation approach prevents spacer clustering and eliminates die tilting while maintaining consistent bond line thickness throughout the large die area.
Solution Approach 2:
Recesses are pre-formed on the die paddle surface before the soldering process. These recesses preliminarily position the spacers in predetermined locations, ensuring uniform distribution before the actual bonding occurs. This preliminary action prevents spacer migration and ensures reliable die attachment from the start.
2Reliability
If larger die are used to achieve superior RDSON performance, then device performance is improved, but achieving uniform bond line thickness becomes increasingly difficult
Solution Approach 1:
For large die areas, the surface is divided into multiple recesses strategically distributed across the entire bonding region. This segmentation ensures that spacers are uniformly positioned throughout the large area, maintaining consistent bond line thickness even across extended die dimensions used for high-performance applications.
Solution Approach 2:
Recesses are locally distributed across different regions of the die paddle surface based on specific bonding requirements. This local quality approach ensures optimal spacer positioning in each region of the large die, maintaining uniform bond line thickness throughout the entire bonding area regardless of die size.
3Ease of manufacture
If molten solder is used to attach the die, then bonding is facilitated, but solder may not be strong enough to prevent die movement during DACA and reflow processes
Solution Approach 1:
Recesses are pre-formed on the die paddle surface to preliminarily position and constrain spacers before the soldering process. This preliminary action ensures that spacers remain in fixed positions during DACA and reflow, preventing die movement while still allowing the molten solder to flow and bond effectively.
Solution Approach 2:
Spacers act as intermediary elements between the die paddle and the die. Positioned within recesses, these spacers serve as stable reference points that prevent die movement during soldering, while still allowing the molten solder to flow around them and create strong bonds.
4Productivity
If vaporized solvent in the solder moves the die during reflow, then soldering process is completed, but non-uniform bond line thickness and die tilt occur
Solution Approach 1:
Recesses are pre-formed to preliminarily position spacers in fixed locations before reflow. This preliminary positioning ensures that even when vaporized solvent causes movement during reflow, the spacers remain constrained within recesses, maintaining uniform bond line thickness throughout the soldering process.
Solution Approach 2:
The recesses provide preliminary anti-action against die movement caused by vaporized solvent during reflow. By constraining spacers within recesses before the harmful effect occurs, the design prevents the solvent vapor from displacing spacers and causing non-uniform bonding.
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 solution ensures consistent solder BLT, reduces the risk of solder voids and die cracking, and enhances the reliability of semiconductor devices by evenly distributing spacers, thus improving thermo-mechanical stress resistance.
Implementation Method 1
heating the solder paste or solder preforms applied to the bonding pads of the components and the corresponding contact areas on the substrate to a temperature where the solder transitions from a solid to a liquid state
Implementation Method 2
the die paddle comprises a plurality of recesses in the upper surface of the die paddle, wherein the plurality of recesses is configured for receiving the plurality of spacers, such that the plurality of spacers is embedded within the plurality of recesses
Data Source
Figure 1~2
Figure 3A
Figure 3B
AI summary
A semiconductor device comprising: a die paddle having an upper surface; a solder layer disposed on the upper surface of the die paddle; and a die disposed on the solder layer, such that the solder layer is between the die paddle and the die; wherein the solder layer comprises a plurality of spacers configured to be, during production of the semiconductor device prior to hardening of the solder layer, movable in relation to the die paddle; and wherein the die paddle comprises a plurality of recesses in the upper surface of the die paddle, wherein the plurality of recesses is configured for receiving the plurality of spacers, such that the plurality of spacers is embedded within the plurality of recesses