Warped Die Attach Glue Pattern to Prevent Air Entrapment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Semiconductor devices with warped dies face issues such as air entrapment during die attachment, leading to delamination and performance problems in bonding processes like ribbon wedge bonding, limiting the applicability of conventional stencil printing to thin, small dice.
Innovation Solution
A dual-dispense process combining glue stencil printing and glue nozzle writing creates a central or peripheral raised glue pattern to match the warped die shape, reducing voids and enhancing bonding yield and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If stencil printing is used for die attach material application, then edge bleeding is avoided, but air entrapment occurs due to warped die shape
Solution Approach 1:
The die attach material application is divided into two separate steps: first stencil printing to establish precise material placement, then nozzle writing to add additional material in specific areas. This segmentation allows each step to address specific requirements without compromising the other.
Solution Approach 2:
The stencil printing is performed first to pre-establish the die attach material pattern with precise edges, before the warped die is attached. This preliminary action ensures that the material is correctly positioned, and the subsequent nozzle writing compensates for air entrapment issues.
2Temperature
If reduced die thickness is used, then thermal draining and conduction resistance are improved, but die warpage increases
Solution Approach 1:
The dual-dispense process applies die attach material with different characteristics in different locations: the initially printed material provides base coverage, while the subsequently written material (with different rheology/thixotropy) provides enhanced filling in central or peripheral areas to compensate for warpage-induced air entrapment.
Solution Approach 2:
The process changes the rheological parameters of the die attach material by using different materials or adjusting material properties between the two dispensing steps. This allows the material to adapt to the warped die shape, filling voids and preventing air entrapment while maintaining thermal performance.
3Reliability
If air entrapment is prevented, then delamination is reduced, but process complexity increases
Solution Approach 1:
Two different die attach material application techniques (stencil printing and nozzle writing) are merged into a single integrated process flow. This combination leverages the advantages of both methods: stencil printing provides precision and edge control, while nozzle writing provides flexibility in material placement to prevent air entrapment.
Solution Approach 2:
The dual-dispense process allows the die attach material application to self-adjust to the warped die shape. The second dispensing step automatically compensates for warpage effects without requiring additional external intervention or complex equipment modifications.
Data Source
AI summary
A warped semiconductor die is attached onto a substrate such as a leadframe by dispensing a first mass of die attach material onto an area of the substrate followed by dispensing a second mass of die attach material so that the second mass of die attach material provides a raised formation of die attach material. For instance, the second mass may be deposited centrally of the first mass. The semiconductor die is placed onto the first and second mass of die attach material with its concave/convex shape matching the distribution of the die attach material thus effectively countering undesired entrapment of air.