Pre-Printed Adhesive on Lead Frame for Semiconductor Packaging
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Solution Overview
Problem
Existing semiconductor packaging methods face issues such as adhesive material overflow, uneven thickness, high stress on chips, oxidation of lead frames, and reduced conductivity and productivity due to the use of soldering paste or epoxy resin in chip adherence processes.
Innovation Solution
The method involves pre-printing adhesive material on the lead frame and chip carrier using stencil or screen technology, allowing for precise control of adhesive thickness and size, and using printable epoxy resin for improved conductivity and reduced stress, which is then cured at lower temperatures to enhance chip adherence and packaging efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If adhesive material is dispensed onto the chip carrier by adhesive injection, then chip adherence is achieved, but adhesive material overflows around the chip which limits the chip size to be smaller than the chip carrier size
Solution Approach 1:
The adhesive material is pre-printed on the chip carrier in specific patterns (such as rings or dots) at defined positions before chip placement. This preliminary action ensures that adhesive is only present where needed, preventing overflow while maximizing the usable chip area on the carrier.
Solution Approach 2:
Instead of applying adhesive uniformly across the entire chip carrier surface, the invention applies adhesive material locally at specific zones where the chip will contact the carrier. This localized application prevents unnecessary adhesive overflow while ensuring adequate bonding at the chip-carrier interface.
2Shape
If adhesive material is formed by adhesive injection, then chip adherence is achieved, but the formed adhesive material is uneven in thickness causing chip inclination
Solution Approach 1:
The adhesive material is pre-printed on the chip carrier with controlled thickness and uniform distribution in specific patterns before chip placement. This preliminary action ensures that when the chip is placed, it contacts a uniformly thick adhesive layer, preventing chip inclination while simplifying the placement operation.
3Strength
If soldering paste or epoxy resin is used as adhesive material, then chip adherence is achieved, but very high stress is produced likely to cause chip cracking
Solution Approach 1:
The invention changes the material parameters by using printable epoxy resin with specific rheological properties that allow it to be printed in controlled patterns. This resin formulation provides adequate bonding strength while reducing the stress transmitted to the chip, preventing cracking while maintaining attachment strength.
4Manufacturing precision
If adhesive injection is used to form epoxy resin, then chip adherence is achieved, but the epoxy resin thickness is hard to control and tends to be thicker than necessary leading to higher resistance
Solution Approach 1:
The adhesive material is pre-printed on the chip carrier with precisely controlled thickness using printing technology. This preliminary action ensures that the adhesive layer is uniformly thin where needed, minimizing the resistance between the chip and carrier while preventing overflow. The printing process allows precise control of material deposition thickness.
5Reliability
If adhesive injection is used for chip adherence, then chip attachment is achieved, but offline high temperature curing is required which greatly impairs production line efficiency
Solution Approach 1:
The invention merges the adhesive application and curing processes by using printable epoxy resin that can be applied and cured in an integrated manner. The resin is printed in controlled patterns and then cured using inline heating methods, combining material deposition and curing into a more streamlined process that improves production efficiency while ensuring complete curing.
Solution Approach 2:
The invention replaces the traditional offline curing process with inline curing methods, substituting a separate mechanical curing step with an integrated thermal processing approach. This allows curing to occur during the same production cycle as adhesive application, eliminating downtime and improving overall productivity.
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 prevents adhesive overflow, ensures even chip adherence, reduces chip cracking, maintains high electrical and thermal conductivity, and improves production efficiency by eliminating the need for post-adhesion cleaning and offline curing, thereby enhancing the quality and productivity of semiconductor packages.
Implementation Method 1
using printable epoxy resin for improved conductivity and reduced stress, which is then cured at lower temperatures to enhance chip adherence
Data Source
AI summary
This invention discloses a semiconductor package with adhesive material pre-printed on the lead frame and chip, and the manufacturing method. The adhesive material is applied onto the chip carrier and the pin of the lead frame and also on the front electrode of the semiconductor chip via pre-printing. The back of the semiconductor chip is adhered on the chip carrier, and the front electrode of the semiconductor chip and the pin are connected respectively with a metal connector. The size, shape and thickness of the adhesive material are applied according to different application requirements according to size and shapes of the contact zone of the semiconductor chip and the metal connector. Particularly, the adhesive zones are formed by pre-printing the adhesive material thus significantly enhance the quality and performance of semiconductor products, and improves the productivity.