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Method for hydrophobic modification of the silica surface to improve the flow properties of capillary underfill with high silica-filler loading

IP.com Disclosure Number: IPCOM000009280D
Publication Date: 2002-Aug-14
Document File: 4 page(s) / 445K

Publishing Venue

The IP.com Prior Art Database

Abstract

Method for hydrophobic modification of the silica surface to improve the flow properties of capillary underfill with high silica-filler loading. Benefits include improved process quality and improved product reliability.

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Method for hydrophobic modification of the silica surface to improve the flow properties of capillary underfill with high silica-filler loading

Method for hydrophobic modification of the silica surface to improve the flow properties of capillary underfill with high silica-filler loading. Benefits include improved process quality and improved product reliability.

Background

� � � � � The flow performance of the underfill material is reduced when more than 65% of the silica filler is loaded into the material. Filler content higher than the stated amount cannot be added to reduce the coefficient of thermal expansion of the underfill materials. Fillet cracking and delamination of underfill materials occur due to thermal mismatch. Increasing the filler content reduces the moisture absorption of the package and lowers the coefficient of thermal expansion (CTE), making the component 260°C high-temperature reflow compatible.

� � � � � Increasing the hydrophobic surface of the silica conventionally reduces the affinity of the capillary underfill materials to moisture, reducing the moisture absorption of the material.

        � � � � � The hydrophobic surface of the silica conventionally improves the flow of the underfill material because of compatibility with the substrate surface. Insufficient die edge coverage is reduced and package reliability is improved.

        � � � � � Conventionally, the thixotropic index of the materials is reduced. Materials that have high hydrogen bonding have a high thixotropic index. This characteristic reduces the ability of liquid underfill to flow.

General description

        � � � � � The disclosed method is the modification of silica surfaces with hydrophobic groups. They include:

·        Alkyl

·        Alkene

·        Alkyne

·        Heterocyclic or aromatic (benzyl/naphthyl) groups

        � � � � � This method reduces the bonding effect between silica particles that reduces its ability to flow. As a result, the underfill material’s viscosity and flow properties are improved. More fillers can be loaded into the underfill materials and results in a lower coefficient of thermal expansion on the underfill materials. The hydrophobic groups disrupt the hydrogen bonding effect and provide a coating to the filler. As a result, flow increases.

 


Advantages

        � � � � � The disclosed method provides advantages, including:

·        High loading of silica fillers without reducing the flow performance of capillary underfill

·        Improved reliability of flip chip packages due to reduced CTE

·        Improved flow performance of the underfill materials is increased

·        Improved adhesion of the epoxy t...