(A) study on fabrication of the glass circuit board (GCB) and its ultra-fine pitch flip chip assembly using non-conductive films (NCFs)

Abstract

As the fastest growing recent smartphone market in industries, the industries for electronic materials and components of mobile information technology equipment such as a portable display and multimedia capabilities have been made rapid growth. Accordingly, the semiconductor components of the mobile devices are required of multi-functional, integration, miniaturization, and lower power properties. This situation has led to increasing demand for semiconductor packaging technology of the new scheme with the high integration of a semiconductor transistor technology. Flip-chip module package using a 'Through Silicon Via (TSV)' that has started commercialization recently can be said that a representative example. Flip-chip bonding technology was already developed by IBM in 1960s. Especially the TSV & micro bump can vertically stack up the flip chips. In terms of the technical trend to the fine pitch scale, bonding method of copper pillar bumps of the application processor & the baseband & the central processing unit & the graphics processing unit is changed from the C2 (chip connection) reflow soldering technic to the thermal compression method in 2014. With this approach, it is possible to form reliable solder joints in a fine pitch. Because bonding can be proceeded by using the non-conductive adhesive film including the potential flux. The curing agent in film can be ensured to high room temperature storage stability, high temperature stability, insulation by using an acid anhydride series. Anhydride NCF can have potential flux properties at a particular temperature and starts acid and curing reaction at this temperature. For a flip-chip module substrate, there is adopted a thin core technology being expanded to reduce the thickness of the substrate to the current trends according to smaller and lighter implementation. However, the flip-chip module of the mobile device that has a large spatial limitation has a warpage characteristic problem due to the thermal expansion coefficient difference between the silicon chip and the organic substrate. So, the glass is required as a core material to improve warpage characteristic instead of copper clad laminate. And this glass has smaller warpage property with 50GPa or more elastic modulus. Thermal expansion coefficient of silicon or glass is lower than organic material. So this property has the advantage of fine pitch process and electrical characteristic. And the glass interposer is currently developing for applied to the 2.5D system in package (SiP). However the glass which is not processed by special treatment may be breakage in the specific situation, if it is handled without coating protection. In this thesis, we handle a ‘Glass Circuit Board (GCB)’ which complements this problem. GCB has a same multi layered structure of conventional ‘Printed Circuit Board (PCB)’ and advantages of the glass interposer. However ‘Through Glass via (TGV)’ formation and copper filling in TGV is the most difficult process to process glass circuit board. And we need to know the assurance methodology of quality and reliability of the module made. Currently, the circuit board is downsizing for small form factor of product. Area miniaturization of passives like capacitor, inductor, and resistor for noise filtering at high frequency is needed. So, the embedded passive technique is required for integration in the substrate. And we embedded the high-k capacitor in GCB using this technique. In this thesis, we study two experimental parts. In the first part, we develop the processes of the Glass Circuit Board (GCB) and its units. We firstly study the copper filling process in TGV. It is core technology for fabrication of GCB. And then we study its electrical characteristic. We study fabrication process and electrical characteristics of high-k MIM capacitor on glass substrate as embedded passives. We lastly study fabrication process of GCB and compare warpage property between conventional flip chip module and GCB module using computing simulation tool. In the second part, we study characterization and reliability of ultra-fine pitch flip chip assembly using NCFs. We firstly study optimized flip chip bonding condition based on parallel plate model equation for stable interconnection between ultra-fine pitch flip chip and substrate. We split the filler contents of non-conductive film including the potential flux component and then study the change of viscosity and elastic modulus of film by the effects of filler contents. Finally, we study the effects of these at long term reliability testing of ultra-fine pitch flip chip module.