Flip chip

Recently commercially available X-ray systems for laminography have a spatial resolution limited to hundred microns, which is not enough for modem multilayer electronic devices and assembles. Modem PCBs, flip-chips, BGA-connections etc. can contain contacts and soldering points of 10 to 20 microns. The classical approach for industrial laminography in electronic applications is shown in Fig.2. 

Fig. 5. Various layers in a flip-chip bond, where BLM = ball-limiting metallurgy and TSM = top-surface metallurgy (3).

The most widely used high melting point solder for flip-chip bonding is 95% lead—5% tin solder (mp C) eutectic 60% lead—40% tin solder... 

Baggerman, A. Schwarzbach, D. 1998. Solder-jetted eutectic PbSn bumps for flip-chip. IEEE Transactions on Components Packaging and Manufacturing Technology Part B-Adv. Packaging 21 371-381. 

The adhesives are suitable for use in flip chip bonding of semiconductor parts. They exhibit good shelf stability, productivity, strength properties and heat resistance. The electrical properties, such as dielectric constant and dielectric loss tangent are highly satisfactory. 

For chips that are flip-chip bonded, additional conductor layers may be required to redistribute the I/Os from underneath the chip to the engi-... 

The most advanced implementation of cofired-ceramic-packaging technology is the thermal conduction module (TCM) used in large-scale computers (IBM) (4, 72, 74). This package can accommodate over 100 flip-chip-bonded ICs on a 90 by 90 mm cofired ceramic substrate. The multilayer ceramic substrate contains 33 metal layers for chip pad redistribution, signal interconnection, and power distribution (Figure 14). Each chip contains 120 bonding pads, and 1800 pins are brazed to the bottom of the substrate for connection to a PWB. 

Novel Approaches. A number of groups have focused on silicon substrates for thin-film interconnections (89, 91-93, 97). The most advanced technology of this type is AT T s advanced VLSI package (AVP), which uses flip-chip solder bonding of ICs onto a silicon substrate containing high-... 

Murine embrionic stem cells Bio Flip Chip 2007 [170]... 

The photodiodes of the imagers presented in US-A-4566024 are formed in a p-type HgCdTe substrate by diffusing n-type impurities from two opposite faces, a front face and a rear free, of the substrate. The photodiodes can be connected to a read-out device by a flip-chip bonding process on the rear face of the substrate and still be illuminated from its front free. 

A process to manufacture an imager is disclosed in JP-A-63260171. Photodiodes, formed in HgCdTe chips, are tested before they are mounted on a temporary substrate. The chips are further treated before they are bonded to a CCD with a flip-chip bonding process. 

The invention of GB-A-2246662 refers to testing of an imager by the use of a test element group. Elements of the test element group are connected by indium bumps to connection pads on a read-out substrate in the same flip-chip bonding process which connects detector elements to the read-out substrate. 

The problem of cross-talk between adjacent photodiodes and the problem of different thermal expansion coefficients between a silicon substrate and an HgCdTe substrate are approached in JP-A-63281460. A detector is made up of HgCdTe wells, comprising photodiodes, formed in a CdTe substrate. The detector is bonded to a silicon substrate by a flip-chip process, and finally the CdTe substrate is etched away. 

The problem of cross-talk between adjacent photodiodes is solved in JP-A-2303160 by forming islands of HgCdTe, comprising photodiodes, on a CdTe substrate and then bonding them to a read-out device by a flip-chip bonding process. 

An HgCdTe layer 2, comprising photodiodes 3, is formed on a first side of a CdTe substrate 11. The detector is bonded to a silicon chip 7 by a flip-chip process. A reflection preventive film is formed on a second side, opposite to the first side, of the CdTe substrate. The film is formed by a cyclotron resonance plasma CVD method by introducing nitrogen, nitrous oxide and silane as reaction gas. The thickness of the film is selected so that the reflectivity is minimized for radiation having a wavelength to be detected by the photodiodes. 

Finally, the exposed photodiodes are connected to a CCD by the use of connection bumps in a flip-chip process. 

HgCdTe wells S, comprising photodiodes 7, are formed in a CdTe substrate 1. The anodes and cathodes of the photodiodes are connected by indium columns 12 and 13 to a silicon substrate 9 by a flip-chip bonding process. 

P-type HgCdTe well regions 5 are formed in a CdTe substrate 1. Photodiodes are created by forming n-type regions in the p-type wells. The p-type well regions 5 are connected to each other by an Au film 21 forming a common electrode. The n-type regions are connected to input diodes 10 prepared in a silicon substrate 9 by indium columns 12 in a flip-chip process. The space between the CdTe substrate and the silicon substrate is filled with an epoxy resin 22. 

Flip-chip arrangements for connecting a mercury cadmium telluride chip to a read-out chip are presented in this chapter. 

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