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J. Maattanen
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ABSTRACT: Anisotropically conductive adhesives (ACA) are becoming more and more popular in electronic device high density interconnections. The main application areas for ACA are in the attachment of flip chip on glass (COG), flip chip on flex (COF) and TCP (tape carrier package)-flex on displays. The understanding of the conduction mechanisms for anisotropically conductive adhesives is of vital importance when choosing the right adhesive for a specific application. In the conductivity model, a formula has been created that can be used to estimate how the degree of deformation of the particles affects the resistance, especially in the case of soft metal-coated polymer particles. Since the particle resistance is only a part of the total contact resistance, the model has to take into account the interface resistances between the different materials. Using this model, it is possible to calculate an estimate of the total contact resistance. Some comparisons are made with real measurements to verify the model.
Electronic Packaging Technology Proceedings, 2003. ICEPT 2003. Fifth International Conference on; 11/2003
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ABSTRACT: This paper presents results from an extensive reliability test program on high-density flip chip assemblies on flexible substrates. The test program included thermal cycling, high temperature, hot humidity and pressure cooker tests. In this reliability test, four different kinds of substrates were used: polyimide, polyester and epoxy glass with 80 μm pitch and upilex with 54 μm pitch. Two different layouts of the bond pads were designed, peripheral and staggered, and chip and flex were assembled using thermosetting anisotropic conductive adhesive film. The test samples were measured electrically using a four-point method for the contact resistance and a daisy chain for the overall yield of the contacts. Afterwards cross sections were made to determine the reason of the failures. This work was carried out in the frame of the European Union funded IST project "FLEXIL".
Electronics Technology: Integrated Management of Electronic Materials Production, 2003. 26th International Spring Seminar on; 06/2003
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ABSTRACT: The paper investigates the possibilities to flip-chip assemble Si driver chips onto a flexible display, which is to be integrated in a smart card. The chips are Au or Ni/Au bumped, the substrate material consists of PES (polyether sulphone) with conductive ITO pads. One technology, using ICA and NCA seems to be quite straightforward, another, using ACA, reveals the problem of ITO damage during thermocompression.
Polymers and Adhesives in Microelectronics and Photonics, 2002. POLYTRONIC 2002. 2nd International IEEE Conference on; 02/2002
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ABSTRACT: Lighter, smaller, faster and cheaper are the magic words used to describe the trends in modern electronics. The miniaturization is a must in the market of the portable devices. Beside of the mobile phones there are several other application areas like smart cards, smart cloths, portable minicomputers, cameras, entertainment electronics and so on. The big challenge is to find the most effective technology to produce all those devices with competitive prices. The key factor is the interconnection technology. The environmental factors like lead and halogen free production are other challenges that must be taken into account This paper presents the development of fine pitch (54 μm) flip chip on flex (FCOF) interconnection. There are several factors affecting to the reliability of the high density interconnection like the flex material, the bumping of the test chips, the bonding equipment and the anisotropically conductive adhesive used to make the connection. During the development phase it was noticed that by a careful testing and by making right selections it is possible to find working combination of materials and processes for high density interconnection. To insure the reliability, the samples were tested using thermal shock tests (-40C&rlhar2;+125C) and 85C/85R.H. humidity test. Cross section samples were made to analyze the possible failure mechanism of failed contacts. Two different types of test devices were used. The contact resistance was measured with four-point method and the series resistance with Daisy chain method. The results area part of development project supported by European Union.
Polymers and Adhesives in Microelectronics and Photonics, 2002. POLYTRONIC 2002. 2nd International IEEE Conference on; 02/2002
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ABSTRACT: This paper presents the latest results from the reliability tests
of high density flip chip on flex application using anisotropically
conductive adhesives. Four different types of flexible substrates and
two different types of anisotropically conductive adhesives were
selected. Both paste and film type anisotropically conductive adhesives
were used. Two different test devices were used. The contact areas were
50×50 μm and 50×90 μm. The effective pitch was 80
μm in both samples and the number of contacts was 200. The matrix of
both anisotropically conductive adhesives was epoxy based and the
conductive particles in film type were isolated soft metal-coated
polymer particles and in paste type isolated silver particles. The
contact resistance was measured with a four-point method and the series
resistance with a daisy chain method. The reliability of the flip chip
interconnections was tested in thermal cycling tests. Cross section
samples were made to analyze the possible failure mechanism of failed
contacts
Polymers and Adhesives in Microelectronics and Photonics, 2001. First International IEEE Conference on; 02/2001
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ABSTRACT: In the portable electronics product business, there is a strong
trend towards miniaturization. At the same time, when the size and the
weight of these products are decreasing, the number of functions and the
performance is increasing. This trend towards miniaturization means that
the packaging density is increasing significantly. The target of our
research was to develop a small pitch flip chip on flex process for
electronic module applications. This paper presents the results from the
reliability tests of different types of flexible substrates and
different types of anisotropically conductive adhesives in high-density
flip chip application. The reliability of the samples was tested using
thermal shock tests and 85/85 tests. Cross section samples were made to
analyze the possible failure mechanism of failed contacts. Two different
test devices were used (bump sizes 50×50 μm and 50×90
μm). The effective pitch was 80 μm in both samples and the number
of contacts was around 200. The contact resistance was measured with the
four-point method and the series resistance with the daisy chain method.
The results are part of a European Union supported development project
Electronic Materials and Packaging, 2001. EMAP 2001. Advances in; 02/2001
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ABSTRACT: Applicability of no-flow fluxing encapsulants and flip chip
technology in volume production was studied. Adhesion of the underfill
materials to different solder resists was measured with single lap shear
test and the results compared with traditional underfills. No-flow
underfiller was dispensed with standard in line dispenser. SnPb-bumped
flip chip test structures were pick and placed on FR4 substrates by
using standard volume production line. The bump pitch of the test chips
was 250 μm. Sample boards were also precured in standard production
oven and postcured in baking oven. No-flow underfillers showed
exceptionally good adhesion to used solder resists. With the no-flow
underfillers flip chip proved to be transparent to the current SMA
process, however the process window for dispensing and reflowing is
relatively narrow
Adhesive Joining and Coating Technology in Electronics Manufacturing, 2000. Proceedings. 4th International Conference on; 02/2000
