Yoshihiro Bessho

A Stud-bump-bonding Technique For High Density Multi-chip-module

technique for high density Multi-Chip-Module (MCM), using called Stud-Bump-Bonding (SBB) technique, which can bond bare LSI chips directly to ceramic substrate. Au bump is formed on electrode pad of LSI chip by a wirebonding apparatus. Each Au bump has two-stepped construction and bonded with a conductive adhesive to an electrode terminal formed on the ceramic substrate. The conductive adhesive is very flexible and strong in bond, thus resisting thermal and mechanical stresses. Moreover, repair technique has been developed. 100 ,u m pitch electrode pads of LSI chip can be bonded to electrode terminals. The bonding resistance is less than 50 m i l . memory module. High density and reliability in bonding for MCM have been attained by the SBB technique. We have developed advanced flip-chip bonding We have applied the SBB technique to high density MCM for

Development of chip-on-flex using SBB flip-chip technology

Abstract A bare LSI chip mounted onto a flexible substrate is called chip-on-flex (COF). Companies and universities are desperately developing COF. In this paper, the development of COF using stud bump bonding (SBB) flip-chip technology will be introduced. So far, SBB technology has been adopted when ceramic or glass-epoxy is used as a substrate material for chip size packages (CSPs) and multi-chip modules (MCMs). Recently there is a great demand for developing SBB technology toward a flexible substrate. SBB technology needs to keep a flexible substrate flat during the assembly process. A flexible substrate was adhered to a flat carrier using a thermal release sheet in order to keep it flat. Since this thermal release sheet loses its adhesive strength by applying heat beyond 160°C, it is easy to peel off accomplished specimens from the flat carrier after assembling. SBB specimens were prepared using liquid crystal polymer (LCP) and polyimide (PI) as a flexible substrate. Reliability tests, such as pressure cooker test (PCT), thermal shock test (TST) and reflow soldering after moisture storage test, were carried out for these specimens. In PCT, both LCP and PI specimens passed as a result of using proper underfill for each substrate. In TST, both specimens also passed using the underfill selected in PCT. In reflow soldering after moisture storage test, LCP specimens passed, on the other hand PI specimens needed to be baked after moisture storage in order to pass the reflow.

Packaging properties of ALIVH-CSP using SBB flip-chip bonding technology

A new chip scale package (CSP) using an organic laminated substrate (CSP-L) was developed, which was fabricated using an ALIVH (any layer inner via hole) substrate as an interposer and stud-bump-bonding (SBB) flip-chip technology. The ALIVH substrate is a multilayered organic substrate with inner via holes in any layer. The newly developed CSP-L using the ALIVH substrate realized package size miniaturization on the same scale as a CSP using a ceramic substrate (CSP-C). The SBB flip-chip bonding on the ALIVH substrate required an excellent substrate surface coplanarity. The required coplanarity was obtained using a fixture during the SBB flip-chip bonding process. The first-level packaging reliability and the second-level packaging reliability on a glass-epoxy motherboard were evaluated. The resulting reliabilities were good enough for practical applications.

Advanced MCM-Ls for consumer electronics

We have developed an advanced MCM (multichip module) using the SBB/sup TM/ (stud-bump bonding) flip-chip technique on an ALIVH/sup TM/ (any layer inner via hole) structure substrate. The SBB technique is an advanced flip-chip bonding technique for high density MCM, which can mount bare LSI chips directly on substrates. The bonding portion structure is composed of Au bumps with two-stepped construction and conductive adhesives. The conductive adhesive is very flexible in bond, thus relaxing thermal and mechanical stresses. The ALIVH substrate is a high density and high performance multilayered printed wiring board with any layer inner via hole structure, CO/sub 2/ laser via hole processing technology and interconnection technology which employs conductive paste. We had good results for several reliability tests in the advanced MCM-L test vehicles. In particular, in the thermal shock test, the increase in connection resistance in the advanced MCM-Ls was smaller than that of MCM-Ls which used ordinary organic substrates instead of the ALIVH substrate. We manufactured a CCD camera module using these MCM-Ls. LSI chips were mounted on the six-layered ALIVH substrate. The MCM-Ls obtained was downsized (60% down) and lighter in weight (30% reduction) when compared with the conventional module, and the electrical characteristics of the newly manufactured CCD camera module were equal to those of the conventional module.

A 1.5 Ghz-band Saw Filter Using Flip-chip-bonding Technique

We applied a stud-bump-bonding (SBB) technique which is a kind of flip-chip-bonding (FCB) technique to a l.5GHz-band surface acoustic wave (SAW) filter. The SAW filter mounted by the SBB technique showed almost the same frequency characteristics as that mounted by a conventional wire-bonding technique at 1.5GHz. Using the SBB technique, the area of the SAW filter became 115 comparing with conventional SAW filters mounted by the wire-bonding technique and the weight became less than 1/10 by the share of the package. The SBB technique has; a lot of potential to reduce the size and weight and to realize small and high performance modules even above GHz frequencies.

A zero X-Y shrinkage low temperature cofired ceramic substrate using Ag and AgPd conductors for flip-chip bonding

A zero X-Y shrinkage low temperature cofired ceramic (LTCC) substrate was developed, that was applied to the flip-chip bonded chip-size-packages (CSPs) and multi-chip modules (MCMs). The Ag internal conductor,the AgPd external conductor and the newly developed Ag via conductor could be used by matching the sintering shrinkage behavior with that of the zero X-Y shrinkage LTCC substrate. The flip-chip bonding using stud-bump-bonding (SBB) technique could be performed onto the external conductor of this developed substrate without Au plating and stable flip-chip bendability was obtained.