Ink‐Jet Printing,Self‐Assembled Polyelectrolytes,and Electroless Plating: Low Cost Fabrication of Circuits on a Flexible Substrate at Room Temperature

Summary: The driving forces behind the development of flexible electronics are their flexibility, lightweightedness, and potential for low‐cost manufacturing. However, because of physical limitations, traditional thermal processes cause deformations in the flexible substrate. As a result, the adhesion quality of the printed wires is deteriorated. This article reviews recent developments in printing circuits on a flexible substrate by combining self‐assembled polyelectrolytes, ink‐jet printing of a catalyst, and electroless plating of metals. The limitations and potential applications of this technology are also discussed. Experiments implementing this technology demonstrated significant results. By a vibration‐induced assistance during an ink‐jet printing catalyst process, line width and blurring can be controlled to within ±3% variation. Following the IPC 6013 standard for flexible electronics, the results after thermal cycling (288 °C, 6 times) and a hot oil test (260 °C, 3 times) indicated that the metallic circuit had retained excellent adhesion properties and electric characteristics. We also report the first successful demonstration of a metal film in a via‐hole inner wall on a flexible substrate. This novel fabrication method is ideal for the realization of large area, flexible electronics and future multilayer flexible substrate application, such as flexible display, chip on flexible substrate, etc., particularly where traditional lithographic processes can not be applied.

Flexible high‐density circuit on an FR‐4 substrate (left) and picture of via hole with copper inner wall (right).     

Design of novel podand-like compounds with two short diphenylphosphine oxide pendant arms

Crystal and molecular structure of 1,3,5-benzenetris(methylenediphenylphosphine oxide) cyclohexylammonium chloride dibenzene solvate monohydrate has been determined. The overall arrangement of two diphenylphosphine oxide substituents atoms is imposed by intermolecular strong hydrogen bonds, O_(water) H···O_(oxide) and N H···O_{(oxide, water)}. Cyclohexylamine exists in almost ideal chair conformation and nitrogen atom is equatorial to the ring. The structure is build up from strong and weak intermolecular hydrogen bonds to form the three-dimensional infinite hydrogen bond network. Crystal and molecular structure of 1,4-bis[(diphenylphosphineoxide)methyl] - 2,5 - bis (ethoxymethyl) benzene has been determined. The phenyl rings are inclined at 80.91(7)° within the substituent, and they are involved in weak C_(phenyl) H···O_(oxide) hydrogen bonds. The arrangement of diphenylphosphine oxide substituents is imposed practically only by steric effects. Two intramolecular weak hydrogen bonds exist between diphenylphosphine oxide and ethoxymethyl substituents, which can provide additional stabilization to molecule, but it has no noticeable influence on overall molecule geometry. Molecules are assembled via weak intermolecular C H···O_(oxide) hydrogen bonds to the one-dimensional hydrogen-bonded chain along y axis. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:233–240, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20008     

NMR studies of the bishydroxy bisphosphonate synthesis from o‐phthalic aldehyde and diethyl phosphite

The reaction of the o‐phthalic aldehyde with diethyl phosphite leading to the bishydroxy bisphosphonate has been studied. It was found that the reaction is complex and a cyclic acetal formed from the monohydroxyphosphonate is the first relatively stable product. It slowly transforms to the bishydroxy bisphosphonate. The latter compound undergoes intramolecular nucleophilic substitution of the phosphorus atom by the hydroxy group which results in a cyclic structure, a phosphonate‐hydroxyphosphate compound. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:157–164, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10014