Teija Laine-Ma, Pekka Ruuskanen, Satu Pasanen and Mikko Karttunen
The aim of this study was to evaluate the feasibility of pad printing for producing electrical conductors and to define the factors affecting the print quality of polymeric silver…
Abstract
Purpose
The aim of this study was to evaluate the feasibility of pad printing for producing electrical conductors and to define the factors affecting the print quality of polymeric silver ink conductors.
Design/methodology/approach
Polyethylene terephthalate (PET) film and polyphenylene oxide (PPO) compound film were used as substrate materials. Three different polymeric silver inks, marked A, B and C, were used and tested.
Findings
The results indicated that the important factors in the pad printing of silver ink conductors are the printing parameters and characteristics of the ink, pad, cliché and substrate. The interactions of these factors should be considered on a case-by-case basis. The sheet resistances of triple-pressed ink conductors varied between 20 and 110 mΩ/sq for 5.7- to 8.5-μm-thick conductors. Ink (B) had a higher sheet resistance than Ink (A) because of its lower silver particle content but also because of the shorter curing time and lower curing temperature. Ink (A) showed excellent adhesion on PET, and Ink (B) had moderate adhesion on PET without corona or plasma pre-treatments, but both inks adhered weakly on PPO compound. Both corona and plasma treatments raised adhesion of these two inks on all test substrates to the highest classification value, 5B.
Originality/value
This paper contains a survey and preliminary testing of the pad printing of polymeric silver ink conductors on flexible thermoplastic foils. Finally, the paper introduces the advantages and drawbacks of the technique.
Details
Keywords
Teija Laine-Ma, Pekka Ruuskanen, Satu Pasanen and Mikko Karttunen
The aim of this study was to test and survey a circuitry transfer technique where conductor patterns are electroformed on carrier substrates and thereafter the electroformed…
Abstract
Purpose
The aim of this study was to test and survey a circuitry transfer technique where conductor patterns are electroformed on carrier substrates and thereafter the electroformed patterns are transferred from carrier substrates to their final devices.
Design/methodology/approach
An electrically conductive pattern is built up by an electrodepositing metal or metal alloy on a carrier substrate, called a mandrel, using a resist image to define the outlines of the pattern. Thereafter, the electroformed structures are bonded on plastic substrates, for instance, by hot pressing or by embedding into a resin. In our experiments, the imaging of stainless steel carriers was done by the photolithographic process and the electroformed copper patterns were transferred by hot pressing onto thermoplastic substrates.
Findings
The literature review revealed that the transfer of electroformed conductor patterns to plastic parts is not a very commonly used technology, although it could provide possibilities for even quite specific structures in electronics manufacturing at an affordable price. Our tests indicated that the acidic peroxide-sulfuric pre-treatment of electroformed copper patterns before hot press bonding clearly improved the adhesion of copper on both acrylonitrile butadiene styrene and polyphenylene oxide substrates and that a steel template around the substrate during hot pressing process can restrict dimensional changes in thermoplastic substrates significantly.
Originality/value
This paper contains a survey and preliminary testing of the electroformed circuitry transfer technique. The analysis of the test boards focused on the adhesion between copper strips and thermoplastic substrates and on the factors affecting adhesion. Finally, the paper introduces the advantages and drawbacks of the technique.