Plasma-treated polyimide

Q < 50°) for 12 months. The aging effect is illustrated in Fig. 9-28 for the case of plasma-treated polyimide fluoroplastic film. As one can see from the figure, restoration of the wettability contact angle 0 takes place mostly during the first 10 days, and then the aging process slows down. 

Fig. 13.2 The forward recoiled spectrum of H and from He ions incident with energy 2.18 MeVon a thin deut-erated polyimid film (a) and with energy 2.75 MeV on D-plasma treated LiNbOj (b). 

Fig. 7. C(ls) XPS spectra for MW and MW-RF Nj plasma treated polyethylene (left column) and Kapton polyimide (right column). (Modified after ref. 21).

Widely used substrate materials include poly(ethylene naphthalate) and poly(ethylene terephthalate) of thickness 25-75 )im. A cheap commercial source of poly(ethylene terephthalate) is laser inkjet transparency film. Interestingly, both PEN and PET can withstand temperatures up to 180—220 C. PEN also has the advantage that it is about three times less permeable to water and oxygen than PET. Other widely used substrate materials include polycarbonate, polyimide, and PEEK. Some commercial plastic films are also obtainable with oxygen plasma-treated poly(urethane) primer layers on one side, to raise the surface energy and thereby improve the adhesion of inks. 

DYCOstrate. A different approach to small via creation has been taken by Dyconex AG of Switzerland. After ground and power patterns are formed on the panel, and the panel is oxide-treated, polyimide-backed copper foil is laminated on the panel. Holes in the copper are formed by a chemical etching process, and the insulating polyimide material underneath the holes is removed by plasma etching. PWBs made in such a way are called DYCOstrate. In other, similar technologies, different dielectric materials are used, and they are removed by alkaUne solutions. The rest of the process is similar to that for SLC that is, holes are metallized and a thick copper deposition is made by electroless or galvanic plating, and the circuit pattern is formed by a tent-and-etch process (see Fig. 5.5). 

Fig. 28. Proposed mechanism for reaction of copper with PMDA/ODA polyimide that was treated in an oxygen plasma for 1 s. Reproduced by permission of John Wiley and Sons from Ref. [33].

Several commercial polymers (polyethylene, polyimide, polytetrafluoroethylene, polyvinylchloride and polycarbonate) have been treated by low temperature glow discharge plasmas in various gases, namely NH3, 02, Ar, and CF4. 

Sample Preparation. PMDA-ODA polyimide films were prepared by spin coating polyamic acid onto silicon wafers and curing to 360°C for 1 hour. The cured film thickness was approximately 10 pm. These samples were treated downstream of an 85% CFi -15% 02 microwave plasma for 30 minutes to produce a fluorinated layer, approximately 600 thick (16). Fluorinated layers less than 600 thick were obtained by additional treatment downstream from an 02 rich (85%) microwave plasma for various times. PTFE films (25 pm thick) were used as received from E. I. duPont de Nemours Inc. 

Figures 4a and 4b show the C Is and F Is regions, respectively, for a polyimide film treated in a CF rich plasma for 30 minutes.

Substrates used included fiber-reinforced epoxy base polymer [FRP], nylon 66, polytetrafluoroethylene [Teflon], poly(ethylene terephthalate) [PET], phenolic resin, and thermoplastic polyimide [ULTEM, GE]. FRPs were the primary substrates used. Initially, they were cleaned with detergent in an ultrasonic bath followed by rinsing with deionized water and alcohol. For further cleaning, they were treated with oxygen plasma (1.33 seem, 60 W, 5 min) followed by a hydrogen plasma treatment (3 seem, 60 W, 5 min). 

Figure 9-28. Typical dependence of water contact angle (0) on storage time in normal air conditions. Plasma-modified film (1) laminated polyimide fluoroplast film treated in air plasma 50 Hz (2) TFE fluoroplast.

In both types of continuous systems the maximum processing speed ( line speed ) is determined by the required residence time in the plasma to get the proper treatment. The present data show that, for reasonable power densities and existing equipment, clean polymers (e.g. polyethylene, polyimide, and polyamide) can be treated in less than 10 seconds residence time. This gives a line speed of 150 m/min (500 ft/min) or more. 

Kim Soo Hong, Cho Su Hyeun, Lee Nae-Eung, Kim Hoon Mo, Nam Yun Woo, and Kim Young-Ho. Adhesion properties of Cu/Cr films on polyimide substrate treated by dielectric barrier discharge plasma. Surf. Coat. Tech. 193 no. 1-3 (2005) 101-106. 

Polyimide and polyimide-acryhc systems are processed in chromic acid or plasma.Teflon , and R T Duroid materials are treated (before operations) in sodium-naphthalene mixtures to yield void-free, high-bond-strength copper in the PTH.The introduction of lead-free material and halogen-free material has challenged the desmear processes. The new materials are more chemically resistant, and thus more aggressive desmear cycles are required to remove any smear. These more chemically resistant resin systems are more difficult to texture. Alternative solvents, higher temperatures, and cycle optimization may be required to process these newer materials effectively. 

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