Flexfilm – A Novel Film-based MID Process Dr -Ing Marcus Schuck 1 Dr.-Ing. Marcus Schuck Prof. Dr.-Ing. Dietmar Drummer 2 Dipl.-Ing. Andreas Seefried 2 Di l Wi t Dipl.-Wirtsch.-Ing. Michael Fuchs 2 h I Mi h l F h 2 1 Jacob Plastics GmbH Jacob Plastics GmbH 2 Institute of Polymer Technology Institute of Polymer Technology Bergstraße 31 - 35 Am Weichselgarten 9 91489 Wilhelmsdorf 91052 Erlangen D Deutschland / Germany t hl d / G D Deutschland / Germany t hl d / G Tel.: +49 (0)9104 / 8270-492 Tel.: +49 (0)9131 / 85297-00 Fax: +49 (0)9104 / 8270-455 Fax: +49 (0)9131 / 85297-09 m.schuck@jacobplastics.com m.schuck@jacobplastics.com seefried@lkt.uni-erlangen.de seefried@lkt.uni erlangen.de www.jacob-kunststofftechnik.de www.lkt.uni-erlangen.de 1
Content Motivation and Goals – Performance potential Flexfilm Performance potential Flexfilm – Application potential Flexfilm Process chain Flexfilm – Film extrusion – Hot embossing Hot embossing – Radiation cross linking – Thermoforming – Injection molding – SMD assembly Outlook Summary 2
Applications of polymer films Packaging Flexible Decorative films films circuits [Schlenk] Market development flexible circuits Market development flexible circuits market volume example: automobile FFC: flexible flat cables FPC: flexible printed circuits FPC: flexible printed circuits estimated market volume EU 2008: FPC: 300 Mio. € FFC FFC: 1200 Mio. € 1200 Mi € [Freudenberg] 3
Motivation and Goals State of the art 4
Motivation and Goals Performance potential Flexfilm Application of radiation cross linked technical thermoplastics as film thermoplastics as film material for flexible printed circuit boards + three dimensional formability via thermoforming 3D MID 3D-MID (multi layer) + large-area bonding via injection molding 5
Motivation and Goals Application potential Flexfilm Rigid/Flex-Interconnections connector SMD [Lucent] [capicard] Appliction of 2D- Appliction of 2D- Metallization techniques injection molded substrate [Lucent] Multi layer MID (with through connections) conductor path film 6
Basics Radiation cross linking Radiation Cross Linked Non Cross Linked Semi Crystalline Polymer Semi Crystalline Polymer Rubber-elastic Complete Behavior for T > T m Melting for T > T m soldering temperature non cross linked us cross linked ung’s modul radiation cross linked part, radiation cross linked part You non cross linked part, li k d t PA6-GF30, after lead-free PA6-GF30, after lead-free soldering (T max = 255 ° C, 10 min) soldering (T max = 255 ° C, 10 min) RT T g T m 7
Process chain Flexfilm Criteria Adhesion of metallization Thermal expansion Thermoformability Thermoformability Adhesion in injection molding Solderability Solderability One of the central research targets was to find the optimal time for radiation cross linking within the process chain. 8
Film extrusion Film thickness PBT, film extrusion with chill-roll driving speed ess [µm] film thickne pull-off speed [m/min] High quality films with thicknesses from 200 µm to 600 µm can be extruded. 9
Material choice and film extrusion Radiation cross linkable PBT is commercially available and can be extruded to films. Film extrusion of cross linkable, semi crystalline thermoplastics Resin Film extrusion Film PBT V-PTS-Createc-B3HZC Collin ESE E30M (radiation cross linkable) Thickness 300 µm Thickness 300 µm Flat film die 250 ° C Lifocolor COLCOLOR E40/60 Width 220 mm 80 ° C Chill-roll 1 Weight-% Pull off speed Pull-off speed 1.8 m/min 10
Hot embossing Process windows for metallization experimental stamp layout 2 2 1 1 3 0,5 50 peel test p (according to DIN 53494) pull-off speed: 50 mm/min copper strip F Widening of specific hot embossing process window can be reached with polymer film roll ( ∅ 5 mm) radiation cross linking due to enhanced thermo-mechanical resistance. di ti li ki d t h d th h i l i t Peel resistances up to 2.5 N/mm may be detected which are mainly influenced by embossing stamp temperature as key process factor. 30 mm test length 11
Radiation Cross Linking Influence on Mechanical Film Properties Specimen Type 5A Specimen Type 5A Testing climate Testing climate temperature 23 ° C, 50 % rel. humidity Test velocity Test velocity 15 mm/min Tensile Test (according to DIN ISO 527) (according to DIN ISO 527) 12
Metallization and Structuring Radiation cross linkable PBT-films can be metallized with strip lines cost- effectively by hot embossing, fulfilling the demands of high adhesive force at the same time. same time. Hot embossing onto thermoplastic film substrates Film Film (circuit) (radiation cross linkable) 18 µm Copper + BlackOxide Thickness 300 µm + Surface finishing (Tin) Width 220 mm Hot embossing Press system (Blue Tiger Systems) Radiation Embossing temperature 183 ° C cross linking Embossing pressure 33 N/mm² Electron energy 5 MeV Embossing time 0,5 sec Dose 5 x 33kGy 13
Thermoforming Thermoformability of metallization linear draw ratio R l angle α i Thermoforming 1.10 65.4 ° mold geometry 1.15 60.4 ° 1.20 1 20 56 4 ° 56.4 ° 1.25 53.1 ° 1.30 50.3 ° 1.40 45.6 ° metallization 18 µm Cu + BlackOxide elongation increase PBT, 600 µm, 5 x 33 kGy PBT, 600 µm, 5 x 33 kGy painted, without metallization painted, with metallization T U = 230 ° C T U = 230 ° C α i : 56.44 ° , R l = 1.20 α i : 56.44 ° , R l = 1.20 Elongation at break is ca 2 5 % at 200 ° C for the copper foil linear draw ratio in thermoformed parts up to 140 Elongation at break is ca. 2.5 % at 200 C for the copper foil, linear draw ratio in thermoformed parts up to 140 % can be reached with hot embossed films. Due to an elongation increase of the polymer film, greater strains than the copper foil’s elongation at break may be reached by thermoforming metallizied films. 14
Shape Forming and Cutting Thermoforming of PBT-films prior to the radiation cross linking is not possible, but after the cross linking step film substrates featured with necessary forming properties. properties. Thermoforming of metallized film substrates Film (circuit) Film (circuit) Thermoforming Thermoforming Thermoformed insert Thermoformed insert 18 µm Copper + BlackOxide Berg Mini M3 Various deformation degrees Steepest edge 45,6 ° + Surface finish (Tin) Temperature of semi-finished part 240 ° C Dose 5 x 33kGy 40 ° C Mold temperature Mold temperature 40 C Vacuum 15
Injection molding Film adhesion Film material PBT V-PTS-Createc B3HZC Injection molding resin PBT V-PTS-Createc B3HZC Injection molding geometry 16
Injection molding Injection molding - mold Multiple cartridge mold to adjust backmolding geometry to test quality of 1 Adh 1. Adhesion between film and resin and i b t fil d i d 2. Soldering resistance 17
Injection molding Injection molding film + structure Thermoformed insert Injection molding Injection molded Ferromatik Millacron 110t multi-component part Different draw ratios Steepest edge 45.6 ° 295 ° C Steepest edge 45.6 Melt temperature Melt temperature 295 C Injection molded, Injection molded, Mold temperature 80 ° C thermoformed, cross linked film 18
SMD assembly Solderability 19
Outlook Flexfilm Further possibilities for development steps: – Combined use of copper-clad films and subtractive structuring processes – Two-sided metallization with through connection Two sided metallization with through connection – Thermoforming of entire flexible printed circuits – Realization of Rigid/Flex interconnections 20
Summary Flexfilm process With the process chain of Flexfilm three-dimensional interconnect devices can be produced by means of two-dimensional metallization and structuring processes. Thus the Flexfilm process enables the manufacturing of multi layered MIDs. Radiation cross linking may be conducted after film extrusion and has to be carried out at the last after metallization. Extrusion of radiation cross linkable films of technical semi crystalline thermoplastics E t i f di ti li k bl fil f t h i l i t lli th l ti is feasible. By hot embossing copper films onto the polymer substrate good adhesion can be achieved achieved. Thermoformability is greatly increased by radiation cross linking. Due to an elongation increase of the polymer film, greater strains than the copper foil’s elongation at break may be reached by thermoforming metallized films . l ti t b k b h d b th f i t lli d fil Sufficient adhesion to the film insert is achievable by injection molding . The temperature resistance of radiation cross linked films is sufficient for lead-free reflow soldering . f 21
Acknowledgment Our special thanks go to: Bayerisches Staatsministerium für Wirtschaft, Infrastruktur, Verkehr und Technologie for founding this work within the research project NW0707-0008 Entwicklung strahlenvernetzter Flexfolien in project NW0707-0008 „Entwicklung strahlenvernetzter Flexfolien in Hybridgehäusen“ in the program „Neue Werkstoffe in Bayern“ FAPS Institute for Manufacturing Automation and Production Systems , Erlangen, Germany, for their support regarding SMD assembly assembly Beta Gamma Service , Saal a.d. Donau, Germany, for the electron beam irradiation of polymer films 22
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