Flexfilm A Novel Film-based MID Process

Transcription

1 Flexfilm A Novel Film-based MID Process Dr.-Ing. Marcus Schuck 1 Prof. Dr.-Ing. Dietmar Drummer 2 Dipl.-Ing. Andreas Seefried 2 Dipl.-Wirtsch.-Ing. Michael Fuchs 2 1 Jacob Plastics GmbH 2 Institute of Polymer Technology Bergstraße Wilhelmsdorf Deutschland / Germany Tel.: +49 (0)9104 / Fax: +49 (0)9104 / m.schuck@jacobplastics.com Am Weichselgarten Erlangen Deutschland / Germany Tel.: +49 (0)9131 / Fax: +49 (0)9131 / seefried@lkt.uni-erlangen.de erlangen.de 1

2 Content Motivation and Goals Performance potential Flexfilm Application potential Flexfilm Process chain Flexfilm Film extrusion Hot embossing Radiation cross linking Thermoforming Injection molding SMD assembly Outlook Summary 2

3 Applications of polymer films Packaging films Decorative films Flexible circuits [Schlenk] market volume Market development flexible circuits example: automobile FFC: flexible flat cables FPC: flexible printed circuits estimated market volume EU 2008: FPC: 300 Mio. FFC: 1200 Mio. [Freudenberg] 3

4 Motivation and Goals State of the art 4

5 Motivation and Goals Performance potential Flexfilm Application of radiation cross linked technical thermoplastics as film material for flexible printed circuit boards + + three dimensional formability via thermoforming large-area bonding via injection molding 3D-MID (multi layer) 5

6 Motivation and Goals Application potential Flexfilm Rigid/Flex-Interconnections [Lucent] connector SMD [capicard] [Lucent] injection molded substrate Multi layer MID (with through connections) Appliction of 2D- Metallization techniques conductor path film 6

7 Basics Radiation cross linking Non Cross Linked Semi Crystalline Polymer Radiation Cross Linked Semi Crystalline Polymer Complete Melting for T > T m Rubber-elastic Behavior for T > T m soldering temperature non cross linked us cross linked non cross linked part, PA6-GF30, after lead-free soldering (T max = 255 C, 10 min) You ung s modul RT T g T m radiation cross linked part, PA6-GF30, after lead-free soldering (T max = 255 C, 10 min) 7

8 Process chain Flexfilm Criteria Adhesion of metallization Thermal expansion Thermoformability Adhesion in injection molding Solderability One of the central research targets was to find the optimal time for radiation cross linking within the process chain. 8

9 Film extrusion Film thickness PBT, film extrusion with chill-roll film thickne ess [µm] driving speed pull-off speed [m/min] High quality films with thicknesses from 200 µm to 600 µm can be extruded. 9

10 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 PBT V-PTS-Createc-B3HZC Lifocolor COLCOLOR E40/60 1 Weight-% Film extrusion Collin ESE E30M Flat film die 250 C Chill-roll 80 C Pull-off speed 1.8 m/min Film (radiation cross linkable) Thickness 300 µm Width 220 mm 10

11 Hot embossing Process windows for metallization experimental stamp layout ,5 50 peel test (according to DIN 53494) pull-off speed: 50 mm/min F copper strip Widening of specific hot embossing process window can be reached with radiation cross linking due to enhanced thermo-mechanical h resistance. Peel resistances up to 2.5 N/mm may be detected which are mainly influenced by embossing stamp temperature as key process factor. roll ( 5 mm) 30 mm test length polymer film 11

12 Radiation Cross Linking Influence on Mechanical Film Properties Specimen Type 5A Testing climate temperature 23 C, 50 % rel. humidity Test velocity 15 mm/min Tensile Test (according to DIN ISO 527) 12

13 Metallization and Structuring Radiation cross linkable PBT-films can be metallized with strip lines costeffectively by hot embossing, fulfilling the demands of high adhesive force at the same time. Hot embossing onto thermoplastic film substrates Film (radiation cross linkable) Thickness 300 µm Width 220 mm Film (circuit) 18 µm Copper + BlackOxide + Surface finishing (Tin) Hot embossing Press system (Blue Tiger Systems) Embossing temperature 183 C Embossing pressure 33 N/mm² Embossing time 0,5 sec Radiation cross linking Electron energy 5 MeV Dose 5 x 33kGy 13

14 Thermoforming Thermoformability of metallization Thermoforming mold geometry linear draw ratio R l angle α i metallization 18 µm Cu + BlackOxide elongation increase PBT, 600 µm, 5 x 33 kgy painted, without metallization T U = 230 C α i : 56.44, R l = 1.20 PBT, 600 µm, 5 x 33 kgy painted, with metallization T U = 230 C α i : 56.44, R l = 1.20 Elongation at break is ca. 2.5 % at 200 CC 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

15 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. Thermoforming of metallized film substrates Film (circuit) 18 µm Copper + BlackOxide + Surface finish (Tin) Dose 5 x 33kGy Thermoforming Berg Mini M3 Temperature of semi-finished part 240 C Mold temperature 40 CC Vacuum Thermoformed insert Various deformation degrees Steepest edge 45,6 15

16 Injection molding Film adhesion Film material PBT V-PTS-Createc B3HZC Injection molding resin PBT V-PTS-Createc B3HZC Injection molding geometry 16

17 Injection molding Injection molding - mold Multiple cartridge mold to adjust backmolding geometry to test quality of 1Adh 1. Adhesion bt between film and resin and 2. Soldering resistance 17

18 Injection molding Injection molding film + structure Thermoformed insert Different draw ratios Steepest edge 45.6 Injection molding Ferromatik Millacron 110t Melt temperature 295 C Mold temperature 80 C Injection molded multi-component part Injection molded, thermoformed, cross linked film 18

19 SMD assembly Solderability 19

20 Outlook Flexfilm Further possibilities for development steps: Combined use of copper-clad films and subtractive structuring processes Two-sided metallization with through connection Thermoforming of entire flexible printed circuits Realization of Rigid/Flex interconnections 20

21 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 ti is feasible. By hot embossing copper films onto the polymer substrate good adhesion can be 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. 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. 21

22 Acknowledgment Our special thanks go to: Bayerisches Staatsministerium für Wirtschaft, Infrastruktur, Verkehr und Technologie for founding this work within the research project NW 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 Beta Gamma Service, Saal a.d. Donau, Germany, for the electron beam irradiation of polymer films 22