MID Manufacturing: Advances in Metallization Plating Technologies Leading to Improved Yields 9 th International Congress Molded Interconnect Devices MID 2010 September 30, 2010 Richard C. Retallick Senior R&D Manager, Central Research rretallick@macdermid.com
Molded Interconnect Device Molded Interconnect Device (MID) A 3 dimensional structure used predominately as antennas for mobile communications Selective Plating The MID consists of plateable and nonplateable areas which predominately fall into 4 types 2
Molded Interconnect Device Main categories of selectively plated MIDs in production Double-shot no palladium (DSNP) Double-shot with palladium (DSP) Laser Direct Structuring (LDS) DSNP DSP LDS 2-shot mold 2-shot mold 1-shot mold Cr Etch Cr Etch Laser Structure Palladium catalyst Electroless Copper Electroless Copper Reducer Final Finish Final Finish Electroless Copper Final Finish 3
Manufactured MIDs Double shot no Palladium (DSNP) A 2-shot injection mold process A plateable polymer is molded d in the first shot and is then selectively l overmolded with a second non-plateable material, leaving some areas of the first material exposed. An etching step is used to roughen the plateable polymer A palladium catalyst solution is required to activate the plateable polymer to allow copper plating. Double shot Palladium (DSP) Same as above BUT palladium is impregnated into the plateable polymer. Therefore no additional activation process is required. An etching step is used to expose the palladium in the plateable polymer so that those areas can be plated with copper. Both DSNP and DSP manufacturing processes are used primarily for mass production of a single MID design. 4
Manufactured MIDs Laser Direct Structuring (LDS) A patented process developed, marketed and sold by LPKF A plastic doped d with catalyst t is molded d to form the MID Common plastic is PC/ABS (polycarbonate/acrylonitrile butadiene styrene) Many other plastic choices based on environmental factors Common dopant is a mixed metal oxide typically containing copper A laser is used to form the pattern or structure on a plateable plastic The laser ablates the plastic and exposes and reduces a catalytically active metal nuclei, typically copper. The laser also micro roughens the plastic to provide adhesion. Eliminate need for chrome etch Used for mass production of MIDs Ideally suited for rapid design changes Catalytic Ink An emerging technology for MID manufacturing Ink is applied selectively to base plastic using ink jet technologies 5
MID Process Sequence Mold Activate Copper Plate Final Finish 6
MID Copper Metallization Full Build Electroless Copper Process Two bath system = Strike Bath + Build bath One bath system Deposits copper onto the catalyzed substrate typically a minimum thickness of 12 μm is required Antenna requirement Total plating time is ± 5 hours The reaction mechanism is expressed as Cr, Cu, Pd [Cu] 2+ +4OH - + 2HCHO Cu o + 2HCOO - +2HO+H 2 + H 2 7
MID Copper Metallization Development and formulation of the strike and build electroless copper baths is critical There are a number of commercially available electroless copper bath being used for MID production Enhancements to these baths are necessary to avoid yield loss due to skip plating, extraneous plating, and bath instability 8
POP and Electronics Plating Expertise Decorative and Functional Plating on Plastics Electroless Copper for Electronics 9 A combined expertise in POP and electronics plating applications were crucial in the development and optimization of MID plating processes.
MID Plating Challenges Skip plating Bath Instability / Tank Plateout Extraneous plating 10
MID Copper Metallization Strike bath Optimized to prevent skip plating Provide uniform copper coverage High deposition rate required using reaction drivers, NaOH and formaldehyde Proprietary additives focus deposition reaction to catalytically active sites on substrate Build bath Optimized to prevent extraneous plating Proprietary additives used to control rate and focus deposition on strike copper A controlled deposition rate produces a high quality copper deposit 11
Plating of Laser Structured Materials Laser structured test vehicle (4x4 cm) with multiple lasering conditions single piece enables process optimization Different materials sets employed with this technology (PC, PCABS, Polyamide, LCP, etc.) Plating performance achieved by optimizing chemistry and matching to material choice and lasering parameters. Laser structured vehicle, shown at left, used for process optimization. 12
Electroless Copper Main Reaction drivers NaOH, HCHO, & heat Increases copper deposition rate Controlled and replenished through direct analysis in micro ons/30m 3 2.5 2 1.5 1 0.5 0 0 3 6 9 12 [NaOH] g/l 13
Reaction stabilizers Proprietary chemical additives, & air Electroless Copper 3.5 3 Decreases copper 2.5 deposition rate 2 Controlled by direct analysis and maintenance 15 1.5 additions 1 in micro ons/30m 0.5 0 0 2 4 6 8 10 12 [stabilzer] ml/l 14
Side reactions Electroless Copper Cannizzaro The non-productive reaction and consumption of NaOH with HCHO to sodium formate and methanol 2 HCHO + NaOH HCOONa + CH 3 OH By-product build-up Measured by increase in specific gravity Caused by reaction products from copper deposition reaction and Cannizzaro reaction. CuCl 2 + 4NaOH + 2HCHO Cr, Cu, Pd Cu o + 2HCOONa + 2NaCl + 2H 2 O + H 2 Leads to bath instability & tank plate-out 15
Electroless Copper Electroless Copper Effects of main analyzable components Copper Low copper concentration will sacrifice initiation especially on LDS substrates High concentration can lead to bath instability due to insufficient chelator ratio OH In Strike bath - Low concentration will cause poor initiation coverage particularly on LDS substrates In Build bath Low concentration will slow down plating rate effecting output (productivity) High concentration may lead to over activity, high deposition rates and bath instability 16
Electroless Copper Effects of main analyzable components HCHO (formaldehyde) Electroless Copper Low concentration will degrade coverage High concentration may lead to bath instability and increase non-productive side reactions Temperature Primary contributor to deposition rate LDS» Strike bath must be run at higher end of operating range to initiate plating DSNP and DSP» Strike bath should be run at lower end of operating range to prevent bath instability due to Pd from substrate 17
Electroless Copper Effects of Proprietary additives Bath stabilizer Electroless Copper Helps control deposition rate and prevent formation and accumulation of insoluble Cu +1 salts Controls deposition rate and bath stability Periodic replenishment or maintenance adds are based on site-specific operation (bath loading and production volume) Reaction site enhancers Focuses the deposition reaction to the catalytically active sites on the substrate 18
Consistent Process Control Process Control - Plating Rate 90 80 Cu Micro inches - 30 Minutes 70 60 50 40 30 20 10 copper plating rate analyzed by standardized rate panel method each operating shift assures bath life and high plating yields Strike Build 0 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 Operating Shifts 19
Assuring High Yields A combination of the best chemistry and adherence to best practice process control assures high production rates, low costs, and the highest yields. This includes the use of simple, effective chemistry controllers. 20
Assuring High Yields Reserve Formaldehyde Replinishment B Replenishment C Replenishment Heater Back Air Agitation control Valve Solution Sparger Pump Air Agitation Control Valve A Replenishment Filter Bag Front To Copper Trap Solution Height Control Proper equipment selection and engineering also strongly influences plating productivity and yields. Suppliers must work with fabricators to assure that plating tanks are designed and operated properly 21
Successful Process Demonstration Electroless copper process enhancements are designed to deliver: High yields on laser structured, two-shot, and single shot parts from the same chemistry Stable plating chemistry with long and predictable bath life Process simplicity: Easy to use and control. Predictable plating behavior. 22
Successful Process Demonstration Demonstrated in piloting and in large scale production (China) to deliver 98%+ plating yields. Consistent plating rates and high yields obtained through simple and reliably controllable chemistry Customer training on best practice operation provided to assure ongoing success 23
Continuous Process Development Electroless Copper High speed build process Target deposition rate of 5μm/hour < 3 hours to achieve 12μm 1 bath system Eliminates need for copper strike bath Provides more process tanks for higher output Reduces number of active components Provides ease of operation and reduced inventory Alternative Surface Finishes Opportunities to optimize RF and electrical performance 24
Thank you for your attention Contributors: John Swanson Director, Final Finish and Interconnect Technologies jswanson@macdermid.com Robert Hamilton Technology Manager, MID Technologies rhamilton@macdermid.com Ying (Judy) Ding Senior Research Chemist, Central Research jding@macdermid.com 25