Molded Interconnect Device Molded Interconnect Device (MID) - PowerPoint PPT Presentation

MID Manufacturing: Advances in Metallization Plating Technologies 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) Device (MID) – A 3 dimensional structure used predominately as antennas for mobile communications • Selective Plating – The MID consists of plateable and non- plateable areas which predominately fall into 4 y 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 Palladium catalyst Electroless Copper Electroless Copper Electroless Copper Electroless Copper Reducer Final Finish Final Finish Electroless Copper Electroless Copper Final Finish 3

Manufactured MIDs • Double shot no Palladium (DSNP) – A 2-shot injection mold process – A plateable polymer is molded in the first shot and is then selectively A l t bl l i ld d i th fi t h t d i th l ti 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 g p g p p y – 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 An etching step is sed to e pose the palladi m in the plateable polymer so that those areas can be plated with copper. Both DSNP and DSP manufacturing processes are used 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” with catalyst is molded to form the MID A l ti “d d” ith t l t i ld d t f th MID • Common plastic is PC/ABS (polycarbonate/acrylonitrile butadiene styrene) • Many other plastic choices based on environmental factors y p • 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 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 p • 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 Coppe ate Final Finish 6

MID – Copper Metallization • Full Build Electroless Copper Process – Two bath system = Strike Bath + Build bath – Two bath system = Strike Bath + Build bath – One bath system • Deposits copper onto the catalyzed substrate Deposits copper onto the catalyzed substrate – typically a minimum thickness of 12 μ m is required • Antenna requirement – Total plating time is ± 5 hours • The reaction mechanism is expressed as Cr, Cu, Pd Cu o + 2HCOO - + 2H O + H Cu o + 2HCOO + 2H 2 O + H 2 [Cu] 2+ + 4OH - + 2HCHO [Cu] 2+ + 4OH + 2HCHO 7

MID – Copper Metallization • Development and formulation of the strike and build f h ik d b ild electroless copper baths is critical • There are a number of commercially available electroless copper bath being electroless copper bath being used for MID production • Enhancements to these baths are necessary to avoid yield t id i ld loss due to skip plating, extraneous plating, and bath instability 8

POP and Electronics Plating Expertise Decorative and Functional and Functional Plating on Plastics Electroless Copper for Electronics A combined expertise in POP and electronics plating applications were crucial in the development and optimization of MID plating processes. 9

MID Plating Challenges • Skip plating • Bath Instability / Tank Plateout • Extraneous plating 10

MID – Copper Metallization • Strike bath • Build bath – Optimized to prevent skip – Optimized to prevent plating plating extraneous plating extraneous plating – Provide uniform copper – Proprietary additives used to coverage control rate and focus deposition on strike copper – High deposition rate required g p q using reaction drivers, NaOH – A controlled deposition rate and formaldehyde produces a high quality copper deposit – Proprietary additives focus deposition reaction to deposition reaction to catalytically active sites on substrate 11

Plating of Laser Structured Materials • Different materials sets employed with this l d ith thi technology (PC, PCABS, Polyamide LCP etc ) Polyamide, LCP, etc.) • Plating performance achieved by optimizing achieved by optimizing chemistry and matching to material choice and lasering parameters. • Laser structured vehicle, shown at left, used for h t l ft d f process optimization. Laser structured test vehicle (4x4 cm) with multiple lasering conditions single piece enables process optimization enables process optimization 12

Electroless Copper • Main Reaction drivers 3 – NaOH HCHO & heat – NaOH, HCHO, & heat 2.5 – Increases copper deposition rate in 2 2 ons/30m – Controlled and replenished through direct 1.5 analysis analysis micro 1 0.5 0 0 3 6 9 12 [NaOH] g/L 13

Electroless Copper • Reaction stabilizers 3.5 – Proprietary chemical – Proprietary chemical 3 additives, & air – Decreases copper 2.5 in deposition rate ons/30m 2 – Controlled by direct analysis and maintenance analysis and maintenance 1.5 1 5 micro additions 1 0.5 0 0 2 4 6 8 10 12 [stabilzer] mL/L 14

Electroless Copper • Side reactions – Cannizzaro Cannizzaro • The non-productive reaction and consumption of NaOH with HCHO to sodium formate and methanol 2 HCHO + NaOH 2 HCHO N OH HCOONa + CH 3 OH HCOON CH OH • By-product build-up y p p – Measured by increase in specific gravity – Caused by reaction products from copper deposition reaction and Cannizzaro reaction and Cannizzaro reaction. Cr, Cu, Pd Cu o + 2HCOONa + 2NaCl + 2H 2 O + H 2 CuCl 2 + 4NaOH + 2HCHO – 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 p g effecting output (productivity) – High concentration may lead to over activity, high deposition rates and bath instability 16

Electroless Copper • Electroless Copper – Effects of main analyzable components • HCHO (formaldehyde) – Low concentration will degrade coverage – High concentration may lead to bath instability and increase High concentration may lead to bath instability and increase non-productive side reactions • Temperature – Primary contributor to deposition rate Primary contributor to deposition rate – LDS » Strike bath must be run at higher end of operating range to initiate plating 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 to prevent bath instability due to Pd from substrate 17

Electroless Copper • Electroless Copper – Effects of Proprietary additives p y • Bath stabilizer – Helps control deposition rate and prevent formation and accumulation of insoluble Cu +1 salts 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 Focuses the deposition reaction to the catalytically active sites on the substrate 18

Consistent Process Control Process Control - Plating Rate 90 80 s 30 Minutes 70 60 inches - 3 50 Strike Build 40 Cu Micro 30 copper plating rate analyzed by standardized rate panel 20 method each operating shift assures bath life and high plating yields 10 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 adherence to best practice” process control assures high production rates, low costs, and t l t d the highest yields. This includes the use of simple, effective chemistry controllers. 20