cu 2 o deposition process. 2 rhodia kermel summary concept presentation technical requirements...

Cu2O deposition Process

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Summary

• Concept presentation

• Technical requirements

• Process description

• Advantages

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This new technology relies on the existence of cuprous oxide (Cu2O) in the substrate, which allows the metallization of the surface.

The particles of Cu2O are distributed in the resin which constitutes the substrate to be metallized at the rate of 2,5 to 10 % in volume.

Its transformation into pure metal, Cu°, only operates at the surface and in the micro-holes, when exposed to the contact of a specific chemical reducing agent, a borohydride, following the global reaction :

This reduction converts a discrete distribution of Cu2O particles into a continuous metallic copper layer which can be reinforced by both electroless and electrolytic processes up to the required thickness.

Plating process : Concept presentation

4 Cu2O + BH4- 8 Cu° + B(OH)3 + OH -

K+ BH4-

Cu2O particle

Resin

Cu metal layer

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Products and operation for the process application :

Cu2O particles : pulverulent powder, can be refined, dispersed within the polymeric matrix, cheap and usual product, several suppliers.

Chemical treatment before the reduction to remove the superficial layer of the matrix : to achieve high level of peel strength (see photo 1 next page), to metallize simultaneously holes and surfaces (see photo 2 next page).

Reducing agent : mainly potassium or sodium borohydride usual (several suppliers) and low cost (much cheaper than palladium), easy to handle (not hazardous, in an aqueous form), easy to use : at first sight, borohydride solution can be substituted to palladium batch in the

standard process line.

Optimization to fit the wanted requirement: concentration, size and dispersion of Cu2O particles, chemical treatment before reducing, reduction’s parameters.

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Photo 1 : Interface between the substrate and the copper obtained after a chemical treatment

Photo 2 : Very good peel strength continuity for the metal layer in surface

and holes thanks to reduced Cu2O particles

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PCB prototype that has been obtained through the Cu2O Plating Process Size of the conductor line : 10 µm.


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The Cu2O plating process is protected by 6 patents covering both laser and photovia drilling

Internal patent number International patent number Abstract

R 3043

14.12.81

France, USA, OEB (DE, BE, GB, IT, NL, SE, IR), Japan. Organic substrate metallization process using small filler particles of dispersed non conductive oxide

R 3175

15.04.83

France, USA, OEB (DE, AT, BE, SP, FR, IR, IT, LU, NL, GB, SE, CH), Canada, Korea, Japan, Taiwan, Israel, South Africa, Australia.

Metallization process of thermostable films by reducing copper oxide with borohydride followed by electrolytical deposition


R 3176

15.04.83

OEB (DE, AT, BE, SP, FR, IR, IT, LU, NL, GB, SE, CH)

Canada, USA, Korea, Japan, Taiwan

Israel, South Africa, Australia.

Electrically insulated polymeric film metallization by reducing metal oxide particles with borohydride followed by electrolytical deposition

R 3193

27.05.83

France, USA, OEB (DE, AT, BE, FR, GB, IT, LU, NL, SE, CH), Spain, Canada, Taiwan, Korea, Japan.

Possibility of using both isotropic metallizable polymeric substrates with low CTE and resin including metal oxide particles

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The Cu2O plating process has been developed in the eighties by Rhône Poulenc and suspended for strategic reasons in the nineties.


Internal patent number International patent number Abstract

R 000 99

27.07.2000

French patent deposit before international extension Compatibility of laser drilling with metallization process using reduced copper oxide with borohydride followed by electrolytical deposition

R 00181

29. 12. 2000

French patent deposit before international extension Compatibility of photovia drilling with metallization process using reduced copper oxide with borohydride followed by electrolytical deposition

2001

Patents in progress

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• Advantages

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Three requirements have been tested so far highlighting the potential of the Cu2O metallization process.

Plating process : Technical requirements

Laser drilling possibility

Peel strength potentially exceeding market

requirements

Dielectric constant features fitting market requirements

Technical compatibility

1

23

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Cu2O particles do not hinder the laser drilling quality.

Non optimized laser drilling tests for Epoxy + Cu2O

Source: Delta Electronic services

Cu2O weight concentration: 60 %in volume: 10 %


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Dielectric properties are slightly modified by the Cu2O particles and even improved in certain cases

Note: (1) In weight percentage

Properties

Superficial resistivity (/ )

Volume resistivity (/cm)

Dielectric constant Dk (1 MHz)

Dissipation factor Df (1 MHz)

3.1013

5.1014

4,9

0,019

Epoxy

3,6.1013

3,8.1015

4,8

0,018

Cu2O 22% (1)

Measures on ~ 1,6mm laminates


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When initial chemical surface treatments are done, peel strength potentially exceed market expectations.

Treatment types

Treatment 1:• Permanganate or bichromate chemical treatment.• At the end of the treatment, necessity to eliminate chromium

or manganese oxides thanks to hydroxylamine chlorohydrate or sulphate.

Treatment 2:• Alkaline chemical treatment in hydroalcoolic environment.• Potash: 350g; methanol/ethanol/water: 400cm3/50cm3/10cm3

• Temperature: 80°C.

Peel strength fluctuating according to parameters (epoxy type, particle size and dispersion(3) , physicals conditions,…).

Surface peel strength(1) for Cu2O + epoxykg/cm

Notes: (1) Tests realized ten years ago(2) 1,4 kg/cm = 8 lb/inch(3) Concentration between 10% to 50% in weight percentage

Sources: Kermel, Rhône Poulenc

0,4

0,6

0,8

1,0

1,2

1,4

1,6

1,8

2,0

2,2

2,4

2,6

2,8

Treatment1

Treatment2

Norm(2)


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With regard to peel strength, Cu2O plating process offers several potential advantages

Kermel's plating process using Cu2O particles

reduced with borohydride

Potential advantages

Very good peel strength continuity in surface and holes thanks to Cu (reduced Cu2O)

Increased peel strength compared to standard epoxy thanks to Cu2O particles anchored

inside the resin

Peel strength level modularity through control of concentration and dispersion of Cu2O

particles

Recycling possibility in case of non satisfactory level of metallization


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• Advantages

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Plating process : Description

At first sight, in the SBU layer production process, minor changes should occur in

major PCB makers production lines to implement the Cu2O metallization concept.

Changes occur principally in 2 steps :

- drilling when compared to RCC (see step 4 of the process chart),

- electroless plating with a substitution of the palladium by the borohydride

reduction bath (see step 5).

With the Cu2O metallization concept, the number of the process steps is :

- 25% less than RCC technology,

- the same than liquid technology.

SBU layer simplified production steps with CO2 laser drilling and with different

elaborated materials is presented in the 4 next slides.

Rhodia Kermel 17Note: (1) Process with window creation


• Stoving• Stacking• Pressing, heating• Disassembling/cleaning

• Coating• Drying/heating

• Coating• Drying/heating

Copper clad

Cu2Oparticles

• Half etching• Rinsing

Core preparation

Build-up deposition (coating/lamination)

Surface treatment

• Stoving• Stacking• Pressing, heating• Disassembling/cleaning

Copper line

Dielectric

Upper core layer

RCC(1) Epoxy/polyimide + Cu2O Liquid resinProduction steps

Dry filmSolids Liquids

• Micro-etching• Rinsing• Black oxydation

• Surface treatment• Rinsing



SBU layer simplified production steps with CO2 laser drilling and with different elaborated materials

Rhodia Kermel 18Note: (1) Process with window creation


• Etching• Rinsing• Photoresist stripping• Copper oxydation• Rinsing

Drilling

• Surface preparation• Photoresist deposit• Insulation • Development• Rinsing

Photoresist"window"

• CO2 drilling• Etch back• Rinsing



"Laser" resin


"Laser" resin




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Note: (1) Process with window creation

Switch the palladium deposit bath by a borohydride reduction bath

• Degreasing• Rinsing• Pre-catalysis• Catalysis• Activation


• Thin chemical copper deposit • Rinsing

• Fastened thick chemical copper deposit

• Rinsing


Electroless plating

Image transfer

Chemicalplating

Palladium

Photoresist





Photoresist



• Surface reduction with potassium borohydride

• Rinsing

Copper

• Fastened thick chemical copper deposit

• Rinsing

Epoxy/polyimide + Cu2O

• Surface reduction with potassium borohydride

• Rinsing

Copper


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Note: (1) Process with window creation


• Etching• Rinsing

• Differential etching• Rinsing



Electrolytical plating

Etching

• Copper deposit• Rinsing• Photoresist stripping• Rinsing

• Copper deposit• Rinsing• Photoresist stripping• Rinsing



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• Advantages

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Plating process : Advantages

This new plating process is :Easy to implement

- Process gets simultaneously plated holes and surfaces.- Products are usually cost competitive and easy to handle (Cu2O and borohydride).- Number of process steps reduced.- Compatibility with liquid/film technologies.

Reliable- Due to the high level of peel strength achieved.- Peel strength of plated copper increased in surface and in micro-via holes.

Technologically advanced- Reliable access to additive/semi additive processes.- Reliable access to fine line.- The presence of Cu2O particles, compatible with the dielectric and CTE requirements, enhance the thermal transfer of dielectric matrix.

Economic- Reliability and more specifically of plated micro-holes.- Saving of labor because of less steps and operations.- Saving of investment because minimum changes in production lines for PCB makers.

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As a conclusion, the Cu2O Plating Process is easy to implement, technologically advanced, and above all, reliable and economic.

In that way, our innovative plating technology : • comes up to current specifications and even exceeds the market

expectations,• answer potentially to the evolution in specifications,• is adaptable to most industrial processes.

For more information, please contact :

V. LORENTZMarketing Department

Tel : + 33 (0)3 89 20 47 44Fax : + 33 (0)3 89 20 47 38

www.kermel.com

Plating process : Conclusion

cu 2 o deposition process. 2 rhodia kermel summary concept presentation technical requirements...

Documents

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