bd technology

EACH SUCCESSIVE GENERATION OFOPTICAL DISC – CD, DVD, Blu-ray Disc – hasraised the bar in terms of production

processes and tolerances. This is no surprise,because each new format has packed more dataonto a 12cm disc, dramatically reducing discspecifications and demanding even higher levels ofaccuracy. The galvanics and stamper preparationprocesses of optical disc manufacture basicallyconsist of taking a glass master and using anelectroforming process to produce a family ofstampers. Stamper preparation includes checking,polishing and punching.

“In electroforming, the big challenges are togrow a hard and flat stamper in the shortesttime possible. There is nothing new here. This isthe challenge in DVD and it is the samechallenge in BD stamper making,” notes DanHemperly, technical sales manager of RecordProducts of America.

Although the basic processes are the same, thetolerances demanded are quite different. Datacompiled by Sibert, for example (see side panel onpage 22), shows that the stamper thicknessspecifications for first-generation CD were 280-300microns, compared with 290-300 microns for DVD.For Blu-ray Disc, it is exactly 297 microns. Theacceptable thickness deviation for Blu-ray Disc is+/-3 microns, half that for CD and one micronfewer than for DVD.

Other specifications, such as eccentricity, ID hole size, punched ID radius and acceptable levelsof stress deformation, are also much tighter forBlu-ray Disc.

This raises the issue of whether these tightertolerances have changed the disc manufacturingprocess for Blu-ray Disc. Alex Greenspan, presidentof Digital Matrix Corporation, says: “From agalvanics point of view, the basics of Blu-ray andDVD are the same – you start off with a master.The Sony PTM system for BD mastering, however,employs a different technology mastering systemwhich uses a silicon wafer instead of glass.”

Greenspan adds that other systems (such asODC Nimbus’s) use glass as the master substrate.“For the silicon wafer, we have made some fairlyimportant modifications to the workholder,” notesGreenspan. “With Blu-ray you have to use a specialworkholder, because you’re using a silicon wafer,which is more delicate than glass.

“The interesting thing about the silicon wafermaster derived from the Sony PTM mastering isthat the wafer can be used multiple times togenerate fathers – up to 10 fathers. With a

photoresist master, it’s a one-shot system. Eitherway, the main difference between DVD and Blu-rayis that the specifications are tighter all the waydown the line for Blu-ray.”

Stefan Knipper, product manager,microtechnologies, technotrans, agrees: “Actually,the plating process is very similar, and mostcustomers use identical parameters, apart from thefinal current. This is higher than for DVD becauseof the larger surface area (the diameter of a DVDmaster is usually around 160mm, 170mm or180mm, while for BD it is either 180mm or200mm). This means the process times are alsosimilar, if not identical.”

Greenspan notes: “There are only a few changesin the plating process from DVD to whenupgrading to Blu-ray. The primary change is in themastering process need for better workholderdesigns to accommodate the various BDmastering substrates.”

TECHNOTRANS MARKETS THE LATEST version of themodec.line. This consists of the three-cell platingunit modec.eps, and the modec.ts for the surfacetreatment. “Both systems are proven workhorses,with unique stability regarding processrepeatability,” says Knipper. “They allow thecustomer to optimise every process step individually,until it reaches the quality that is demanded. Thanksto the simple maintenance of the system, and thelong-lasting consumable parts, this quality can bemaintained forever, with only a very smallreadjustment required.”

When it comes to comparing DVD and Blu-ray Disc production processes, Knipper saysthe major differences are related to the farhigher sensitivity of the BD product. “It requiresmore care regarding the handling and storage of

the substrates; more cleaning and cleanliness,and a higher repeatability of each individualprocess step.”

Another difference is that the family process ismore critical than with DVD. This is because of thesmaller structure size – too strong a passivationprocess can damage the geometry of the pit. As aresult, the process window for each productionstep is tighter.

Knipper adds: “The ability to compensate for astamper quality issue elsewhere in the replicationline (for example, with tighter mouldingparameters), is no longer possible. The entireprocess, from mastering to stamper production,

20 | one to one | July/August 2009 www.oto-online.com

Disc technology has advanced significantly in recent years, but have production techniquesmoved at the same pace to ensure the right quality of discs? George Cole finds out

Post-mastering: galvanicsand stamper preparation

technotrans’s modec.line – a ‘proven workhorse’

Sibert SPS can finish and process up to 12 stampers

“WE WERE READY FORTHIRD-GENERATION[OPTICAL DISC] FOURYEARS AGO”JAMES GRAY, SIBERT

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moulding to replication, must be optimised foreach other. This leads to the situation in which nosingle step can be out of spec.”

As a result, the challenge is to keep eachindividual step 100 percent repeatable, and to keepthe conditions and parameters of each step stable,so that even a mishandling by an operator doesn’tcause any variation in the quality of the stamper. “Ifyou look at the pure specification of a BD stampercompared with a DVD stamper, you hardly see a bigdifference,” says Knipper.

“The problem is that you have to fulfil this specwith every part every time – independent of theoperator. As stamper production is traditionally amanual process, each process step must be so clearand stable, that the operator has no influence overit.” The key to success is consistency at all timesand that is a tall order.

TIGHTER CONTROLS ON BATH CHEMISTRY ARE ALSOBEING IMPLEMENTED in order to ensure a successfultransition to Blu-ray Disc. This means performingtitration tests at more frequent intervals to ensurethat bath concentrations are stable, resulting in ahigher yield. “Training and re-training are alsocritical,” says Greenspan. “The Blu-ray Disc galvanicprocess works best if the technicians follow thegiven protocol and are consistent with maintainingthe parameters provided – in other words,double-check the check list.”

Greenspan adds that many factors affect thesuccessful production of BD stampers:“Passivation times, current and solutiontemperature are all critical to successful familyseries. High temperatures are often the cause of afailed BD stamper. Extensive and pure deionised

water rinsing is also vital to a flawless stamper.” Aforced jet rinse and two-sided, spin-dry assuresthe removal of any leftover impurities. Otherprocess parameters such as current ramp,solution temperature, pH and Ni concentration allneed to be monitored and maintained within atighter window.

Hemperly notes: “The electroforming processis customised by each of our customers and isquite different from one site to another. Some ofthe technotrans plating tank users are using 40-year-old technology with S-nickel, and theyare making very nice flat stampers. Other sitesare doing the same barite electroforming processwith S-nickel and Digital Matrix and Alphaplating systems. These systems use a contactring to grow the stamper.

“RPA manufactures workholders and contactrings for these kinds of systems. We also makeworkholders that eliminate the need for usingcontact rings. We have one client who uses R-nickel and does not require any contact ring,and they grow remarkably fast, hard, and flatstampers for CD, DVD and now they are beginningBD stamper making.”

The passivation process also needs to bereviewed, optimised and maintained, addsGreenspan: “You have to take extra care whenseparating the mother from the father, so there’sbeen a tightening of the parameters and there’sless tolerance. As a result, the time taken for theentire process has been extended by as much as 50percent, though it varies from one facility toanother. Eventually, the process will become morecomfortable and it will become close to where weare with DVD manufacturing. The same thinghappened when DVD first hit.”

BECAUSE OF THE SMALLER DIMENSIONS USED byBlu-ray Disc, small micron-sized or even large nano-sized contaminates can ruin a stamper andthus have a bigger impact on yields. That is why itis more critical than ever to keep the bath filteredand to ensure that the surrounding area is as freeof dust particles and other airborne contaminantsas possible.

“Another difference is that faults and defects youdidn’t see before or were tolerated before – such asdimples and creases – are not well tolerated withBlu-ray,” adds Greenspan. “We use a shadow-castingsystem, which reflects light off the surface, and we examine the shadows. Shadow casting is now a routine part of the process for customers using Blu-ray.”

Another challenge in stamper preparation is therequirement to sand the backside while preservingsome very important properties of the stampers,notes Hemperly: “For example, the total thicknessvariation is controlled not only by the

electroforming process, but also by thebacksanding process.”

What is also clear is that different companieshave developed different solutions and processesfor the galvanic and stamper preparation processes.Hemperly notes that three or four Blu-ray Discstamper companies using RPA punching and sanderequipment are all using custom processes to maketheir stampers. Cinram’s plant in Pennsylvania(which is using RPA’s P-114T Punch and P-141Backsander), for example, is using blue tape toprotect the stampers and a precision deburringprocess on the stamper before sending it toreplication. The backsanding operation is wet andthe deburring operation is dry. Another plant, L&MWest Optical Disc in LA, is using RPA’s P-114T Punchand P-105 Backsander to make BD stampers. “Theyare, in essence, using the same stamper-finishingprocess for BD as used for DVD,” notes Hemperly.

Sony plants are using RPA’s P-117 Tape ApplyMachine to tape the BD stampers prior tobacksanding. “They then remove the tape and

bd technology

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Synchronicity’s Tom Whitworth holding the first stamperpunched with the new P-145 NanoPunch from RPA

“THE MAIN DIFFERENCEBETWEEN DVD ANDBLU-RAY IS THAT THESPECIFICATIONS ARETIGHTER ALL THE WAYDOWN THE LINE FORBLU-RAY”ALEX GREENSPAN,DIGITAL MATRIX CORPORATION

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replace it with RPA’s R1000A tape, including a holewhere the ID will be punched. Punching the baremetal without punching through the protectivetape provides the best quality hole with minimumbend at the resulting ID hole. The same BDstamper process is being performed at Technicolorusing the RPA taping equipment and RPA tape,”says Hemperly. Synchronicity Mastering in Salt LakeCity will soon be making recordable BD stampersusing RPA’s P-145 NanoPunch, which automaticallypositions and punches the stamper with aneccentricity below 2 microns.

Sibert Instrument’s Stamper PreparationSystem (SPS) includes the SPS Finishing machineand SPS Punch machine. Sibert uses a wetfinishing system and other features include aprogrammable X-Y Finishing Head for creatingdifferent surface finish patterns. A unique featureis the ability to stack stampers, and finish andprocess up to 12 stampers. SPS has been designedto be very flexible – it’s a modular system andvarious upgrade options are available.

“They can be bolted together, so the finisher canwork with the punching machine, and you don’thave to change machines,” says James Gray, Sibert’smanaging director. The punching machine alsooffers standard and reverse punching, so users onlyrequire the one machine.

“Sony chose our equipment,” adds Gray, “that’swhy our equipment stands out. It’s because it’sbeen developed with third generation in mind but itcan also cope with CD and DVD.” Gray adds thatSibert had long planned for a format like Blu-ray:“We were ready for third-generation [optical disc]four years ago. We were approached by Philips sixyears ago in China and they said they were talkingabout the next-generation disc.” Gray says thatSibert invests heavily in research and development,and as a result, was well placed for the launch ofthe next-generation HD formats.

Hemperly says that a lot of what has been learnedabout punching and polishing DVD and recordablestampers has been used in the development of RPA’sBD punching and polishing equipment, such as the

ability for punch machines to punch in the upwardsdirection. This means that the male punch enters thestamper from the backside and upwards through thedata side. From this, RPA developed methods forprotecting the stamper, with tape leaving the centrehole area unprotected, so that it’s possible to punchthe naked metal. “This technique provides the bestpossible quality hole and it has become the standardfor the BD stamper making process,” says Hemperly.RPA’s experience with the recordable industry alsotaught the company how to properly hold thestamper for backsanding. “Additional care isnecessary when backsanding the recordable stamperand the same is true for the BD stamper.”

For example, stress can be induced into thestamper if it is backsanded with the hole in theprotective tape. For this reason, one of RPA’s clientsapplies R1000A tape, covering the complete stamperfor backsanding, and then removing that tape andreapplying new tape containing a hole where thestamper is punched. “We really hate to see this,because it seems such a waste of tape, and our pushis always to be green,” says Hemperly. “However, it isnecessary to get the precision back-finish, with lowstress, and a perfectly punched hole in the stamper.”

Gray notes that the metal condition can affectthe punch quality of the hole: “Take a block of butterout of the fridge and you can cut it with a knife. Butraise the temperature by a fair degree and you can’tcut it. If you grow the stamper too soft or too hard,you will have punch problems.”

THE STANDARDISATION OF SPECIFICATIONS andproduction processes helps to produce consistentresults across the industry. Last year, Sony, SingulusMastering, Singulus Technologies, Sibert andtechnotrans formed a working group to define a defacto standard for Blu-ray Disc stamper properties.The group produced a 13-page document, ‘Blu-rayDisc Stamper Physical Characteristics’, which coveredvarious parameters including, hardness, thicknessvariation, flatness, diameter, burr, eccentricity,roughness and visual appearance. [see One to One,issue 219 (April 2009), page 36.]

“We were asked to join this workgroup as wehave a very close relationship with all the masteringcompanies. The main reason for forming this groupwas to set the standards required for a highlydemanding product such as BD, but also to developthe production steps required for BD stamperproduction with at least two different masteringsystems,” says Knipper.

The group exchanged all relevant informationand created smaller workgroups to solve specifictechnical problems. At the end, says Knipper, all theresults were put together and the final document,

complete with process flowchart, was prepared. “Themajor benefit of this workgroup was that each ofthe parties involved learned a lot about the specificdemands of the other parties,” he adds.

“As for Blu-ray Disc, the quality of one productionstep is very much dependent on the quality of thepreceding step, and the work group had a uniqueopportunity to listen and learn from each other. I’msure that this avoids many problems in the market ifa Blu-ray Disc production system is started. Ofcourse, some individual challenges still remain butthey are worked out by each vendor.”

Knipper admits that the workgroup was mainlytechnically driven, which might have led to a lack ofacceptance by parts of the industry. “But I don’tthink this is caused by the existence of theworkgroup; I assume it’s more because it’s difficultfor some people to accept this production process isso much more sensitive than DVD, and they have todepend so much more on the machine suppliers.They have fewer opportunities to optimise theproduction process (and the costs).”

Sibert already had a close working relationshipwith Sony, having set-up its first Blu-ray Disc systemmore than two years ago at Sony’s Terra Haute site:“It was a semi-beta site and we worked a lot withSony on finalising the processing side of ourequipment to all the relevant criteria,” says Gray.

Greenspan says that the Blu-ray stamperstandards workgroup was a surprise to DigitalMatrix. “We were not invited to be involved. We haveworked in groups in the past, even with ourcompetitors, and it’s worked out well. I think theintentions behind this group are good, but theindustry has shrunk – there are only a few masteringcompanies out there. They are competing for arelatively small market and it’s going to be moredifficult for companies to get involved withoutcommercial friction coming into play. Having saidthat, we are willing to participate in an open forum,as long as it does not become a vehicle to promoteone company over another.”

“RPA was not invited to be part of the group,”says Hemperly. “RPA has simply partnered with thecompanies that are tasked with making DVD and BD.We have been very successful supporting the guysthat are actually doing much of the work.Unfortunately for RPA, some of our best clients haveneeded to get competitive products solely on thebasis of their white papers and marketing. We didn’testablish the standards; we just make the bestequipment to meet or exceed the standards.”

bd technology

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�� www.digitalmatrix.us �� www.globalprint.com �� www.recordproducts.com �� www.sibert.co.uk �� www.synchro-mastering.com

STAMPER SPECIFICATION

Stamper Property First Generation CD Second Generation DVD Third Generation BD1) Hardness Data Face: 220HV - 270HV0.32 20HV - 270HV0.3 200HV - 220HV0.32) Hardness Rear Side: 160HV - 210HV0.3 180HV - 220HV0.3 180HV - 200HV0.33) Hardness Differential 20HV - 80HV 40HV - 70HV 30HV - 50HV

Data to Rear Face:4) Stamper Thickness: 280μm - 300μm 290μm - 300μm 97μm5) Thickness Deviation: + / - 6μm + / - 5μm + / - 3μm6) Protective Coating: < 100μm < 80μm Punch ID area clear7) Punching Arrangement: Standard Standard L0 / Standard L1 Reverse L0 / Standard L18) Punched ID radius <300μm <200μm L0 / <200μm L1 0μm L0 / <100μm L1

(data side):9) Eccentricity, ID to Data 0μm - 20μm 5μm - 10μm <5μm10) ID Hole Size / Tolerance: 25mm - 37.6mm / 10μm – 16μm 21mm - 25mm / 5μm - 10μm 22mm / 0 - 5μm 11) OD Hole Size / Tolerance: 128mm - 144mm / ± 0.5mm 128mm - 138mm / ± 0.5mm 38mm / ± 0.1mm12) ID Burr: <10μm(Rear) <10μm (Rear) L0 <10μm / L1 <10μm13) OD Burr, Rear Side: <20μm <20μm <10μm14) Rear Side Surface Finish: Ra 1.5μm - 1.0μm / Rt < 1.5μm Ra 1.0μm - Ra 0.04μm / Rt < 1.0μm Ra 0.05-0.08μm / Rt<0.6μm15) Stress / Deformation <4mm <2mm L0 <3mm / L1 <1mmInformation collected from OEM sources, subject to change. Source: Sibert Instruments

“THE ENTIRE PROCESS,FROM MASTERING TOSTAMPER PRODUCTION,MOULDING TO REPLICATION, MUST BE OPTIMISED FOREACH OTHER”STEFAN KNIPPER, TECHNOTRANS

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