QFN Singulation CSR (1063258), страница 2

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Thevast majority of these attributes derivefrom the product’s functionality. Themain dicing parameters to be optimized,aside from the blade selection, whichwill be discussed later, are listed below.Mounting. For tape: tape thickness,depth (relevant for both tape andnormally the shorter cut length is to bediced first; alignment, kerf check, andkerf position correction.Blade OptimizationBesides the dicing equipment, theblade is probably the most importantpart involved in the singulationprocess. The QFN materials compositerequirements challenge the blade toimpossible to blend in a single bladesuitable for very ductile materialsand very brittle materials at the sametime.

This contradiction can only beaddressed by a trade-off analysis thatweighs various requirements such as,quality, blade longevity, and cost.When QFN/MLP was introduced intothe industry, the initial feed rate was~5mm/sec. Today, the majority of theusers are even running at 100mm/sec.This high feed rate has become possiblepartially as a result of improved QFN/MLP substrate geometry (using halfThe most common blade used todayfor QFN singulation is a phenolic resincontinue to demand faster feed rates,longer blade life, and cut quality, whilemaintaining feed rate and blade life.Along with these considerations, usersalso strive for low cost.The main goal of any blade used forsingulating QFN substrates is the abilityto maintain a long blade life whilemaintaining its kerf size.

This attributeis essential for the tight tolerance towhich the final device/package sizeis subjected. Any side wear on theblade will eventually affect the deviceat compromising on feed rate and/orquality to achieve the blade life. Resintype blades do have a higher radialwear, which helps maintain a goodkerf profile, and at the same time, theright device size.

Metal sintered bladesdo have less radial wear, but they areprone to side wear over time. Suchwear would eventually be reflected inthe device size as shown in Figure 7.Metal sintered blades are harder andtend to result in larger burrs.quality or throughput would require aof the dicing process as maintainedmanufacturing techniques.Most blade parameters do changefrom user to user depending on thesubstrate geometry structure and thequality requirements. Tables 1 and 2list a few general blade parameters usedin the QFN market.Increasing UPH While MaintainingCut QualityThe QFN application has been in themarket for about a decade and a halfwith a continuous demand to improveInitial production feed rate was ~5mm/sadhesion force, adhesion relief, anddevice size, proper vacuum condition tohandle the device.Cooling.

Type (regular water, D.I.,Blade dressing and override.Spindle RPM and feed rate. Cut32Chip Scale Review Sept/Oct 2012 [ChipScaleReview.com]Figure 7: Effect of too much side wearSubstratethickness (mm)Devicesize (mm)MountingBladeMatrixBladethicknessDiamondgrit size (µm)0.8 – 1.21 x 1 up to 12x12TapeResin.008"-.020"0.200-0.508mm45 - 880.8 – 1.23 x 3 up to 12x12Tape-less45 – 88 - ResinResin &.008"-.020"Sintered 0.200-0.508mm 40 – 53 -SinteredTable 1: General blade parameters for standard QFN packagesSubstratethickness (mm)Devicesize (mm)MountingBladeMatrixBladethicknessDiamondgrit size (µm)0.4 – 0.61x0.6, 1x1 up to 4x4TapeResin.008" - .012"45 - 530.4 – 0.61x0.6, 1x1 up to 4x4TapeMetalSintered.008" - .012"35 - 45Table 2: General blade parameters for thin QFN packageswith a life span of about 200-300m.Today, end users are dicing standardQFN production at up to 100mm/swith a life span of about 2,000m.There is unrelenting pressure from thecompetitiveness, blade manufacturerscontinually invest in R&D programsaimed at developing new bladematrices, i.e., new resin formulations,Figure 8: Wear comparisondiamond types and fillers, in order tomeet demanding requirements.Recently, we developed new resinperformance than currently available.Figure 8blade wear to previous matrices andhas been shown to comply with thequality requirements while maintaininga longer life.BiographyGideon Levinson is a practicalmechanical engineer and graphicdesigner who studied at theTechnion – the Israeli Institute ofPhiladelphia.

He is a senior R&Dspecialist, dicing consumables, at ADT- Advanced Dicing Technologies; emailglevinson@adt-co.comChip Scale Review Sept/Oct 2012 [ChipScaleReview.com]33.

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