FRIT FACTS

A Brief Technological Summary OfTELEVISION SOLDER GLASS

For CRT Technicians,Engineers And Managers

TECHNEGLAS Spans The Globe

Courtesy of TECHNEGLAS, INC.

Technical ProductsLevis Development Park, Bldg. #52

Perrysburg, OH 43551

Phone 419-247-7032Fax 419-247-7071

2

Frit SeminarContents

1. Composition and Properties

2. Frit Types and Specifications

3. Mixing and Dispensing

4. Drying and Dielectric Strength

5. Frit Lehr Sealing Cycle

6. Seal Geometry and Stresses

7. Thermal Rates and Differentials

8. Exhaust Cycle and Implosions

9. Salvage Process

10. High Strength TV Solder Glass

11. General Discussion

TECHNEGLAS

3

Composition And Properties

Television Solder Glass has been used to seal color CRT’s sincethe 1950’s. TV Solder Glass is commonly called “frit” in theindustry. The word “frit” refers to the ground powder form inwhich frit is produced and shipped. The average size frit particleis about 20 microns - about one third the diameter of a humanhair. The largest particles are about 150 microns (0.15mm).

Frit is designed to CRYSTALLIZE during the frit sealing cycle, sothat the bulb can withstand an exhaust cycle without undergoingparts shift or seal softening.

The frit glass contains five major ingredients, plus stains andadditives:

These three ingredients These two ingredients form aform crystals during glass which binds the crystalsfrit sealing. together in the finished seal.

TECHNEGLAS

Composition And Properties

4. Barium Oxide ~ 2%5. Silicon Dioxide ~ 2%

1. Lead Oxide ~ 75%2. Zinc Oxide ~ 12%3. Boric Oxide ~ 9%

4

A mixture of two types of crystals develops during the frit seal:

Small, slow-growing2 Lead, 1 Zinc, 1 Boron

Large, fast-growing1 Lead, 2 Zinc, 1 Boron

40microns

15microns

2 PbO-ZnO-B2O3 PbO-2ZnO-B2O3

The final crystallized Solder Glass looks like this:

BaO-SiO 2Glass

Because solder glass is a high lead material, it is considered aHAZARDOUS MATERIAL, and the primary exposure route isthrough inhalation or ingestion. Disposal should be asHAZARDOUS WASTE, EPA Waste ID Number: D008.

TECHNEGLAS

5

Typical Frit Types And SpecsThe three most widely used television frits sold by Techneglasare:

The sealing behavior and general specifications for these frits areidentical.________________________________________________

Frit Properties and General Specifications

Property Test Conditions Typical Specification

Button Flow 440�C, 60 Min. 27.4mm +/- 0.8mm

Rod Seal (Comp.) 440�C, 60 Min. 40 +/- 30 Kg./Sq.Cm.

DTA Peak Time 440�C Isothermal 22 +/- 5 Min.

DTA Completion Time 440�C Isothermal 30 +/- 6 Min.

Glassy Edge Gradient Boat 60 Min. 370�C +/- 6�C

Crystallization Edge Gradient Boat 60 Min. 420�C +/- 6�C

Sieve Analysis Percent - 37 Microns 68 +/- 5%

Dispensing Bead Width Amyl Acetate Vehicle 6.5mm +/- 1.0mm (12.5 to 1 Frit/Vehicle Ratio)

TECHNEGLAS

FRIT TESTING

CV-1608

Black Contains1% Mn203

Colorant

CV-685

Yellow DoesNOT ContainColorants

CV-1610

Gray Contains0.3% Mn203

Colorant

6

GlassFrit

0 10 20 30

Button Flow DTA Iso Time 440�C

GlassStandard 200 300 400 500

Frit

Rod Seal Gradient Boat, �CStress Mismatch

TECHNEGLAS

Manufacturing Process

7

The manufacturing process consists of six steps:

1. Batch Weighing And Mixing

2. Melting And Chip Forming

3. Ball Milling And Initial Screening

4. Blending With Additives And Pre-Test

5. Final Screening

6. Packaging

TECHNEGLAS

8

Mixing And Dispensing

To dispense Solder Glass, it must first be mixed with a two-partvehicle. One part is a solvent (Amyl Acetate or Butyl Acetate)which provides FLUIDITY to the mix. The second part is aBINDER (Nitrocellulose) which holds the frit particles on the sealedge during frit seal, until the particles melt together and flow.Usually 1 to 1.5% of the vehicle is binder. For a given vehiclesystem, the paste viscosity will increase as the nitrocellulosecontent is increased (see chart below):

Paste Viscosity as a function of % NITROCELLULOSE

0.12

0.13

0.14

0.15

0.16

0.17

0.9 1.0 1.1 1.2 1.3 1.4

Viscosity

% Nitrocellulose

NOTE: Paste viscosity is defined as the reciprocal of the beadwidth (1/mm.) as measured in millimeters using theTECHNEGLAS dispensing test.

TECHNEGLAS

9

MIXING

Mixing is best done in a closed bowl. A mixer with a stainless steel bowl andstirrer and 100-liter capacity is ideal. The ideal mixing speed depends on thetype of mixing action and the design of the mixing blade. The mostsuccessful mixers, such as Hobart or Ross mixers, incorporate a planetary ororbital mixing action that assures that there is complete homogeneity of thematerials being mixed within a few minutes. The paste viscosity decreasesas the mixing speed or the mixing time is increased (see chart). Formixers such as the Ross and Hobart, a 30-minute mix produces excellentpaste properties.

Paste Viscosity as a Function of Mixing Speed

0.160.15

0.140.13

0.12

14 17 20 23 26 29 32 35

Viscosity (1/mm.)

Paste Viscosity as a Function of Mixing Time

0.160.15

0.140.13

0.12

10 20 30 40 50

Viscosity (1/mm.)

TECHNEGLAS

10

MIXING

It is not necessary to clean bowls, mixing blades and transfervessels if they are kept closed and covered during and afteruse. This system not only saves frit, it also keeps the mixingarea clean, which reduces the exposure of lead dust to mixersand machine attendants.

The mixing, holding and dispensing areas should be at the sametemperature. Keeping these areas at the same temperature willprevent viscosity changes caused by the paste seeking a newtemperature.

Paste Viscosity As A Function Of Temperature

0.1500.145

0.1400.135

0.130

14 16 18 20 22 24 26 28 30

Viscosity (1/mm.)

After the mixing operation is completed, the paste should “rest”two hours before frit bead application to allow air bubbles in thepaste to dissipate and the viscosity of the paste to reach arelative stability (see chart next page).

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11

Paste Viscosity

As a Function of Time After Mixing

Viscosity (Reciprocal of Bead Width)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00.12

0.13

0.14

0.15

0.16

0.17Viscosity (1/mm.)

TECHNEGLAS

12

Typical Bead ShapesDispensing is best done by a robot tracking to a theoretical sealedge and a screw feeder to control the amount dispensed at eachpoint on the funnel.

Advantages & Disadvantages

Narrow

Medium

Low

+ Permits higher frit weights+ Easier tracking- Slower drying, can break off- Greater panel / funnel separation - Frit must travel farther along seal edge

+Permits adequate frit weight+ Reasonable tracking controlGood compromise on drying and green strengthPanel / funnel separation is reasonableFrit travel along seal edge is reasonable

+ Fast drying and strong+ Frit travel along seal edge is minimal+ Panel / funnel separation is minimal- Hard to achieve higher frit weights- Tends to run off seal edge

40 - 60%

60 - 80%

80 - 95%

Typical Frit Weights By Bulb Size: (Frit Weight, Wet, In Grams)

13 19 20 26 27 30 32 35

Min. 35 50 55 80 87 105 120 135

Target 40 55 60 90 95 115 130 150

Max. 45 60 65 100 110 125 145 165

TECHNEGLAS

13

Bubbles In FritNormal frit contains some bubbles from .1 or .2 mm in size, andoccasional bubbles up to .5 mm are not unusual or harmful.

Typical frit contains 2% to 7% bubbles as a fraction of viewed cross-section area.

Bubbles can be caused by:

• Space left from solvent evaporation.

• About 40% of mixed paste is vehicle. Some voids left after drying may

remain after melting.

• Bubbles introduced in mixing pot (blades, etc.).(*)

• Bubbles which do not rise - paste too thick. (*)

• Bubbles from dispense head or screw.

• These bubbles will normally appear as a row (or line) of bubbles.

• Bubbles from tearing of catenary (paste too dry).(*)

• These appear as a row or line of small bubbles in the middle of the seal.

• Oxidation of amyl acetate; C0 + C02 = H20

• Oxidation of nitrocellulose; C02 + H20.

• These are normally very small. In CV-685 they appear clean.

• Dust, dirt or fibers on frit bead.(*)

• Dirty seal edges.

• Grooving of frit bead from thin paste(*) →

(*) The usual cause of HARMFUL bubbles.

TECHNEGLAS

14

Drying

The drying of a dispensed bead is dependent on several factors:

á Time- The average bead using 1.25% nitrocellulose in amyl acetate requires 1.5

hours in ambient conditions to dry sufficiently. However, a 30-minuteoven cycle plus ambient is typical.

á Temperature- Keeping the frit bead between 50 and 75�C is a safe temperature range

for drying. If the drying profile is excessive, the nitrocellulose will begin tooxidize, or crusting of the top surface will occur.

á Type of Heating- Can be ambient air, or assisted with heating elements. Having the

funnels heated prior to fritting speeds the process.

á Placement of Heating Source- The heating source should be below the seal edge to avoid overheating,

which can cause crusting of the frit bead.

á Air Circulation- Fumes should be exhausted. Air flow should not be turbulent.

á Geometric Shape of Bead- The flatter the bead, the faster the evaporation rate due to increased

surface area and less thickness.

á Percent Nitrocellulose- The higher the nitrocellulose content, the slower the evaporation rate.

á Type of Solvent- Paste made with butyl acetate vehicle dries significantly faster.

TECHNEGLAS

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Drying

Drying Profile (Heating Vs. Ambient)Medium Profile Bead - Amyl Acetate

0 5 10 15 20 25 30 35 40 45 50 55 600

102030405060708090

100Heat 50°C Ambient

Drying Profile (Heating Vs. Ambient)Medium Profile Bead - Butyl Acetate

0 5 10 15 20 25 30 350

102030405060708090

100Heat 75°C Heat 50°C Ambient

TECHNEGLAS

Ambient ↓

↑ Heat

Ambient ↓

50°C ↓

75°C →

16

Dielectric Strength

Television Solder Glass As A Function Of Temperature

Dielectric Strength KV./mm

22 32 42 52 62 72 8212

14

16

18

20

22

24

26Pressed Powder

TECHNEGLAS

17

High Voltage BreakdownBulbs with perfectly clean seals can pass 60 to 100 KV. High Voltage breakdownis caused by contamination.

What To Look For:

á Panel Seal Edge Contamination

- Lacquer, matrix, phosphor, poor SE cleaning, conveyor marks,fingerprints.

- Manual loading of panel at the sealing lehr can contaminate the 3 and9 o’clock points.

- Improperly cleaned glass in the corners or contaminated bevels.- The corner and bevels are the most difficult area of the seal edge to

clean due to shape, surface finish irregularities, and position.

á Frit Bead Contamination

- Fibers on the dispensed bead, poor drying, oil in the paste, and“chimney” effect during frit sealing.

á Panel/Funnel Scratches

- Across the seal edge, or diagonally across in the corners.

á Funnel Contamination

- Dag or graphite or iron oxide on seal edge; poor cleaning.

- Even though the dag does not touch the seal edge, theelectrical path length through the seal is shorter, givingrise to higher current leakage.

á Induced Stresses From Banding And Evacuation (Slow Dielectric Failures)

- Mechanical stress concentrations increase chances of failure.

á Studs and Buttons (Electric Field Concentrations)

- The stud and button areas can be points of higher failures.

TECHNEGLAS

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Frit Lehr Sealing Cycle

The frit lehr cycle has a peak temperature of 446�C plus or minus 4�C. Hold timeshould be 35 to 45 minutes for sizes up to 27-inch, and 40 to 50 minutes for largersizes. The heating rate between 375 and 440�C should be 4 to 6�C per minutefor small and intermediate sizes, and 3 to 5.5�C per minute for large sizes. Thisheating rate is called the “approach” heating rate, and it affects seal thickness,bead geometry, and leading-trailing edge, “delta T”.

0 20 40 60 80 100 120 140 1600

50

100

150

200

250

300

350

400

450

Heating Approach Hold Cooling

1) Heating, usually 6 to 11�C per minute. Evaporation of remaining solvent.2) Burnout of binder, start of glass particle fusion.3) “Approach HR”. Fusion complete; wetting, flow, and fillet formation underway.4) Flow complete, wetting nearly complete. Crystal growth starts.5) Crystal growth rate maximum; crystals nearly full size.6) Crystallization completes on leading and trailing edges. 92 to 96% crystallized.7) Tube annealing.8) Cooling, slow enough not to cause breakage (2.5 to 7�C/Min.).

TECHNEGLAS

1

2

3

4 5 6 7

8

19

Events Occurring During Soak

Hold Time In Frit Seal

Fillets Formed ~ 1 Min. Wetting/Nucleation

*******

Completion

TECHNEGLAS

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Panel - FunnelSeparation

Direction of Travel

→ → → → → →

1.5 mm.

0.2 mm.

At lehr load

Start of FS "hold"

TECHNEGLAS

21

Thermal Contraction

Panel Vs. Frit

Mismatch, Kg./Sq. Cm.

0 50 100 150 200 250 300 350 400 450 500

050

100150200250300350400450500

-50-100

Frit Panel

TECHNEGLAS

22

Mismatch Vs. Holding Time

Compression in Frit at 440�C

Mismatch, Kg./Sq. Cm.

0

5

10

15

20

25

30

35

4030 45 60

30 Minutes 45 Minutes 60 Minutes

Hold Time at 440�C

TECHNEGLAS

23

Mismatch Vs. Temperature

Compression In Frit

Mismatch, Kg./Sq. Cm.

0

5

10

15

20

25

30

35

40440 445 450

440�C 445�C 450�C

Sealing Temperature

TECHNEGLAS

24

Frit Seal Thermal RatesDegrees C Per Minute

___________________________________________________________14” - 17”

Range 100-375 375-445 Hold 445 Cool RateIdeal 6-9 4.5-6.0 35 Min. < 2.5Good 9-14 6.0-7.0 30 Min. 2.5-4.5Improper > 15 > 7 < 28 Min. > 4.5

___________________________________________________________20”

Range 100-375 375-445 Hold 445 Cool RateIdeal 6-8 4.5-5.5 40 Min. < 2.5Good 8-12 5.5-6.5 35 Min. 2.5-4.0Improper > 12 > 6.5 < 32 Min. > 4.0

___________________________________________________________27”

Range 100-375 375-445 Hold 445 Cool RateIdeal 6-8 4.0-5.5 40 Min. < 2.5Good 8-11 5.5-6.5 35 Min. 2.5-3.5Improper > 11 > 6.5 < 32 Min. > 3.5

___________________________________________________________32”

Range 100-375 375-445 Hold 445 Cool RateIdeal 5-7 3 50 Min. < 2.5Good 7-10 4.5-6.0 40 Min. 2.5-3.5Improper > 10 > 6.0 < 32 Min. > 3.5

___________________________________________________________35”

Range 100-375 375-445 Hold 445 Cool RateIdeal 4.5-6.5 2.8-4.3 55 Min. < 2.5Good 6.5-9.5 4.3-5.5 40 Min. 2.5-3.3Improper > 9.5 > 5.5 < 35 Min. > 3.3

___________________________________________________________

TECHNEGLAS

25

Fillet Shape Analysis

Examination of cross-sections can be very informative. Use a glasssaw to cut at least four sections: leading edge, trailing edge, middleaxis, and a corner. These will show:

1. Parts Match

2. Fillet Shape

3. Amount of Frit

4. Seal Thickness

5. Possible Offset

6. Amount of Seal Land

7. Bevel Shape and Fill

8. Stress, if Polarimeter is Used

TECHNEGLAS

26

Fillet Shape

What to Look For:

C

C C

C

Seal thickness.2mm.

Compression near fillets

Good Seal Too muchfrit

Too much fritdispensed

inside

Thin seal

Fillet drooptemp. too high

Frit weightok

Not enoughfrit disp. ok

Not enoughfrit

TECHNEGLAS

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Fillet Shape

What to Look For:

Frit weightok

Poor trackingdisp. to outside

Panel offset to inside

D-Shapedfillet inside

frit crystalizedtoo soon

Contam. bevelor disp. too

wide

Frit weight is good

TECHNEGLAS

28

Fillet Shape

What to Look For:

Thin seal.1 mm.

Thick seal.4 mm.

Contam. lehratmosphere

Tilt

TECHNEGLAS

29

Exhaust CycleThe exhaust cycle usually has a peak temperature of 300 to 325�C. Hold time isusually brief (0 to 5 minutes). The heating rate should be kept low to avoidUPSHOCK implosions from INSIDE sources. Typical heating rates are 5 to9�C/min. for small and intermediate sizes and 3.5 to 5.5�C/min. for large sizes. Ifa major problem of “Cracked Bulbs” exists, the heating rate over the first 250�Cmust be slowed down. The COOLING RATE should be 2.5 to 4�C/min. for smalland intermediate sizes and 2 to 3�C/min. for larger sizes to avoid OUTSIDESOURCE losses.

0 20 40 60 80 100 120 140 1600

50

100

150

200

250

300

350

Heating Approach Cooling

Typical Inside Source Implosions:Studs Inside Contamination (Inside TensionOffsets Scratched Necks During Heating)Inside Frit Re-Entrants Scratched Lug Area

________________________________________Typical Outside Source Implosions:Bump Checks Frit Drips/Overlap Drips (Outside TensionFrit Seal Near Pads Button (Anode) Area During Cooling)Outside Panel Bevel Checked Pads Contamination

TECHNEGLAS

30

ExhaustWhen a new line or bulb size is started or when the speed is increased onan older exhaust line, a significant imbalance may occur in the chroniclosses between heating losses (upshock) and cooling losses (downshock).If heating losses are predominant, an effort should be made to move thepeak exhaust temperature ahead a few zones to lower the heating rate andthereby reduce upshock breakage. If cooling losses are predominant, thepeak exhaust temperature should be moved back a few zones to lower thecooling rate and thereby reduce downshock breakage.

Minimum TOTAL implosions will occur if upshock and downshocklosses are about equal.

Exhaust Curve - Heating Losses Predominant

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 300

50

100

150

200

250

300

350

Curve A - Peak Zone 9 Curve B - Peak Zone 10 Curve C - Peak Zone 11

Heating Losses - 32 Heating Losses - 16 Heating Losses - 8Cooling Losses - 4 Cooling Losses - 6 Cooling Losses - 8TOTAL Losses - 36 TOTAL Losses - 22 TOTAL Losses - 16

TECHNEGLAS

31

Exhaust Thermal Rates Degrees C Per Minute

___________________________________________________________14” - 17”

Range 100-270 270-Ex.T Hold Cool RateIdeal 5-8 4.5-6.0 5 Min. < 3Good 8-11 6.0-7.0 3.0-4.0Improper > 11 > 7 > 4.0

___________________________________________________________20”

Range 100-270 270-Ex.T Hold Cool Rate Ideal 5-8 4.5-5.5 5 Min. < 2.5Good 8-10 5.5-6.5 2.5-3.4Improper > 10.5 > 7 > 3.5

___________________________________________________________27”

Range 100-270 270-Ex.T Hold Cool RateIdeal 5-7 4.5-5.5 5 Min. < 2.5Good 7-9 5.5-6.5 2.5-3.4Improper > 9.5 > 7 > 3.5

___________________________________________________________32”

Range 100-270 270-Ex.T Hold Cool RateIdeal 5-6.5 4.5-5.5 5 Min. < 2.5Good 6.5-9 5.5-6.5 2.5-2.9Improper > 9.5 > 6.5 > 3.0

___________________________________________________________35”

Range 100-270 270-Ex.T Hold Cool RateIdeal 4.5-6 4-5 5 Min. < 2Good 6-9 5-6.5 2-2.6Improper > 9 > 6.5 > 2.7

___________________________________________________________

TECHNEGLAS

32

Salvage Process

TTTT

TT

T

T

00

00

CC

CC

CC

CC

0

0

T

T

T

TT

T

(Hot Nitric Acid)Debead, temp. 48 to 55°C

(Hot water or acid)High temp. stabilization of

bulb~55°C

Step 1 Step 2

Step 3 Step 4

(Cold Water)Cold shock forms first crack

(Tension on OUTSIDE of

(Hot Water)Hot shock finishes crack

(Tension on INSIDE of bulb)

Salvage Losses: Causes:

Gross Breaks Excessive Thermal ShockPoor Contraction Match of PartsPoor Water Distribution

Corner Breaks Poor Contraction Match of PartsPoor Water DistributionToo Much Frit Inside Corners

Corner Pulls Insufficient Cold Shock Time(Four Fracture Planes) Poor Water Distribution

Too Much Frit Inside Corners

TECHNEGLAS

33

Salvage

Debead Etch

The optimum etch in a salvage operation removes all of theexternal frit bead and up to 2 mm. of the frit between panel andfunnel. The etch can be deeper at the corners.

Etch Uniformity

The etch must be uniform in depth. “Scalloping” is a veryundesirable condition which should promptly be corrected throughnozzle design or transducer arrangement, or by an oscillatorymovement of the bulb during etch.

Uniform etch Scalloping

TECHNEGLAS

34

Salvage

Gross BreakageExcessive Thermal ShockPoor Concentration Match of PartsPoor Water Distribution

Corner BreaksPoor Contraction Match of PartsPoor Water DistributionToo Much Frit Inside Corners

Corner Pulls(Four Fracture Planes)Insufficient Cold Shock TimePoor Water DistributionToo Much Frit Inside Corners

TECHNEGLAS

35

Thermal Contraction

450 to 25�C

This is a DESIRABLE stress condition. Bulb stress worksFAVORING effective salvage. Panel contraction midwaybetween frit and funnel.

110

F

108

P

106

Frit

GOOD

This is an UNDESIRABLE stress condition. Bulb stress worksAGAINST effective salvage. Panel too high and funnel too low.

106

Frit

BAD

109

107

P F

TECHNEGLAS

36

Salvage

Stresses Developed After Frit SealBending Stress

TT

Stresses Developed in Cold ShockBending Stress & Thermal Stress

TT

TT T

T

TECHNEGLAS

37

Salvage ProcessGROSS BREAKAGE can be reduced by having a lukewarm 40�C waterflush for 1 to 2 minutes before hot 50�C acid etch. At the conclusion of hot acidetch, a 40�C intermediate cushioning flush can be used for 5 to 10 seconds priorto the 15�C cold shock. This will cushion the 35�C differential.

CORNER PULLS can be reduced by making sure that the cold shock and finalhot shock water flow patterns are uniform over the corners. It MAY bedesirable to have a deeper etch in the corners to make final separation easierduring the final hot shock. This separation occurs when the four fractureplanes meet in the corners.

Ideal Salvage Cycle

0 1 2 3 4 5 6 7 8 9 10 11 12 130

10

20

30

40

50

60

The ideal salvage equipment is an in-line or U-shaped multiple stationmachine allowing 60 sec. per station and, having 20 stations, machine timewould be 20 min. The first two or three stations involve increasingly warmwater 35 - 45�C. The next few stations stabilize the bulb at 50�C, and beginthe acid etch process. Four to fifteen etch stations are followed by a rinsestation. Then a COLD SHOCK for about thirty seconds. Then a HOT SHOCKat 45 to 55�C. This is followed by a second set of cold and hot shocks, usedonly if necessary (double shock). Equipment is stainless steel and plastic.Each water station must have its own temperature control system and flowcontrol valves. The bottom of each station is a return sink which recirculates.Provisions must be made at the acid stations to neutralize and dispose of spentacid. Immersion sinks and ultrasonics should be avoided. A combination ofFLOW and SPRAY, panel up, is ideal. However, panel down is also workablebut, in this case, water and acid must be SPRAYED just above the seal edge.

TECHNEGLAS

Hot Acid EtchWithout Ultrasonics

Cold Shock

FinalHotShock

38

High Strength FritRequirements For High Strength

Chemical Bonding

A strong chemical bond is developed when thebeginning of crystallization is DELAYEDuntil a strong chemical reaction takes placebetween the frit and the panel and funnelglasses. PREMATURE crystallizationinhibits the wetting reaction.TECHNEGLAS high strength frits have apatented nucleation method whichprovides the necessary delayedcrystallization.

Intrinsic Strength

High strength frit must be internally strong.TECHNEGLAS high strength frits gain theirstrength from having a mixture of LARGEand SMALL crystals, bonded together withan optimal glassy matrix. The two crystalsizes are developed by using patentednucleating agents.

Proper Contraction

High strength frit must have proper thermalcontraction to enable development of zones ofCOMPRESSION in the panel and funnelglasses. The compression prevents crackinitiation. TECHNEGLAS high strength fritshave optimum stress characteristics withoutuse of high levels of filler materials. Atypical maximum filler content is 1.5percent, with 1 percent being typical.

C

C

P

F

39

Bulb Pressure Test

Strength Comparison

Normal High Strength0

20

40

60

80

100Pressure test

Pressure test 68 82

TECHNEGLAS

40