PCB_MF

Properties of Copper1.Dielectric strength2.Dielectric constant3.Dissipation factor4.Surface & Volume resis5.Foil to base bond stren6.Flexural strength7.Water absorption8.Flatness9.Flame resistance & app

Clad Laminate:stancengthpearance

2.2.1ELECTRICAL PR1.Dielectric Strength:It is the ability of an insresist passage of electric It depends on•chemical composition• molecule structure• degree of moisture• voltage applied•thickness of material•ageing

ROPERTIES sulating material toc current

Dielectric streng

gth

2.Dielectric Constant:The dielectric constantan insulating material toenergy.It varies with temperatfrequency.

: t measured the ability ofo store electrostatic ture, humidity and

3.Dissipation FactorRatio of total power lomaterial of the product ocurrent in a capacitor indielectric. It varies over a frequeand temperature etc.

r:oss in watts, in theof the voltage and which the material is aency range, moisture

4.Insulating ResistancThis is the ratio of voltacurrent flowing in the ba

ce:age applied to thease laminate.

5.Surface Resistance:It is the resistance to lethe surface of an insulatiThe surface resistivity d•surface humidity,•surface cleanliness• surface finish• presence of chemicallysurrounding atmosphere

eakage current along ing material. depends ony active agent in thee and temperature.

6.Volume Resistivity:Volume resistivity is the mleakage current through thematerial.

measured resistance toe body of an insulation

7.Water absorptionLaminate absorbs moiswhen expose to high hum Thin laminate absorbsaffect the Electric proper

sture to some extent,midity condition.s moisture adverselyrties.

2.2.2 PHYSICAL PROPE1.Water Absorption:The amount of water aspecified size immersedspecified period ( Generaspecified temperature (e water absorption in m orpercentage of increase o

ERTIES:absorbed by a sample of in distilled water for aally 24 hours) at ae.g., 20 to 25°c)milligramsover the initial weight.

2.Flexural Strength:This is a measure of thwhich a laminate strip wfracture, when supportethe center.The values differ in twoparallel to the length of fperpendicular to it (crossThe cross wise values a

he force per unit area,with stand withouted at ends and loaded in o directions e.g., filler (length wise) and s wise). are in most cases lower.

3.Thickness:The extent of manufacturing tcontrol within limits is of particuPCBs are used with edge conne

thickness variation and its ular significance when theector.

4.Warp and Twist: The Warpage along thtwist is the warpage alonExcessive warpage or tat various stages of PCB

he edge of a sheet andng the diagonal.twist presents problems making and assembly.

5.Flame Resistance:When a laminate is in conspark, it gets hot enough topolymer structure.This develops voids. The rapid oxidation of theflames.The reaction produce heaburning.

ntact with a flame or ao cause a breakdown of the ese free radicals producesat, further laminate

6.Punchability:Punching is the simplest aproducing complex shapes fGood punchability means•no cracking•no lifting around the punch• smooth edges and smooth

and quickest method offrom the laminate sheets.shed holeshness inside holes

2.3 Types of Lamin 1.Paper Phenolic: Consists of a solution of reacformaldehyde in a solvent. Phenolic resins are reinforceclad laminates.

natesction product of phenol anded with paper fillers for copper

2.Epoxy Laminates: They are an important raresins. Epichlorohydrin and a bivto give the base resin.

apidly growing class ofvalent phenol are reacted

Advantages:•Low shrinkage•Toughness•High mechanical streng•Chemical resistance (Ac•Water resistance (low w

gthcid, Alkali & Solvent)water absorption)

Commonly used varieties ofin NEMA standards are,FR-3 - Paper Epoxy (FirFR-4 - Glass Epoxy (FireFR-5 - Glass Epoxy (FireG-10 - General purposeG-11 - Glass Epoxy (Tem

f epoxy laminates as listedre Resistance)e Resistance)e & Temp. Resistance)e Glass Epoxymp. Resistance)

3.Polyester Laminates Polyesters are solutions oresins in copolymerisable metc. they are exclusively usedreinforcement.

s: of unsaturated polyestersmonomers such as styrene, d with glass fiber

Advantages:•possess good arc and tresistance•dimensional stability• water resistance

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4.PTFE Laminates: Poly Tetra Fluro Ethylene is areinforced with glass, results in Advantages• low dielectric constant• low dissipation factor underhumidity and frequency range.• The Dielectric strength is ver• excellent electrical insulationconditions.

a thermoplastic, which when a laminate.r a wide temperature,ry highn under severe environmental

4.Silicon Laminates: A small portion of copper clasilicon resins with Glass reinforc Silicon resins contain silicon,The glass based laminates haveperiod and at higher temperatu

ad laminates are made ofcements. , carbon, oxygen and hydrogene up to 250°C for an extendedure for short periods of time.

Advantages:•Good heat resistance•excellent arc resistance• good electrical properties

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5.Melamine Laminate Melamine resins can be creinforcing fillers but best pglass fabric is used. The most significant proplaminates is a high arc resist GM-Glass Melamine vari A major disadvantage ofis the poor dimensional stab

es: combined with a variety ofproperties result whenperty offered by these tance.iety Melamine Glass Laminate bility.