PCB_MF

5.4 PARTICULATE MATTEWater rinsing and the blousually remove only the loofor the thorough cleaningwet brushing is recommend

ERS:owing with compressed airose particle.g of particulate matters,ded.

5.5 VAPOUR DEGREASINLaminate copper surface iremoves the oil and soil (suand salts) contaminates fromEg.trichloroethylene and pe

NG: is vapour degreased anduch as oxides, hydroxides m the surface.erchloroethylene.

5.6 MECHANICAL CLEANMechanical cleaning operwhen the boards have beenscrubbing process only on wduring wet sanding with 2 water resistant abrasive p scrubbing abrasive fiber ro

NING:ration being with sandingn drill or with abrasivewet condition.280-600 grit paper is used oller are used





5.7 CHEMICAL CLEANING:Concentrated alkali chemthe oil or grease particles on

micals are used to remove n the surface of laminate.

UNIPHOTO P

IT 6PRINTING









PHOTO PRINTcoating of photo resist (liqlaminate surface

TING quid or dryfilm) on the

6.1 LIQUID PHOTOorganic liquids which wheproper wavelength are chemsolubility of certain solventThere are two types:1) Negative Acting2) Positive Acting

O RESIST: en expose to light of the mically changed the (developers).

1.Negative Acting:It is initially solvable (beforedeveloper, but after exposinand insoluble in developer.2.Positive Acting:It is opposite to Negative It is initially not solvable iexposing initially not solubleexposing polymerized positdevelopers.

e exposing) in theng it becomes polymerized acting.in developer, but aftere in developer, but aftertion become soluble in

6.2 Negative Acting DryfilmIt is first soluble in its devit becomes polymerized, andeveloper.Normally dryfilm photo rethickness are available,

m Resist:velopers and after exposingnd not dissolved in esists from 12.5µ to 75 µm.

PROCESSING:Cleaning :a) Degreasing in Trichlorob) Abrasive cleaner scrubc) Thorough cleaner rinsed) Blow dry with clean aire) Oven dry 50-60oc, 10-1

oethylene vapour (pumice)e (No residue)r15mins

Surface coating :Spray or dip coating (Liquusing heat and pressure (drmachine.If it is dryfilm resist, durinpolyethylene/polypropylene

uid photoresist) or laminateryfilm photoresist) throughng this process the e coversheet is removed.









Prebaking and norLiquid phtotoresist after cdry at 45oC to 75oc in air cirwell ventilated for 15 to 20Dryfilm photoresist after lcooled between 10-15min fstability called normalizing p

rmalizing :coating immediately ovenrculating type oven which is mins. lamination immediatelyfor better dimensional period.

6.3 Exposing :Registration of the photogside) onto the polyester she the two are then placed iintimate contact between sThe proper exposing time the light intensityTemperaturephotopolymer typethickness and type of equi

graphic film (emulsioneetin a vaccum frame forsurface.e will depend uponipment being used





6.4 Developing Developing afterstarts with the peeling of thcover sheet. The developingthe photoresist used.

gr stabilization (1-15 mins)he protective polyesterg solution depends upon





Post Baking :Baking after developing a40oC and 60oC for 10 mins.The chemical resistance is

at temperature betweens enhanced by baking.

Etching:After post baking the circu Etching can be done usinor other common Acid mixt

uit going to mild ething.ng ammonium persulphatetures.

6.5 Rinsing:Thorough rinsing and inand rinsing is needed.

some cases scrubbing

6.6 Drying :Blow dry with filtered Air

r