Printed Ckt Board Types of PCB

(I) Single Side (II) Double Side (III) Multi Layer

(V) Flexible PCB

* Single Side ( 1 layer ) :- The insulating substrate contains ckt pattern on

only one side. Which is called as solder side. The other side is called component side.

* Double Side (2 layer) :- Double side means the ckt pattern is present on the either side of the insulating material ckt pattern both on component side & solder side.

* Flexible Cards :- Flexible boards are similar to rigid boards except the board are made from a flexible substrate material. The base materials are very thin and the common thickness is 0.1mm.

* Multi layer Board (MLB, 4L,6L,8L,12L,16L ) :-

The ckt density is high compare to D/S for inner layer

made of special laminate is used for bonding purpose ( Prepreg). The inner layer is etched “CU” and outer layer is Non- etched ckt. After lamination or pressing

the boards are drilled and plated like PTH D/S.

Process Flow chart for Single Side P.C.B.

Sheet Cutting Film master preparation Screen Preparation

Drying Screen Printing Board cleaning

Retouching Etching Drilling Ink Stripping

Legend Printing Roller Tinning or HAL Masking

Final Cutting Q.C.

Process Flow Chart of Double Side P.C.B.

Sheet Cutting Film Master Preparation CNC Drilling

Photo Printing PTH or Electroplating Board Cleaning

Pattern Plating or Electro Plating Dry film Stripping Etching

H.A.L. Green Masking Tin Stripping

Legend Printing Final Cutting Q.C.

Mechanical Operation

* Sheet Cutting :- Measure the size of PCB from film or Artwork.

W

L

* Board Area Panel Sz.

PCB Sz.

Boarder Area

* Laminates or Copper Sheet :-

1. Glass Epoxy 2. Paper fenolic 3.Teflon 4. Ceramick (CEM)

* Glass Epoxy :- Thickness S/S 1.6 35/0 Cu Thickness

Insulating Material thickness

D/S 0.8-18/18

1.6-18/18

2.4-18/18

3.2-18/18

Base material is reinforced with glass fiber or paper fiber as filler and epoxy resin and the cu foil is pressured over it to get cu clad laminates.

* Paper Phenolic :- Phenolic laminates are reinforced with paper fillers and the cu foil is pressed to the base material.

Thickness :- Fr-2, C-8000, 1.6- 35/0------ S/S, 0.8-18/18--- D/S

1.6- 18/18-----D/S

* Teflon Laminates :- Teflon is reinforced with glass fiber to get a laminates of low dielectric constant and it is used in Radio frequency.

* SHEARING MACHINE :- Used for laminate cutting for PCB production.

* Manual Shearing * Motor drive Shearing.

* Final Cutting i.e. cutting in finish size.

* Shearing Blades :-Two Blades :- (I) Fixed Blades

(ii) Movable Blades.

* Punching :-Making Big hole, slot of different shape Die &Punch.

1 to 1.50

* Blanking :- Clean Cutting operation is done with a punching tool.

* Routing :- Final Cutting by CNC machine or Pin router

* Drilling :- (I) Manual Drilling (ii) CNC Drilling ( Computer numeric Control)

* Manual Drilling :- * Used H.S.S. Drill Bit* Speed of M/C is 6,000-16,000 RPM* Stack Drilling* Jig Drilling.

CNC Programming & Drilling (I) Do path making(II) Focus the Hole with help of camera and monitor.(III) For time saving and maintained the accuracy.(IV) After programming Drill one Panel for checking the program.(V) Checked Missing Hole, Extra Hole,Shifting, Inter changed Hole, Drill Dia (

Drill dia checked by Hole Gauge. )

T3 T2

T1 Path Making

* Drill Bit :- Tungsten Carbide drill bit used in CNC machine.

Shank dia

* In double side PCB drill dia is always 0.1mm extra from finish size.

3.175

*. Ink Stripping/ Dry film :-

To remove the ink by using Naoh or Koh solution.Ink remove and the cu appears on track and pads only.

Masking

(I) Thermal Masking (II) PISM ( Photo Imagable solder Mask)# Thermal Masking :-

*. Using Screen Printing.

*. -ve Masking film used in thermal masking.

*. Ink in paste form added Hardener and masking reducer for making liquid form.

# P.I.S.M.:- * Using Photo Printing Method.

* + ve Masking film used in PISM.

* Panel coated with PISM ink.

* Dry in oven or UV Light.

* Panel develop in Na2co3 solution.

# Peel off Test

#. To cover the panel with insulating ink.

#. To protecte the cu for oxidation

# To avoid the short ckt.

Brushing (Surface Preparation) To remove the dust particles and oxide layer from the surface of panel.

.*. Chemical cleaning *. Mechanical cleaning

* Chemical Cleaning :- Using Alkali chemical to remove oil, grease & soil particle on the surface of laminates.

* Mechanical Cleaning :- Laminate Drilling Deburing (320 grid brush)

Water rinse Buffing (wet condition ) Water rinse

Drying (with hot blow air )

FILM MASTER PREPARATION* High efficiency Compact camera used for reduction and inlargement purpose.

Material Used :- (I) Lith film (ii) Lith film Developer

(iii) Sodium Thosulphate (iv) Developing Trays

(v) Retouching Ink (vi) Retouching Brush

(vii) Butter Paper

* Art Work :- (I) Manual Artwork (ii) Take Design Print out

* Lith film Developer :- PART- “A”(P-Methyl amino phenol sulphats PART- “B” ( Sodium Carbonate ) Temp.- 200 +-

-30c

* Fixer :- Sodium Thosulphate

* Retouching :- Using Opaque ink for cover the pin holes.

SCREEN PRINTING

It is done with the help of a wooden/ Aluminum frame having apolyester cloth tightened over it. Polyester is available in different meshes. Which are indicated by “T” that indicate the number of thread gapping.

Wooden frame

Three methods for Screen Printing :-

(I) Direct Method :- Ammonium dichromate or Potassium dichromate is mixed with super coat solution in 1:3 ratio.

(II) Indirect Method :- Using Five Star film.

* Film Develop in H202 (Hydrogen Peroxide Solution )

(III) Direct-Indirect Method :- Chromaline film is used.

* Printing Ink :- Acid Resist Blue ink for Printing of Single Side PCB.

* Squeegees :- The sharpness of the squeegees is very important for printing. Line sharpness. Uniform ink coating thickness and the edge definition depends on the squeegees sharpness.

ETCHING

(1)Immersion (2) Bubble (3) Splash (4) spray Etching

* Ferric Chloride Etching SolutionFecl3 350-500 g/ltr

HCL 60 to 65 ml/ltr

Temp 200c to 300c

Cu +Fecl3 Fecl2 +Cucl (Green Color )

* Chromic Sulfuric Acid Etchant

Chromic AcidH2so4Temp

200 to 240 g/ltr

60 to 65 ml/ltr 20 to 300 c

* Ammonium Chloride Etchant

Ammonium BicarbonateAmmonium NitrateCupric ChlorideAmmonium ChlorideTemp

75g/ltr80g/ltr200g/ltr100 to 110g/ltr45 to 55oC

* Etching Problems1- Under Cut

2- Over Hang

Over Hang :- Excess metal growth on the side of the lone is

called over hang.

* ( Used in Spray Etching )

Electrolyses/ P.T.H (Plated Through Hole):-

The Copper will be deposited on hole wall without electricity.

* With the help of chemical reaction

* 2 to 5microne Cu ( Deposit on hole wall)

Most important process in double Side PCBs

Process of Electrolyses

1- Debarring

Drilled panel are cleaned using debarring machine which uses a 320 grade silicon carbide brush.

2 - Alkaline Soda Cleaning:-

Ginplate CC-50 5% by volume

D. I. Water 50%

Temp. 26 to 70oC

W. R. 1- 2 Min.

3 - Micro Etch:- Ginplate Ad-481 120-150gm/l

D. I. Water To make one ltr.

H2SO4 5cc /ltr.

Time 2-5Min.

W.R. 1Min.

4 - Pre-Activator The function of this bath is to initiate the reaction of catalyst.

HCL 30%

Remain Water D. I. Water

Time 1min. 5- Activator

Gin plate -additive 443 5ml/l

Ginplate activator 76ml/l

Time 5-6 Min.

The function is to activate the entire surface including metal and base.

6- Post Activator Gin Plate PA-491Remaining

17%

D.I. Water

Its function is to remove stannic layer and to increases the bonding of electrolyses cu and ensure uniform bonding.

*. Gin Plate Cu 406A

*. Gin Plate Cu 406B

*. Gin Plate Cu 406CWaterTime

100ml/ltr100ml/ltr10ml/ltr

D.I. Remaining10-12 Min.

PHOTO PRINTING

# Lamination :- Laminted the D/S Panel with P.P.D.F.R. Film(Phto Polymer Dry Film Resist ) (1.0,1.5,2.0 mils) Release Sheet of 1.0mil, Polthin 1.0mils

#. Normalizing

#. Expose in U.V. Light, used +ve Pattern (ckt) film in D/S

#. Develop in Na2Co3 Solution , Take -ve image on Panal

#. In S/S PCB -ve ckt film is used for mfg. Of S/S PCB

#. Temp- 110-115 0c

Electro Plating(1) Cu Plating (2) Tin Plating

* To increase the cu thickness of hole wall.

H2So4

CuSo4 Cupper acid

Current

TimeAnode

Anode Bag

10%

80g/l7cc/l

2-3 Amp/Sq.dm

15minCu. Min-0.04-0.08%

Polypropylene

Anode Hook Titanium or

Stainless Steel

Bath Tank P.v.c.

*. Tin Plating

Stannous Sulphate

H2So4

Stannous Carrer Additive

Stannolume Brighter

Time

Anode Current

Anode

30g/l

100ml/l

30ml/l

2ml/l

5min

1-2 Amp/dm2

60% Tin &40% Lead

*. Legend Printing or Back Marking

Used for identification of holes for which component can be placed .Screen Printing method for Back marking

process.

*. Roller Tinning Or Hot Air Levelling ( H.A.L.)

To avoid the oxidation layer on Pads

# Flux ( Liquid)

# Sn+Pb ( Tin+ Lead) 60+40#. Temp- 2300c to 2500c

*. Final Cutting ( Routing) To Cut the PCB in exact Size ad required by

the customer.

Quality Control

(I) Checking for short ckts.

(II) Checking for shifting

(III) Checking for required hole dia.

(IV) Checking for the proper masking.

(v) Checking for final cut and above all whether the PCB is delivered in the same material as desired or not