Printed Circuit Board Manufacturing

PRIVILEGED AND CONFIDENTIAL MATERIALS

Printed Circuit Board

Manufacturing

Richard Puthota

Cookson India Ltd

December 2010


THIS DOCUMENT AND RELATED MATERIALS AND INFORMATION

ARE PROVIDED "AS IS" WITH NO WARRANTIES, EXPRESS OR

IMPLIED, INCLUDING BUT NOT LIMITED TO ANY IMPLIED

WARRANTY OF MERCHANTABILITY, FITNESS FOR A

PARTICULAR PURPOSE, NON-INFRINGEMENT OF INTELLECTUAL

PROPERTY RIGHTS, OR ANY WARRANTY OTHERWISE ARISING

OUT OF ANY PROPOSAL, SPECIFICATION, OR SAMPLE.

COOKSON INDIA PVT LTD ASSUMES NO RESPONSIBILITY FOR ANY ERRORS CONTAINED

IN THIS DOCUMENT AND HAS NO LIABILITIES OR OBLIGATIONS FOR ANY DAMAGES

ARISING FROM OR IN CONNECTION WITH THE USE OF THIS DOCUMENT.

COOKSON INDIA PVT LTD MAY MAKE CHANGES TO SPECIFICATIONS,

PRODUCTDESCRIPTIONS, AND PLANS AT ANY TIME, WITHOUT NOTICE.

Disclaimer


PCB

A PRINTED CIRCUIT BOARD PROVIDES A MECHANICAL PLATFORM FOR ELECTRONIC COMPONENTS (ACTIVE

SEMICONDUCTORS, RESISTORS, CAPACITORS, CONNECTORS, ETC.)

A PC BOARD PROVIDES 3- DIMENSIONAL ELECTRICAL INTERCONNECT FOR DEVICES INCLUDING SIGNAL, POWER,

AND GROUND CIRCUITS.

A PRINTED CIRCUIT BOARD IS SIMULTANEOUSLY AN ELECTRICAL DEVICE, A MECHANICAL DEVICE, AND A

THERMAL DEVICE.

Courtesy : Multek


UNITS MICRO INCHES MILS INCHES ANGSTROMS MICRONS MM

MICRO INCH 1 0.001 0.000001 250 0.025 0.000025

MICRON 40 0.04 0.00004 10000 1 0.001

MIL 1000 1 0.001 250000 25 0.025

MM 40,000 40 0.04 10 7 1000 1

MEASURING UNITS FOLLOWED IN PCB INDUSTRY

Capability of a PCB Manufacturer

Courtesy : Multek


PCB Process flow

Courtesy : Multek


PCB Process flow ..Confused?


PCB Value flow - simpler way

Sales CAD /CAM Engineering Plotting Inner layer

Processing

Dev/Etch/StripML LaminationDrillingDeSmearElectroless Cu


Process flow

Optional

Outer-layer

Processing

Electrolytic Cu Strip / Etch / Strip Tin

Solder mask / LP Hot-Air Leveling

Immersion GoldNC RoutingV - Scoring100% E-TestFinal Q/C

Shipping


Why Copper?

Copper is an excellent electrical conductor

Electrical resistivity is approx 1.6 micro ohm cm

An inexpensive metal

Soft and easily workable

Easily processed and patternable by photolithography, using

relatively benign chemicals


Copper Foil

Copper is the dominant metal for interconnection use.

The copper foil is normally specified by weight i.e. one half oz

per square ft (152.5 g/m2), oz per sq ft (305 g/m2).

These correspond to foil thicknesses of 17.5 and 35 microns

respectively.

It is usually produced by electrolytic deposition on a flat

mandril, and is about 99.8% pure and has a tolerance on

thickness of about ± 10%.


Copper Foil

Copper can be easily electrodeposited onto a PCB Laminate –

problems however!

ADHESION!

The adhesion is far superior from bonding copper foil sheets

by the combination of heat, pressure and adhesive.

Common adhesion tests include measurement of Peel

Strength – ‘how easy is it to peel the copper foil off’ and Pull

off Strength – how easy is it to pull up the copper foil from

the substrate


PREPREG MFG PROCESSCu FOIL MFG PROCESS

PCB Substrates Reinforcement Materials


PCB Substrates Reinforcement Materials

PREPREGS


PCB Substrates ( Laminate) MFG Process Flow


PCB Laminate MFG Process


The glass transition temperature or Tg of a polymer is the temperature at which a polymer

transitions from a glassy to rubbery state upon heating and reflects the degree of polymer

Chain motion.

Tg


Typical Dielectric Constants

Material Dielectric Constant

FR4 Fiberglass Epoxy 4.7

Teflon 2.2

Teflon Glass 2.5

Polyimide 3.5

Polyimide Glass 4.2

PCB Substrates


PCB Substrates


PCB Substrates


PCB Substrates

One important non-electrical characteristic is the maximum

temperature at which boards can be operated. This is also relevant

for the curing of printed epoxies and thick film pastes on the

boards.

Resin Reinforcement Maximum temperature 'C

Phenolic Paper 100

Glass 250

Epoxy Glass 120

Polyester Glass 120

Silicone Glass 250

Teflon Glass 200


The produced laminate boards must be robust enough to withstand

abuse during processing stages and in later life on the finished product.

Abuse can include:

Changes in temperature – sometimes rapid and hot and cold

Flexing – the boards may have to be flexed, particularly during

processing stages.

Resistance to chemicals, e.g. solvents, fluxes, acids etc.

Physical abuse – to a certain extent being dropped!

Robustness of Boards


Single Sided PCB Board Double Sided

PCB Board

Top layer has been patterned in alignment with bottom layer

Holes are drilled through board and then copper is

electrodeposited to interconnect top and bottom layers


Multilayer Boards

On multilayer boards, the individual, copper patterned laminates are stacked on

top and bottom of each other. Insulating layers between the conductors can also

be added.

Often begin with double sided board in middle and work outwards

Laminates then pressed, heated and bonded in a similar process to before.

Holes then drilled in appropriate places for subsequent electrodeposition of

copper to interconnect layers.


FLEXIBLE PCB’s

More and more interest being shown to flexible PCB’s

Applications include flexible interconnections. Advanced

applications include small screens, e.g. mobile phones – and large

‘roll up’ screens

Common substrate choices include polyester, polyimide etc.

Typical problems – flexing substrate can cause metal tracks and

components etc. to ‘peel’ off

Resistance of metal conductors can also be different when

substrate is flexed


FLEXIBLE PCB’s

Flexible circuits can reduce weight of PCB

Flexing can allow easier installation and servicing

Production can be inexpensive


FLEXIBLE DISPLAYS

Flexible Displays can take up less space (rolled up)

– more portable

Active elements can be TFT’s deposited by vapour deposition (amorphous

silicon) – also printed organic materials


Pre Clean

Courtesy : Multek


Laminate Photo Resist

Courtesy : Multek


Image & Develop

Courtesy : Multek


Etch & Strip Photo Resist

Courtesy : Multek


Prepare Target & Tooling Holes

Courtesy : Multek


AOI

Courtesy : Multek


Oxide Coating

Courtesy : Multek


Lamination Of a 6 Layer Board

Courtesy : Multek


Drill & De-burr

Courtesy : Multek


Desmear & Copper Deposition

Courtesy : Multek


Coat, Image & Develop Photoresist

Courtesy : Multek


Copper & Tin Plate

Courtesy : Multek


Strip Photo Resist

Courtesy : Multek


Etch & Tin Strip

Courtesy : Multek


Solder Mask

Courtesy : Multek


Solder Mask


Solder Mask


Solder Mask


Typical Surface Finishing Technologies


Hot Air Leveling

Air knife off-set

SolderPCB

Clamp to hold PCB


Advantage of greater thickness control in Pb Free HAL

Improved gasket sealing during solder paste

printing on fine features.

Laminate

Stencil

Sn/Pb

Lead-Free

Laminate

Stencil


Conveyorized Dip Module

Manifold

PCB

OR

Coating Chemistry Sump

CHEMISTRY

COATING

PCB

OSP Organic Solderability Preservative


OSP VISUAL INSPECTION CRITERIA

Courtesy : Enthone, Cookson Electronics


ENTEK®

OSPHASL FST

Immersion SnNi-Au AlphaLevel

Immersion AgCost Lowest Medium Medium Highest Low

Fine Pitch Excellent Poor Excellent Good Excellent

Multi Pass Medium Excellent Good Good Good

Wave OK Variable Excellent Good Poor Good

Ease of Mfr Easy Difficult Medium Difficult Easy

Warping Low High Low Low Low

Comparison of PCB Surface Finishes


ATTRIBUTES

1 1 10 9Wire Bondability

Wire Bondable = 10; Can't wire bond = 1

1 1 1

10

10

9

97

10

10

8

82

10

2

6

510

10

2

6

1

10

1

10

10

10

2

6

10

10

7

10

7

10

9

10

5

10 1 3 4 10 10 10

CO-PLANARITY(FLATNESS) Flat Pads = 10; Non Planar Pads = 1

Risk of removing Protective Coat during rework Not easy to remove = 10; Easy to remove = 1

Solderability at Wave Solde ( No prior Reflow)

Highly Solderable = 10; Least = 1

Solderability at Wave Solder (after 2-3 reflows using no clean flux)

Highly Solderable = 10; Least = 1

Cost Of PCB Fabrication Lowest Cost = 10; Highest = 1

Pin Testability of Bare Board Most Pin Testable = 10; Least = 1

Shelf - Life Longest = 10; Shortest = 1

Ionic Cleanliness Least Contamination =10; Most = 1

PROPERTY OF COPPER COATING

ALTERNATIVE COATINGS

PROPERTY COMPARISON OF ALTERNATIVE COPPER PROTECTIV E COATINGS

9 6 3 6 9

Amidazole/ Benzimidazole

Immersion Bismuth

Immersion Silver

Hot Air Solder Leveled

Rosin / Resin Coating

Benzo - Triazole

1 5 10

Electroless Nickel/Gold

5 8 10 7 7 1

Comparison of PCB Surface Finishes


Tip Plating – Apply Plating Tape

Courtesy : Multek


Solder Strip Fingers

Courtesy : Multek


Nickel Plate Fingers

Courtesy : Multek


Gold Plate Fingers & Strip Tape

Courtesy : Multek


Component Mark Printing

Courtesy : Multek


Fabrication Rout & Chamfer

Courtesy : Multek


Electrical testing checks the boards forany open or short type defects, before

shipping to the customer.

Electrical Test (BBT)

Courtesy : Multek


• For a company manufacturing electronic equipment, it is risky to depend on just

one PCB manufacturing source.

• It is important that the PCB manufacturer and the OEM / EMS are thoroughly

knowledgeable about each other’s capabilities and expectations to ensure compatibility and

cooperation.

• There can easily be differences in the perception of quality, or the documentation

package can seem inadequate to the PCB manufacturer, thus requiring additional

communication with subsequent adjustments, and inevitably, this takes time.

• Another important advantage of having a number of regular PCB suppliers is a broader

spectrum of PCB technology at the customer’s disposal.

• This can be very significant in times of great technological changes, especially when

introducing SMT, HDI (High Density Interconnect), or laser drilled boards.

Thus, the conclusion is that any OEM or EMS company should always utilize a number of approved

and regular PCB vendors.

Key Take Aways


May This Information Improve Your Ability To Weather The Storms

Education

Printed Circuit Board Manufacturing