pcb production methods

8/6/2019 Pcb Production Methods

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What is PCB? A printed circuit board, or PCB, is

used to mechanically support andelectrically connect electroniccomponents using conductive

pathways, tracks or signal tracesetched from copper sheets

laminated onto a non-conductive

substrate.

It is also referred to as printedwiring board (PWB) or etched wiringboard.

A PCB populated with electroniccomponents is abbreviated as

printed circuit assembly (PCA), alsoknown as a printed circuit boardassembly (PCBA).


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History of PCB:

The inventor of theprinted circuit was theAustrian engineer Paul Eislerwho, while working inEngland, made one circa 1936

as part of a radio set.

Around 1943 the USAbegan to use the technologyon a large scale to makeproximity fuses for use inWorld War II.

After the war, in 1948, theUSA released the inventionfor commercial use.


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Before printed circuits (and for a while

after their invention), Point to point constructionWas used.

The resulting devices were prone to fail from

corroded contacts, or mechanical loosening

of the Connections and others.

For prototypes, or small production runs,

wire wrap or turret board was more efficient.

But complexity of circuits, loosening of contcts

Again raise a problem.


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Invention ofPCB Came up with a new era open for

technical world.

Originally, every electronic component had wire

leads, and the PCB had holes drilled for each wire ofeach component.

This method of assembly is called through-holeconstruction.

United States Army Signal Corps developed the

Auto-Sembly process in which component leadswere inserted into a copper foil interconnectionpattern and dip soldered.

With the development of board lamination andetching techniques, this concept evolved into thestandard printed circuit board fabrication process inuse today and further automatic soldering

process(Wave Soldering).


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Motivation:

Understanding underlying manufacturingprocesses is almost always important for anengineer:

Allows the design to exploit capabilities; and Ensures that the design will be manufacturable.

PCBs have been produced for many years;

advances with technological improvementsare notable.


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Typical PCB Manufacturing

Process:

In this section, we will look at some of the

equipment and processes that is used inmodern PCB production.

Although Steps description vary person to

person but we tried to present a most generalProcess flow.


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Each development stage is carried

out by a dedicated piece ofequipment which may form part of

an assembly line.

Depending on your application, note

that some stages may be missing

here. For instance, a tinning stage is

often included after etching to reduce

copper layer oxidation. A multi-layer

PCB, too, requires a lamination

stage to join the layers.


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Holes through a PCB are typically drilled with small-diameterdrill bits made of solid

coated tungsten carbide.

The drilling is performed by automated drilling machines with placement controlledby a drill tape ordrill file.

These computer-generated files are also called numerically controlled drill(NCD)files or "Excellon files.

The Excellon format is similar to the IPC standard IPC-NC-349 format[2]

. TheExcellon format is used to rout data between CAD/CAM systems as well as to driveCNC machines. The Excellon format was designed for and is suited for driving aCNC machine. (There as some issues about specifying the coordinate formatthough.) .

The drill file describes the location and size of each drilled hole. These holes areoften filled with annular rings (hollow rivets) to create vias. Vias allow the electricaland thermal connection of conductors on opposite sides of the PCB.

When very small vias are required, drilling with mechanical bits is costly because of

high rates of wear and breakage. In this case, the vias may be evaporated by lasers.Laser-drilled vias typically have an inferior surface finish inside the hole. Theseholes are called micro vias.

Source: http://www.megauk.com accessed 12 Feb 2008

Drilling


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PLANECLEARANCE

HOLE

CAPTURE

PADS

TRACE

HOLE

SHADOW

SHADOWHOLEPLATING

The PCB assembler works with finished hole size.The fabrication process is based on the drilled holesize. Along with all of this, it is necessary to size holesin such a way that the power planes of the PCB arenot degraded by placing holes so close together thatthey cause slots to be created in the planes byoverlapping clearance holes. It is not possible tospecify generously large hole sizes and insulationspacing to make manufacturing or fabrication easy

without risking degradation of the environment neededby the high speed signals travelling across those

planes through the PCB.

CROSS SECTIONOF A PLATED THROUGH

HOLE

Plating of Holes


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Finished hole size

Drilled hole sizeCapture pad

Clearance holeHole shadowManufacturing toleranceHole platingCopper foil

Annular ring

IMPORTANT DIMENSIONSFinished hole diameterdrill size minus copper plating.

Drilled hole diameter- finished hole diameter pluscopper plating

Hole shadow- drilled hole diameter plus manufacturing

tolerance.Capture pad- hole shadow plus annular ring allowance

Clearance pad- hole shadow plus insulation gap.

Thermal Ties


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A laminator is used to apply the Film .

By carefully monitoring both pressure magnitude and

distribution within your lamination rollers, with pressure indicatingfilms, wrinkling induced defects can be significantly reduced.Over tightened or loose or worn roll chucks can cause rollermisalignments and imperfect nips - both of which are the primarycontributors to intermittent wrinkling.

Film Lamination

Always use good quality pre-coated Positive photoresist

fiberglass (FR4) board.


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UV units used to expose the photoresist on a PCB.

UV Exposure

Inner View of UVExposure Machine

Standard fluorescent lamp ballasts and UV tubes are

used in maschine.

For small PCBs, two or four 8 watt 12" tubes will be

adequate, for larger(A3) units, four 15" 15 watt tubes

are ideal.

A timer which switches off the UV lamps automatically

is essential, and should allow exposure times from 2 to

10 minutes in 30 second increments.


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1 UV Exposure Process 2

3

4

5


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There are many different sorts of etching, developing, and strippingsetups. A unit that sprays the chemicals over board panels, mounted

inside.

Different units (of the same type) are typically used for each stage

described, above.

A panel that is inserted into a spray tank

Etching

board is submerged in etching solution such as ferric chloride.

Splash etching uses a motor-driven paddle to splash boards

with etchant.

In spray etching, the etchant solution is distributed over the

boards by nozzles, and recirculated by pumps.

As more copper is consumed from the boards, the etchant

becomes saturated and less effective


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Stripping:

Board Strippers:

Stripper L10: This sulphuric acid based immersion-stripping solution is formulated for the stripping of nickel

and tin from copper and brass without attack on the base materials.

Alstrip 98LC: A one-step stripper for tin-lead, based on stabilized nitric acid, it gives a high stripping speedand high yield There is low attack of the copper surfaces, which are always perfectly bright, even after repeatedpasses through the stripping machine.

FilmStrippers:

Remover DFA95LC: A stripper for aqueous dry-films suitable for fine-line PCBs manufacturing, eliminatingthe dry-film residues even in recessed areas or when over lapping occurs.

Jig Strippers:

Stripper L30: 1 :-The first version L30/1 is used for the immersion stripping of tin and tin-lead deposits fromcopper.

2:-The second, L30/2 is used for the stripping of tin, tin-lead and copper deposits from stainless steel jigs andcontacts.


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Solder masking:

Solder mask or solder resist is a lacquer-like layer of polymer that provides a permanent protective

coating for the copper traces of a printed circuit board (PCB) and prevents solder from bridgingbetween conductors, thereby preventing short circuits.

Solder mask was created primarily to facilitate wave soldering used in mass assembly and

traditionally it was of green color.

The lowest-cost solder mask is epoxy liquid that is silkscreened through the pattern onto the PCB.

Liquid Photoimageable Solder Mask (LPISM): Now a days advance method of PCB fabricationprocess uses LPISM .

There are currently four main categories of photo imageable solder mask application:

1.Screen print: Applied to the PCB with a squeegee blade through a tensioned mesh.

2.Curtain coat: LPISM is applied as the PCB passes through a curtain of low viscosity (


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Silk Screening:

Line art and text may be printed onto the outersurfaces of a PCB by screen printing.

space permits, the screen print text can indicatecomponent designators, switch setting requirements,test points, and other features helpful in assembling,testing, and servicing the circuit board.

The toner image will transfer to both the baselaminate (fiberglass or CEM) and the circuit traces.

After this image is transferred in the usual way, theWhiteTRF foil is added over the black toner the sameway the GreenTRF was applied to the circuit image.

Note that the image is printed in reverse (mirrored)because it will be put on the top of the SMT board.

Run it through the TI

A laminator device to fuse thewhite to the toner image.


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Populating and Soldering:

Once a board is created, it is still necessary tostuff the board with components.

This can be done by hand, but in mass-production time is an issue.

Automation includes few very effective process

comprises both readiness and reliability discussedin the next section.


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Soldering Methods:

There are two typical ways that a board hascomponents soldered onto it:

1. The Reflow method where solder is applied to theboard in a paste form, the components are addedand then soldering is performed in an oven; and

2. The Wave soldering method sees the components

added, and then passed over a standing wave ofsolder to perform the soldering.


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A reflow oven:

Temperature Profile:


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Each of the two methods has advantages anddisadvantages:

Some parts cannot handle the thermal shock experienced bybeing passed through molten solder;When wave soldering is used, it is necessary to hold

components in place: glue!Wave soldering is FAST!Reflow soldering does not really work with through-hole parts.

Regardless of the method used, particulartemperature profiles must be adhered to.


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To place components on a PCB, a Pick andPlace unit can be used.

Again, component placement informationoriginates from the CAD package.

An interesting home-brewed solution that showsmany of the necessary steps in this process is at:Homebrew Surface Mount Pick and Place Taig Mill Conversion

Pick and Place Units:


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PART- 2

DESIGNING OF CIRCUIT


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Introduction: Now it's time to turn it into a nice Printed Circuit Board (PCB) design.

For some designers, the PCB design will be a natural and easy extension of the design process. But

for many others the process of designing and laying out a PCB can be a very daunting task.

This Presentation is presented to hopefully take some of the mystery out of PCB design.It gives

some advice and rules of thumb on how to design and lay out your PCBs in a professional

manner.

There are many basic rules and good practices to follow, but apart from that PCB design is a highly

creative and individual process.It is like trying to teach someone how to paint a picture.

Indeed, many PCB designers like to think of PCB layouts as works of art, to be admired for their

beauty and elegance. If it looks good, itll work good. is an old catch phrase.


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PCB Packages:

There are many PCB design packages available on the market, a few of which are freeware,shareware, or

limited component full versions.

Professionals use the expensive high end Windows based packages such as 99SE and DXP.

Hobbyists use the excellent freeware DOS based Protel AutoTrax program, which was, once upon

a time, the high-end package of choice in Australia.

There is however, one distinct exception. Using a PCB only package, which does not have

schematic capability, greatly limits what you can do with the package in the professional sense.

Generally good PCB packages are provided with some hot keys for direct unit conversion.


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The Old Days:

Back in the pre-computer CAD days, PCBs were designed and laid out by hand using adhesive

tapes and pads on clear drafting film.

Many hours were spent slouched over a fluorescent light box, cutting, placing, ripping up,and routing tracks by hand.

Those days are well and truly gone, with computer based PCB design having replaced this

method completely in both hobbyist and professional electronics. What used to take hours can now

be done in seconds.


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Standards:

There are industry standards for almost every aspect of PCB design.These standards are

controlled by the former Institute for Interconnecting and Packaging Electronic Circuits, who are

now known simply as the IPC.

The major document that covers PCB design is IPC-2221, Generic Standard on Printed Board Design.Thisstandard superseded the old IPC-D-275 standard (also Military Std 275) which has been used for the last half

century.

Local countries also have their own various standards for many aspects of PCB design and manufacture, but by

and large the IPC standards are the accepted industry standard around the world.

Even today work on generalization of one standard world wide is going on. Hope fully soon it will be a onestandard further.


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The Schematic:

Before you even begin to lay out your PCB, you MUST have acomplete and accurate schematic diagram.

Many people jump straight into the PCB design with nothing

more than the circuit in their head, or the schematic drawn on

loose post-it notes with no pin numbers and no order.This just

isnt good enough, if you dont have an accurate schematic then

your PCB will most likely end up a mess, and take you twice as

long as it should.

Garbage-in, garbage-out is an often used quote, and it can

apply equally well to PCB design.

A PCB design is a manufactured version of your schematic.

Good practice will have signals flowing from inputs at the left to

outputs on the right.

Electrically important sections should drawn correctly, the way

the designer would like them to be laid out on the PCB. Like

putting bypass capacitors next to the component they are

meant for. Little notes on the schematic that aid in the layoutare very useful.

Notes not only remind yourself when it comes to laying out the

board, but they are useful for people reviewing the design.


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Working to Grids:

The second major rule of PCB design, and the one most often missed by beginners, is to lay out

your board on a fixed grid.This is called a snap grid, as your cursor, components and tracks will

snap into fixed grid positions.

100 thou is a standard placement grid for very basic through hole work, with 50 thou being a

standard for general tracking work, like running tracks between through hole pads.

Why coarse snap grid so important? Its important because it will keep your components neat and

symmetrical; aesthetically pleasing if you may.Its not just for aesthetics though - it makes future

editing, dragging, movement and alignment of your tracks, components and blocks of

components easier as your layout grows in size and complexity.

Good PCB layout practice would involve you starting out with a coarse grid like 50 thou and using

a progressively finer snap grid .If your design becomes tight on space drop to 25 thou and 10

thou for finer routing and placement when needed.

A good PCB package will have hotkeys or programmable macro keys to help us switch betweendifferent snap grid sizes instantly, as we will need to do this often.

There are two types of grids in a PCB drafting package, a snap grid as discussed, and a visible

grid.The visible grid is an optional on-screen grid of solid or dashed lines, or dots.This is displayed

as a background behind your design and helps you greatly in lining up components and tracks.


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Some programs also have what is called an Electrical grid.This grid is not visible,but it makes your cursor snap onto the center of electrical objects like tracks andpads, when your cursor gets close enough.

One last type of grid is the Component grid.This works the same as the snap grid,but its for component movement only.This allows you to align components up to adifferent grid.


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Tracks:

There is no recommended standard for track sizes.

Every design will have a different set of electrical requirements

which can vary between tracks on the board.All but basic non-

critical designs will require a mixture of track sizes.

The lower limit of your track width will depend upon the

track/space resolution that your PCB manufacturer is capable of.

For example, a manufacturer may quote a 10/8 track/space figure.This means that tracks can be no less than 10 thou wide, and the

spacing between tracks (or pads, or any part of the copper) can be

no less than 8 thou.

The IPC standard recommends 4thou as being a lower limit.

As a guide, with home made PCB manufacturing processes likelaser printed transparencies and pre-coated photo resist boards, it

is possible to easily get 10/10 and even 8/8 spacing. Changing your track from large to small and then back to large

again is known as necking, or necking down.This is often

required when you have to go between IC or component pads.This

allows you to have nice big low impedance tracks, but still have theflexibility to route between tight spots.


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In practice, your track width will be dictated by the current flowing through it, and the maximum

temperature rise of the track you are willing to tolerate. Remember that every track will have a

certain amount of resistance, so the track will dissipate heat just like a resistor.

The thickness of the copper on the PCB is nominally specified in ounces per square foot, with1oz copper being the most common. The thicker copper layers are useful for high current, high

reliability designs.

As a rule of thumb, a 10degC temperature rise in your track is a nice safe limit to design

around.

Pads:Pad sizes, shapes and dimensions will depend not only upon the component you are using,

but also the manufacturing process used to assemble the board, among other things.

There is an important parameter known as the pad/hole ratio. This is the ratio of the pad size to

the hole size.

As a simple rule of thumb, the pad should be at least 1.8 times the diameter of the hole, or atleast 0.5mm larger.

Pads for leaded components like resistors, capacitors and diodes should be round, with around

70 thou diameter being common. Dual In Line (DIL) components like ICs are better suited with

oval shaped pads (60 thou high by 90-100 thou wide is common).

Most surface mount components use rectangular pads, although surface mount SO package

ICs should use oval pads.


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Vias:

Vias connect the tracks from one side of your board to another, byway of a hole in your board.

Vias are made with electrically plated holes, called Plated Through Holes

(PTH). Plated through holes allow electrical connection between differentlayers on your board ..

What is the difference between a via and a pad? Practically speaking there is no realdifference, they are both just electrically plated holes. But there are differences whenit comes to PCB design packages. Pads andVias are, and should be, treateddifferently.You can globally edit them separately, and do some more advancedthings. So dont use a pad in place of a via, and vice-versa.

Polygons: Polygons are available on many PCB packages. A polygon automatically fills in (or

floods) a desired area with copper, which flows around other pads and tracks.They are very useful for laying down ground planes.

Make sure you place polygons after you have placed all of your tacks and pads.


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Clearances:

Electrical clearances are an important requirement for all boards.Too tight a clearance between tracksand pads may lead to hairline shorts and other etching problems during the manufacturing process.

Dont push the limits of your manufacturer unless you have to, stay above their recommended

minimum spacing if at all possible..

At least 15 thou is a good clearance limit for basic through hole designs, with 10 thou or 8 thou being used

for more dense surface mount layouts.

Component Placement & Design: An old saying is that PCB design is 90% placement and 10% routing.

the concept that component placement is by far the most important aspect of laying out a boardcertainly holds true. Good component placement will make your layout job easier and give the best

electrical performance.

Every designer will have their own method of placing components, and if you gave the same circuit.

Many people like to jump straight into placing all the components into what they think is the most

optimum position on the board, all in one hit. Whilst this can work for small circuits, you dont have much

of a hope when you have more complex circuits with hundreds of components spread across many

functional circuit blocks.


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Procedure: Component placement and design

Set your snap grid, visible grid, and default track/pad sizes.

Throw down all the components onto the board.

Divide and place your components into functional building

blocks where possible.

Identify layout critical tracks on your circuit and route them first.

Place and route each building block separately, off the board.

Move completed building blocks into position on your main board.

Route the remaining signal and power connections between

blocks.

Do a Design Rule Check.

Get someone to check it.


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Basic Routing:

The longer your total track length, the greater its resistance, capacitance and inductance.All ofwhich can be undesirable factors.

Tracks should only have angles of 45 degrees. Avoid the use of right angles, and under no

circumstances use an angle greater than 90 degrees.

Point to point tracking may look more efficient to a beginner at first, but there are a few reasons

you shouldnt use it.The first is that its ugly, always an important factor in PCB design! The second

is that it is not very space efficient when you want to run more tracks on other layers.

Always take your track to the center of the pad, dont make your track and pad just touch.There

are few reasons for this.The first is that its sloppy and unprofessional. The second is that your

program may not think that the track is making electrical connection to the pad .

Only take one track between 100 thou pads unless absolutely necessary.Only on large and very

dense designs should you consider two tracks between pads.

Keep power and ground tracks running in close proximity to each other if possible, dont send

them in opposite directions around the board.This lowers the loop inductance of your power

system, and allows for effective bypassing.

Do not place vias under components.Once the component is soldered in place you wont be able

to access the joint to solder a feed through.


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An example of GOOD power routing (Left)

and BAD power routing (Right)

An example of GOOD routing (Left) and BAD

routing (Right)


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Finishing Touches:

If you have thin tracks (


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Some other Terms:

Mechanical Layer. The mechanical layer (which may go under other namesdepending on the package) is used to provide an outline for your board, and other manufacturing

instructions.It is not part of your actual PCB design, but is very useful to tell the PCB manufacturer

how you want your board assembled.

Keep out: The keepout layer generally defines areas on your board that you dont wantauto or manually routed.

LayerAlignment. When the PCB manufacturer makes your board, there will bealignment tolerances on the artwork film for each layer.This includes track, plane, silkscreen, solder

mask, and drilling.

Netlists: A netlist is essentially a list of connections (nets) which correspond to yourschematic.It also contains the list of components, component designators, component footprints


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Single Sided Design:

Single sided design can greatly reduce the cost

of your board.If you can fit your design on asingle sided board then it is preferable to do

so.

The single-sided boards are manufacturedmostly by the print and etch method.

Normally, components are used to jump over

conductor tracks, but if this is not possible,

jumper wires are used.

a single sided board design will be regarded

inversely proportional to the number of jumper

links used.


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Double Sided Design:

Double sided design can also give you the chance to make use of good

ground plane techniques, required for high frequency designs.

With two-sided boards, traces can now cross over each other,increasing density without point-to-point soldering.

Design is the two sides to interact with each other, passing signals and

voltage from one side to the other.

The hardest part of two-layer circuit is getting them to align with each

other.With efficient software package and practice this way can be

learned.


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Multi layer Design:

A multi layer PCB is much more expensive and difficult to manufacture than a single or double

sided board, but it really does give you a lot of extra density to route power and signal tracks.

By having your signals running on the inside of your board, you can pack your componentsmore tightly on your board to give you a more compact design.

Multi layer boards come in even number of layers. With 4, 6, and 8 layer being the most

common.


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Technically you can get an odd number of layers manufactured, like a 3 layer board for instance. But

it really wont save you any cost over a 4 layer board.In fact a 3 layer board might even be more

expensive than a 4 layer board because it calls for a non-standard manufacturing process.

With a multi layer board, you would typically dedicate one complete layer to a ground plane, andanother to your power.

If you have room on the top or bottom layer, you can route any additional power rail tracks on there.

Power layers are almost always in the middle of the board, with the ground closer to the top layer.

Power Planes: Using power planes can drastically reduce the power wiring inductance and impedance to yourcomponents.

A power plane is basically one solid copper layer of board dedicated to either your Ground or Power

rails, or both. Power planes go in the middle layers of your board, usually on the layers closest to the

outer surfaces.

A simple power plane will not have any tracks (or removed copper bits) at all on it, but will just be

one solid layer of copper.In which case you dont need to lay down any tracks to remove any copper.

On more complex boards we split the power plane by laying down tracks.


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Good Grounding:

Use copper, and lots of it.The more copper you have in your ground path, the lower the

impedance.This is highly desirable for many electrical reasons. Use polygon fills and planes where

possible.

Always dedicate one of your planes to ground on multi-layer boards . Make it the layer closest to

the top layer.

Run separate ground paths for critical parts of your circuit, back to the main filter capacitor(s).

stitch required points straight through to your ground plane, dont use any more track length

than you need.

Good Bypassing:

Active components and points in your circuit which draw significant switching current should always

be bypassed.

This is to smooth out your power rail going to a particular device.

Bypassing is using a capacitor.

A typical bypass capacitor value is 100nF, although other values such as 1uF, 10nF and 1nF are

often used to bypass different frequencies


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IMPORTANT FILE FORMATS


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Net List : Your PCB package can then import this netlist file and do manythings. It can automatically load all the required components onto your blank board. It can also assign a

net name to each of your component pins. With nets assigned to your PCB components, it is now possibleto Auto Route, do Design Rule Checking, and display component connectivity.

Rats Nest


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Excellon Files provide a command sequenceto a system that drills PCBs

This equipment (or its computer driver) hasan interpreter that receives and executes the

commands in sequence.

The next two slides describe the list of

commands that are interpreted.

File Formats: Excellon Drill

File:


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Source: Norme Excellon, available at http://www.forelec.ch/www/norme_excellon.htm,

accessed 12 Feb 2008.

Excellon file format is governedby ANSI/IPC-NC-349 .

% Rewind and Stop

X#Y# Move and Drill

T# Tool Selection

M30 End of Program

M00 End of Program

M25 Beginning of PatternM31 Beginning of Pattern

M01 End of Pattern

M02 X#Y# Repeat Pattern

R#M02X#Y# Multiple Repeat Pattern

M02 X#Y# M70 Swap Axis

M02 X#Y# M80 Mirror Image X AxisM02 X#Y# M90 Mirror Image Y Axis

M08 End of Step and Repeat

N# Block Sequence Number

/ Block Delete


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R#X#Y# Repeat Hole

G05, G81 Select Drill Mode

G04 X# Variable Dwell (ignored)G90 Absolute Mode

G91 Incremental Mode

G92 X#Y# Set Zero

G93 X#Y# Set Zero

M48 Program Header to first "%"

M47 Operator Message CRT DisplayM71 Metric Mode

M72 English-Imperial Mode

Snn Spindle Speed (RPM)

Fnn Z axis feed speed (IPM)

Typically, only a subset of these commands are used.


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File Formats: Excellon Drill File

Example% Reset and rewind.

M48 Start of header.M72 Imperial (English) Mode: units in inches

T01C0.0420 Tool 1 Change: to 42 mil

T02C0.0860 Tool 2 Change: to 86 mil

T03C0.0350 :

T04C0.0520 :

T05C0.1250 :T06C0.0354 :

T07C0.0280 :

T08C0.1520 Tool 8 Change: 152 mil

% End ofHeader: Drill data follows

T01 Select Tool 1 (42 mil)

X2120Y1112 Drill at (2120 mil,1112 mil): (Lots of data removed)

T08 Select Tool 8 (152 mil)

X3645Y262 Drill at (3645 mil, 262 mil)

: (Data removed)

M30 End of program.


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Gerber files are typically used to describe the copper foilpatterns on the PCB.

The interpreter idea is similar to what was describedfor the Excellon format.

Since pad shapes and track sizes need to specified, manynew commands are used.

These commands are not covered here, but a goodsource of information can be found in Gerber RS-274X

Format Users Guide, Barco Graphics,N.V.

, Gent,Belgium, 1998: available at .

File Formats: Gerber:-


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File Formats: Gerber Dated

Photoplotter


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THANK YOU

pcb production methods

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