PRACTICAL FILE

SKILLS AND INNOVATION LAB

Submitted to: Submitted by:

Vinod Kumar Name: Rohit Kumar

Asstt. Professor Roll No:210151520060

ECE Department Class: B.Tech(ECE) 5th sem

 EXPERIMENT – 1
Aim: Introduction of circuit PCB and layout tool.

Software required: Express PCB, Express SCH.

Introduction:

There are two parts to ExpressPCB, our CAD software and our board
manufacturing service. Our CAD software includes ExpressSCH for drawing
schematics and ExpressPCB for designing circuit boards. After you complete your
PC board design, we provide a low cost, high quality and fast source for having
your boards made. Here is how it works:

1. We recommend that you begin your project by drawing a schematic using

ExpressSCH. Drawing a schematic is not required, but it will save you time when
designing your board and reduce the possibility of wiring errors.

2. Next, use the ExpressPCB program to layout your PC board. If you link your
schematic to ExpressPCB, the program will guide you through the wiring process
by highlighting how the components should be connected.

3. When your layout is complete, you can determine the exact cost of having your
boards made with the Compute Board Cost command.

4. To order the boards, simply enter your name, address and billing information
into ExpressPCB and press the Send button within the Order Boards Via The
Internet dialog box.

5. In a few business days (typically 2 or 3) an overnight courier will deliver your PC

boards.

The Display:

Take a few minutes to acquaint yourself with the ExpressPCB main window, shown
below. You will notice that there are two toolbars, one along the top and another
along the left side. At the bottom of the display is a statusbar.
The Statusbar:

The statusbar shown along the bottom has three fields. The first field shows the
XY position of the mouse. The units are in inches. The coordinate (0,0) represents
the upper left corner of your board.

In the middle of the statusbar is the Snap list box. Here the snap-to-grid feature
can be turned on and its spacing set. When on, placing items such as components
and traces automatically align to the snap-grid.

The field on the right displays helpful information when you connect traces to the
pins of components. For example, the display might read: "Connecting to pin 11 of
U4" when you attach a trace to that pin.

The Side Toolbar:

The toolbar along the left side of the main window is used to select between the
different editing modes, such as place pad, place component and place trace.
Each of these modes can be selected either with the mouse or a shortcut key.

The buttons along the side toolbar are:

At the bottom of the side toolbar are 4 additional buttons that toggle on and off
features of the display:

The Top Toolbar:

The toolbar at the top of the main window has nine buttons that are always
shown:

Also displayed on the top toolbar are the following buttons. Depending on the
mode selected with the side toolbar, one or more of these may be added:
Units and The Coordinate System:

By default, the ExpressPCB program displays coordinates in Inches with the origin
(0, 0) located at the upper left corner of the board. Sometimes it can be very
useful to move the origin or to select metric units. The most common reason to
make these changes is to aid in designing a custom PCB footprint. To accurately
set the position of the individual pads of a footprint, it is frequently helpful to
move the origin to the component's center, or over pin 1. If the datasheet for a
component shows the pin spacing in metric units, changing the ExpressPCB
program to millimeters makes placing the pads very easy.

To change the display units, select either Inches or Millimeters in the Options
dialog box. Then update the Snap-to-grid spacing (also in the Options dialog) with
an appropriate value.

The (0, 0) origin can be positioned anywhere on the board. Feel free to move it as
often as you like as it only affects the display of coordinates; it does not actually
make changes to objects in the layout.

To move the origin, from the View menu select the command Set origin with
mouse. Next click on your board at the point where you want the origin to be
located. If the Snap-to-grid is on, then the origin will be positioned at a grid
location. The origin can be restored to its original position using the menu
command Reset origin to upper left.

The Grid:
Displayed in the main window is a grid of small white dots. This grid is helpful
when placing components and traces so that they align nicely. The grid is only a
display tool and will not appear on your final printed circuit board.

As you zoom out to view a large area of your board, you will notice that the grid is
not always displayed.

The grid is configurable and can be modified in the Options dialog box. You can
display or hide the grid, and also set the spacing between grid lines. The spacing is
typically set to 0.1 inches.

The Snap-to-grid is an invisible grid that is also configured in the Options dialog
box. It is very helpful when placing items to ensure that they are automatically
aligned. If the Snap-to-grid feature is turned on, pads, components and traces
always gravitate to a grid boundary when dragged with the mouse. Typically the
Snap-to-grid spacing is set to 0.05 inches (half of the Grid spacing).

The Snap-to-grid feature is most easily toggled on or off by pressing the

G key or by clicking at the bottom of the side toolbar.

Traces with Corners:

Corners allow traces to bend. They are displayed as small square blocks at the
ends of trace segments. A trace with two corners is shown here. Corners in a trace
can be dragged, inserted or deleted to change the trace's path. In your final PC
board layout, the corners will not be included.

Understanding the Layers of a PCB:

ExpressPCB manufactures double-sided boards (with 2 copper layers) and 4 layer
boards (with 4 copper layers).
Double-sided boards work well for most simple applications.They are somewhat
less expensive and take fewer days to manufacture than four-layer boards. But
four-layer boards offer advantages. They are better at controlling electrical noise
and four-layer boards can be smaller with components closely spaced together.
Also these boards are easier to lay out.

Depending on the options you choose, your boards can have as few as two layers,
or as many as seven. The layers from top to bottom are:

1. Silkscreen

2. Top Solder Mask

3. Top Copper

4. Inner Copper Ground Plane

5. Inner Copper Power Plane

6. Bottom Copper

7. Bottom Solder Mask

All boards have a Top copper and Bottom copper layer. The Top copper layer is on
the component side of the board and is displayed in red by the ExpressPCB layout
program. The Bottom copper layer is on the solder side of the PCB and is shown in
green.

The optional Solder masks layers are green coatings that cover the top and
bottom of the board. The coating is applied everywhere except over the pads
where components are soldered. These masks make soldering easier by helping to
prevent solder bridges from forming between adjacent pads and traces.

Boards with solder masks also include a Silkscreen layer. The Silkscreen layer is
used to show the outlines of components, and text identifying each part. The
outlines and text are printed on the top of the board in white ink.

Four-layer boards have two additional copper layers that are not included with
Double-sided boards. Sandwiched inside these PCBs are two inner layers, a
Ground Plane and a Power Plane. Any through-hole pad on a four-layer board can
be connected to or isolated from either of these planes. Because the inner layers
are completely filled copper planes, they greatly improve the noise immunity of
your circuit.

Beginning A New Layout:

1. Begin a new layout by running ExpressPCB. You can launch ExpressPCB from

your desktop by clicking on the icon. If you would like to design a four-layer
board, select Board properties from the Layout menu and check the 4-Layer
option.

2. In the main window is a yellow rectangle that defines the perimeter of the PC
board. You will want to change the yellow rectangle to the size of the board that
you want to make. To do this, move three of its four corners (the upper left corner
is fixed at coordinate (0,0) and cannot be moved).A corner can be moved two
ways: by dragging it with the mouse or by double clicking on it and then entering
a new coordinate. If you drag the corners, it is helpful to keep an eye on the
statusbar to determine the new dimensions of the board.

3. Now select the Default via. As you place traces, ExpressPCB may in some cases
automatically insert a via (a plated-through hole with pads) when a trace changes
between the upper and lower layers. These automatically placed vias will always
be visible. Set the size of the Default via from the Layout menu by choosing Board
properties. In the Board properties dialog box, select a value from the Default via
list box. For digital and other low power circuits, 0.048" round via is a good choice.
With our four-layer manufacturing options, we offer a very small 0.026" via,
extremely useful when designing dense circuitry.

4. If you have drawn a schematic of your circuit using ExpressSCH, link the
schematic file to your circuit board layout using the Link schematic to PCB
command found under the File menu.

5. Finally, give your board a name by selecting Save As from the File menu.
Scrolling and Zooming:

Scrolling the Main Window:

In addition to scrolling using the scrollbars, you can also scroll with the mouse and
the arrow keys. While dragging an item such as a pad or a trace with the left
button down, moving the mouse outside the main window causes it to scroll. You
can also scroll the using the keyboard by pressing the Up, Down, Right or Left
arrow keys.

Zooming In and Out:

There are four buttons along the top toolbar that are used to zoom the main
window in and out:

and then

You can zoom into a specific region of the layout by choosing dragging the
mouse. Simply enclose the area you wish to expand and center.

Placing Items in the Layout:

Placing Components- Using the Toolbar:

There are a couple of ways to place component footprints on your board. Here is
how to insert components using the toolbars:

1. From the side toolbar, select or press the C shortcut key.

2. Select the component type from the drop down list box on the top toolbar as
seen here:
There are three categories in the list:

• Favorite components: parts that you have book-marked.

• Custom components: parts that you have built.

• Library components: parts that are included with the program.

3. Select the component's orientation (rotated up, left, down, or right) by clicking

on one of:

4. Move the mouse into the main window, press the left mouse button, and drag
the component to the desired location.

5. While dragging the component, the R shortcut key can be used to rotate the
component. The + and - keys zoom in and out, and the G key toggles the snap-
togrid on and off.

6. After placing the component, assign it a Part ID (such as R1 or U2). Do this by

selecting then double click on the component to display the Component

properties dialog box.

Placing Components- Using The Component Manager:

An alternate way to place components in your board layout is to use the

Component Manager. The advantages of using the Component Manger are that it
displays a bigger window of part names; it also shows the parts in a preview
window and you can search for parts by name.
To place a component:

1. Click the button located on the top toolbar to display the Component
Manager.

2. Select one of these categories:

• Library components - Components that are included with the program

• Custom components - Components that you have drawn

• Favorite components - Components or symbols that you have book-marked

3.From the list box, choose the item to insert.

4. Select the component's orientation (rotated up, left, down, or right) by clicking

on one of the following buttons:

5. Press the Insert component into PCB button and then drag the component to
the desired location.

6. Assign the component a Part ID (such as R1 or U2). To do this, select then

double click on the component to display its Component properties dialog box.

Placing Pads:

Individual pads are used to build new components. They also serve an important
purpose as via, which are used to connect traces between the top and bottom
layers. To insert a pad:

1.From the side toolbar, select or press the P shortcut key.

2.Select a pad from the drop down list box on the top toolbar:

The list box shows the pad diameter, pad type and hole size. There are several
types of pads: round, square, surface mount and via. Square pads are typically
used on pin 1 of a component. Vias are used to pass traces between layers.
Round and via pads differ only in that ExpressPCB may eliminate a via if all the
traces connecting to it are on the same layer. If you can not find a pad the size you
need, a custom pad is easily added to the list using the Pad Manager. You can also
use the Pad Manager to add the pads you most frequently use to your favorites
list.

3. With the pad type selected, move the mouse into the main window, press the
left mouse button down and drag it to the desired location.

4. While you drag the pad, the + and - keys zoom in and out, and the G key toggles
the snap-to-grid on and off.

5.A pad or via can be connected to a Filled Plane or an inner layer power plane (of
a 4 layer board) by right clicking on the pad.

Placing Traces:

These are the steps to add traces to your layout. If you have drawn a schematic for
your circuit, be sure to read the section Linking the Schematic and PCB before you
begin.

1. From the side toolbar, select or press the T shortcut key.

2. Select the trace width from the drop down list box on the top toolbar:
A width of 0.010" is a good default for digital and analog
signals. For Vcc and Gnd power lines, use traces 0.05" or wider.

3. Select the layer by clicking on or by pressing the L shortcut key.

4. Move the mouse to the trace's first endpoint and click left. Drag the trace to the
second endpoint, then click left again. Continue placing trace segments (the L key
can be used to change layers) until you have reached the final endpoint.

5. As you drag the trace, the L key changes layers, the Del key deletes the previous
segment, the + and - keys zoom in and out, the G key toggles the snap-to-grid on
and off, the Spacebar sets the trace, and the Esc key cancels it.
6. To complete the operation, either press the Spacebar or click right.

Inserting Corners In Traces:

1. Corners (displayed as small blocks) can be inserted in an existing trace to change

its route. To insert a corner, select or press the I shortcut key.

2. Select the layer on which the corner will be placed by clicking .

3.Click on the trace where you want to add the new corner.

4.Drag the corner to the desired location.

Placing Text:

Text can be placed on the silkscreen layer or on either of the copper layers. Text
written on the copper layers will conduct electricity, so be careful not to place it
over traces or components.

Also remember that the silkscreen layer is not printed on boards when you choose
our Standard Service or Standard MiniBoard Service manufacturing options.

1. To place text, select from the side toolbar or press the A shortcut key.

2. From the top toolbar, choose the layer, orientation and the text weight (normal
or bold).

3. Select the height of the text from the drop down list box.

4. Enter your text in the text box along the right hand side of the toolbar as shown
in this example:

5. Move the mouse into the main window, press the left mouse button and drag
the text to the desired location.

6. As you drag the text, the L key toggles the layer, the R key rotates the text, the +
and - keys zoom in and out, and the G key switches the snap-to-grid on and off.

Placing Rectangles:
Rectangles are typically used make high current electrical busses, heat sink areas,
or to piece together ground planes.

To place a rectangle, select and then pick the layer by clicking on .

Next, drag the mouse to place the rectangle and set its size.

Placing Power and Ground Planes:

Filled Planes are used to add ground or power planes to a circuit. They can be
placed on either the top or bottom copper layers. They are typically drawn as a
large area that surrounds components and serve to help control electrical noise.
The outer perimeter of a Filled Plane can have the shape of any polygon and the
interior is automatically insulated from traces and pads.

To place a Filled Plane, select and then click on to choose the layer. On
the top toolbar, select the Draw filled plane option. Next using the mouse, draw a
polygon to define the perimeter of the plane. Do this by clicking the left mouse
button at each corner of the polygon, then clicking right after you have placed the
last corner. You will now notice that the polygon is filled, creating the plane, but
clearance is automatically added around traces and pads, isolating them from the
plane.

Once a Filled Plane is added to your circuit, its shape can be changed. First select
the plane with the mouse. The size of the plane can then be adjusted by dragging
the square corners. To eliminate sides of the polygon, click on a square corner,
then press the Del key. Additional sides can be inserted by dragging the circles.
Pads inside a plane can be connected to it using either a Solid or Thermal pad
shape. Connect a pad to a plane by right clicking on the pad. Then in the popup
menu, select either Top layer pad shape or Bottom layer pad shape. Lastly pick the
pad type: Thermal pad to filled plane or Solid pad to filled plane.

There may be areas inside a plane that you do not want filled. To draw a Keep out

area, select , then from the top toolbar choose the Draw keep out area in
filled plane option, along with the layer. Next use the mouse to draw the polygon
that defines the perimeter of the keep out area.

Clearance around traces and pads are automatically added inside Filled Planes.
The amount of clearance can be changed. The default values for the trace
clearance and the pad clearance are set in the Board Properties dialog box. Larger
values may be required when working with high voltage signals.

The amount of clearance for an individual trace can be set by first double clicking
on it. Then in the dialog box, choose the Custom clearance option and enter the
desired gap width.

A trace can be connected to a plane by removing the clearance gap. This is done
by placing the trace in the circuit, then double clicking on it and selecting the 0
Clearance option.
Important: After creating a plane, you will want to inspect it for these types of
problems:

1. Carefully look for areas of the plane that are too thin to be manufactured. In this
example, the plane includes a thin strip that connects the right and left thermal
pads. If any part of a plane is smaller than 0.007" the PCBs we manufacture may
not include that feature. It is up to you to ensure that your planes do not have any
copper areas with dimensions smaller than 0.007" as these areas may be
disappear when the boards are made, even though you can see them on the
screen.

2. Check your plane for "copper islands" that are not electrically connected to the
rest of the plane. This example shows pin 2 connected to the plane, but this
section of the plane is isolated from the surrounding plane.

In this case, you will want to connect islands to the greater plane using pads and
traces.

3. Sometimes tiny copper islands and thin strips are created within your filled
plane. These must be manually eliminated from your design. It is possible for
these tiny copper fragments (smaller than 0.007") to shift during the
manufacturing process, resulting in a short circuit elsewhere on your board.

Thin strips between traces are easily eliminated by increasing the Custom
clearance of the neighboring traces. Tiny islands can be removed by drawing Keep
out areas. Both of these techniques are described above.
Designing A Four Layer PCB:

ExpressPCB manufactures double-sided boards (with two copper layers) and

fourlayer boards (with four copper layers). Four-layer boards offer advantages
over double-sided. They are better at controlling electrical noise, can be smaller
with closely spaced components and are easier to layout.

Setting the number of copper layers:

Begin a four-layer design by checking the 4-Layer option in the Board properties
dialog box found under the Layout menu. This adds two inner layers to your
board, a Power plane and a Ground plane. Because these inner layers are
completely filled copper planes, they greatly improve the noise immunity of your
circuit.

Connecting To The Inner Layers:

Any through-hole pad in a layout can be connected to either the Power or Ground
internal planes. To do so, right click on the pad to connect. In the popup menu,
select one of the Power inner layer pad options to connect the pad to the Power
plane, or choose one of the Ground inner layer pad options to connect it to the
Ground plane.

Connections to the internal Power plane are displayed with a + over the pad.
Ground plane connections are marked with a - symbol.
To look at the actual inner layer planes, open the Options dialog box and check
either View Power inner layer or View Ground inner layer. Here we show what the
Power layer looks like for the example above. This example shows pins 2, 4, and
14 are connected to the Power plane. All of the other pads are isolated from the
Power plane. You will notice that pins 2, and 14 are connected to the plane with
Thermal pads, while pin 4 is connected with a Solid pad.

Split power planes and keep out areas can be placed on the inner layers. Do so by
first displaying the layer using the Options dialog box and checking either View
Power inner layer or View Ground inner layer.

To place a Split Plane, click then select the Draw split plane option on the
top toolbar. Next use the mouse to draw the polygon that defines the perimeter
of the isolated plane.

Keep out areas (a region of the inner layer that you do not want any copper) are

drawn by selecting along with Draw keepout area on the top toolbar. Then
draw the perimeter of the copper free region.

Editing The Layout:

Setting properties of an item:

Each item in your layout has specific properties. For example, the properties of a
pad include the pad type and the position of the pad. To view or change the

properties of an item, select from the side toolbar and then double click on
the item.

Moving items in the layout:

There are three ways most items can be moved. Typically, you move items by
selecting and dragging them. They can also be moved with the arrow keys by
selecting them and then pressing Ctrl-right, Ctrl-left, Ctrl-up or Ctrl-down.
Alternately, an item can be moved by changing the coordinates set in its
properties dialog box.

Moving Traces:

Traces themselves cannot be moved. The position of a trace is determined by the

straight line between the two endpoints of what it is connected to. Therefore, to
move a trace, you either need to connect it to something different, or move what
it is connected to.

Often the solution to moving a trace is to drag its corners. Several corners can be
selected at once and then dragged together. In some cases, you will want to insert
additional corners to form new bends.

To disconnect a trace and reconnect it elsewhere, select from the side

toolbar. Next, click on the trace near the point that you want to disconnect and
then drag the trace to a new pin.

Deleting items from the layout:

Deleting items from your layout is as easy as selecting them and pressing the Del
key.

Copying items:

ExpressPCB uses standard Edit commands for Copy, Cut and Paste. To copy, first
select the item or several items of interest. Next, choose Copy from the Edit
menu. Then choose Paste. The new copy will appear selected in the middle of the
window.

Copying all or Part of a PCB to Another File:

It is not possible to copy sections of a board layout between two ExpressPCB

programs running at the same time. However, you can easily copy all or part of
your PCB to another file as follows:

1.Using the mouse, select the region of the layout that you would like to copy.

2.From the Edit menu, choose Copy.

3. From the File menu, open the PCB file into which you want to insert this region.

4. Select the Paste command from the Edit menu to copy the circuit into this new
file.

Changing the Layer of items:

It is easy to move traces, rectangles and text between layers. First click on in
the side toolbar. With the mouse, select the items of interest. From the top
toolbar, click on to move the selection to the top layer; click on to move it
to the bottom.

Rotating Items 90 Degrees:

A section of a layout can be easily rotated in 90-degree increments. Do this by first

selecting the components, pads and traces of interest. Then from the Edit menu
choose Rotate Selection 90°. Repeat the command to rotate 180 or 270 degrees.

Right Click Menu:

Many editing functions can be executed from Right Click Popup menus.

Do so by clicking on an item in your layout with the Right mouse button. A popup
menu will appear with several commands listed such as Copy, Paste, Rotate, Flip,
and Set Properties.
Changing the Board’s Perimeter:

The size and shape of your board is defined by the edge markers shown in yellow.

For rectangular boards, setting the board size is as easy as setting the position of
the corners. The upper left corner is fixed at location (0,0) and cannot be moved.
The width of the board is set by moving the two corners along the right side, and
the height is set by moving the corners along the bottom.

A corner can be moved in one of two ways, you can drag it with the mouse, or
double-click on it and then enter new coordinates in the properties dialog box. If
you drag the corners, it is helpful to keep an eye on the statusbar to determine
the new dimensions.

To define more complex board shapes, insert additional edges into the board

perimeter by selecting from the side toolbar. Next, click on existing edges
where you would like to add the new corners. Drag the corners to define the
board size and shape.

Drawing on the Solder Mask Layers:

Solder mask layers are a green coating that cover the top and bottom of the board
(when you choose our Production, ProtoPro or MiniBoardPro manufacturing
options). This coating is applied everywhere on the board except over pads. A
solder mask makes assembling boards easier by helping to prevent solder bridges
from forming between adjacent pads and traces.

The ExpressPCB layout program automatically blocks the solder mask from our
library pads and components. If you want to expose other areas, do so by drawing
lines, arcs and rectangles on the solder mask layers. To draw on one of these
layers, it must first be displayed by checking View top solder mask layer or View
bottom solder mask layer in the Options dialog box. The solder mask layers are
displayed in reverse (solder mask is applied everywhere on the board, except
where something is drawn).

OTHER COMMANDS:
Linking the schematic and PCB:

The process of wiring your components together with traces can be simplified if
you link the schematic and PCB files. Typically the ExpressSCH schematic drawing
program is used to create the schematic.

Embedded in ExpressSCH schematic files are wiring lists (called NetLists) that
describe which pins should be connected together. By loading this information,
the ExpressPCB program can guide you when you place traces by showing which
pins need to be wired together.

Before linking your schematic, you will want to check it for errors. Run the
command Check schematic for netlist errors from the File menu of ExpressSCH. If
any errors are reported, correct them and then save the schematic by choosing
Save from the same menu.

Next, for every part referenced in your schematic, you need to insert the
component footprint for that part in your PCB design. Also, the Part ID values for
each footprint must be set. To learn how to insert the footprints and set the IDs,
see: Placing Components.

Now you are ready to link your schematic and circuit board. From the File menu of
the ExpressPCB program, select the command Link schematic to PCB. Here, select
the filename of your schematic.

Once linked, ExpressPCB can show you which pins should be connected together
by highlighting them in blue.

To highlight a "Net", select from the side toolbar, then click on one of the
pads of a component. This highlights the other pads that should be wired to the
pad you've selected. If the schematic has nothing connected to that pin, then no
pads are highlighted.

You can step through all of the "Nets", from first to last, to visually inspect your
PCB for missing connections. To do this select and then use these buttons on
the top toolbar to navigate through all of the nets.

Modifying Library Components:

In many cases, it is faster to build a new component by starting with a close fit
from our library. One common example is modifying a library part to use a larger
pad size. This is easily done by first inserting the library component into your
layout. Next select it with the mouse and ungroup it using the Ungroup PCB
component command from the Component menu. Now select only the pads and
then double click on one. In the Pads Properties dialog, change to the new pad
size.

Finally, regroup the component back together as described above to create the
new part. Your changes will not affect the original part in the ExpressPCB library.

Making Custom Pads & The Pad Manager:

The Pad Manager is used to create new pad sizes and to select which pads are
added to your favorites list.

Display the Pad Manager dialog box by selecting Pad Manager from the
Components menu.

You may want to add pad sizes that you frequently use to your favorite pads list.
This is done by choosing the Library Pads option, selecting the pad size from the
list box, and then pressing the Add to favorites button.

When creating a custom component, you may find that the pad you need is not in
our pad library. In this case, press the Create new pad button in the Pad Manager
to define a new pad size. Here you can create a new via, through-hole or
surfacemount pad. When designing a pad with a through-hole, the pad diameter
must be at least 0.017" greater than the diameter of the hole.

Displaying Information About a Pad:

To determine the diameter and hole size of a pad, whether it is an individual pad

or a pad in a predefined component, select from the side toolbar and click
on the pad of interest. A dialog box displays the pad information.

Exporting an Image of Your Board:

A drawing of your board showing the component placement can be exported in

three common formats: as a .BMP, DXF, or .EMF file.

To document the placement of components on your circuit board, use the Export
image of mechanical drawing command in the File menu. This command creates a
black & white image showing the pads and component outlines on the board. The
file can be saved as either a .BMP file, or as a scalable .EMF metafile.

A bitmap can also be generated using the Edit menu command Copy silkscreen
layer to clipboard.

The image can then be pasted into a Microsoft Word or other document type. To
make an image of your board for the web, we recommend pasting it into a
graphics package, then converting it to a .GIF file type.
If you work with a mechanical CAD package, you may want to import a drawing of
your board that includes the exact coordinates of each component pad. For
example, this can be very useful when designing an enclosure for your circuit
board. For this purpose, the ExpressPCB program can export a board drawing
using the common DXF format. To do this, select the Export DXF mechanical
drawing command from the File menu.
 EXPERIMENT- 2
Aim: Design Schematic of regulated DC power supply.

Software Required: Express SCH.

Theory:

An electronic circuit that produces a stable DC voltage of fixed value across the
load terminals irrespective of changes in the load is known as regulated power
supply. Thus, the primary function of a regulated power supply is to convert an AC
power into a steady DC power. Here we will design the schematic of a regulated
DC power supply using a software i.e. ExpressSCH

Procedure:

. Select the components according to the circuit diagram from the the component
manager option on the top panel.

. Arrange the components in a proper manner and then connect them according
to the circuit diagram using the wire tool on the side toolbar.

. After all the connections are made check the schematic design for errors using
the check schematic for netlist errors option, if there is an error then remove the
errors.

. Now, after removing the errors name the components accordingly and write
your name in the grid provided below and then save the file.
Final Outcome

Result: The schematic for regulated DC power supply has been designed.
 EXPERIMENT-3
Aim: Design layout (copper layer) of regulated DC power supply.

Software Required: Express PC

Theory:

Here we will design the same circuit of regulated DC power supply using
Express PCB software. This software is very much similar to the Express
SCH software, the major difference is that in Express SCH we made
connections using the normal wire but here in Express PCB we will make
connections using a copper wire.

Procedure:

. Select the components according to the circuit diagram from the the
componentmanager option on the top panel.

. Arrange the components in a proper manner and then connect them

accordingto the circuit diagram using the wire tool on the side toolbar.

. Now link the schematic design of the same circuit using the link
schematicoption available in the file option on top panel.

. Now select the highlight net connections tool on the sidebar and then
click on any point you have to connect, you will see the connections
then make the connections in this way until all connections are made.

. Try to use as much less space as you can to make the design compact in size.
Final Outcome:

Result: Layout of regulated DC power supply using copper layer has been
designed.
 EXPERIMENT-4
Aim: Introduction to Design rule check(DRC) and Netlist.

Software required: Express PCB

Theory:

Design Rule Check-

A design rule is a geometric constraint imposed on circuit board, semiconductor

device, and integrated circuit (IC) designers to ensure their designs function
properly, reliably, and can be produced with acceptable yield. Design rules for
production are developed by process engineers based on the capability of their
processes to realize design intent. Electronic design automation is used
extensively to ensure that designers do not violate design rules; a process called
design rule checking (DRC). DRC is a major step during physical verification signoff
on the design, which also involves LVS (layout versus schematic) checks, XOR
checks, ERC (electrical rule check), and antenna checks. The importance of design
rules and DRC is greatest for ICs, which have micro- or nano-scale geometries; for
advanced processes, some fabs also insist upon the use of more restricted rules to
improve yield.

Design rules-

Design rules are a series of parameters provided by semiconductor manufacturers

that enable the designer to verify the correctness of a mask set. Design rules are
specific to a particular semiconductor manufacturing process. A design rule set
specifies certain geometric and connectivity restrictions to ensure sufficient
margins to account for variability in semiconductor manufacturing processes, so
as to ensure that most of the parts work correctly.

The most basic design rules are shown in the diagram below. The first are single
layer rules. A width rule specifies the minimum width of any shape in the design.
A spacing rule specifies the minimum distance between two adjacent objects.
These rules will exist for each layer of semiconductor manufacturing process, with
the lowest layers having the smallest rules and the highest metal layers having
larger rules .

A two layer rule specifies a relationship that must exist between two layers. For
example, an enclosure rule might specify that an object of one type, such as a
contact or via, must be covered, with some additional margin, by a metal layer. A
typical value as of 2007 might be about 10 nm.

Academic design rules are often specified in terms of a scalable parameter, λ, so

that all geometric tolerances in a design may be defined as integer multiples of λ.
This simplifies the migration of existing chip layouts to newer processes. Industrial
rules are more highly optimized, and only approximate uniform scaling. Design
rule sets have become increasingly more complex with each subsequent
generation of semiconductor process.

Netlist-

A Netlist is a description of the connectivity of an electronic circuit. In its simplest

form, a netlist consists of a list of the electronic components in a circuit and a list
of the nodes they are connected to. A network (net) is a collection of two or more
interconnected components.
The structure, complexity and representation of netlists can vary considerably, but
the fundamental purpose of every netlist is to convey connectivity information.
Netlists usually provide nothing more than instances, nodes, and perhaps some
attributes of the components involved. If they express much more than this, they
are usually considered to be a hardware description language such as Verilog or
VHDL, or one of several languages specifically designed for input to simulators or
hardware compilers (such as SPICE analog simulation netlists).

Types of netlists –

Netlists can be:

6. Physical (based upon physical connections) or logical (based upon logical

connections)
8. For example, connecting three components through one terminal of one of
those components would be considered a direct logical connection,
whereas each would be discrete physical connections.
7. Instance-based (clustered about a component instance) or net-based
(exhaustive list of connections to a particular net)
 9. Flat (all connections are shown) or hierarchical (connections are grouped in
some way; such as which physical board or layer they are connected to.
Such netlists may in addition be either folded, hiding data beneath a given
level of abstraction, or unfolded, being exhaustive and thus potentially
equivalent in content to flat netlists.)

Contents and Structures of a Netlist-

Most netlists either contain or refer to descriptions of the parts or devices used.
Each time a part is used in a netlist, this is called an "instance".

These descriptions will usually list the connections that are made to that kind of
device, and some basic properties of that device. These connection points are
called "terminals" or "pins", among several other names.

An "instance" could be anything from a MOSFET transistor or a bipolar junction

transistor, to a resistor, a capacitor, or an integrated circuit chip.

Instances have "terminals". In the case of a vacuum cleaner, these terminals

would be the three metal prongs in the plug. Each terminal has a name, and in
continuing the vacuum cleaner example, they might be "Neutral", "Live" and
"Ground". Usually, each instance will have a unique name, so that if you have two
instances of vacuum cleaners, one might be "vac1" and the other "vac2". Besides
their names, they might otherwise be identical.

Networks (nets) are the "wires" that connect things together in the circuit. There
may or may not be any special attributes associated with the nets in a design,
depending on the particular language the netlist is written in, and that language's
features.

Instance based netlists usually provide a list of the instances used in a design.
Along with each instance, either an ordered list of net names is provided, or a list
of pairs provided, of an instance port name, along with the net name to which
that port is connected. In this kind of description, the list of nets can be gathered
from the connection lists, and there is no place to associate particular attributes
with the nets themselves. SPICE is an example of instance-based netlists.
Net-based netlists usually describe all the instances and their attributes, then describe
each net, and say which port they are connected on each instance. This allows for
attributes to be associated with nets. EDIF is probably the most famousof the net-based
netlists.