Written By: Matt P. Lamparter - Amazon Web Services · Step 2 — Read Ultiboard tutorial from NI It is now time to familiarize yourself with Ultiboard. Begin by reading steps 5 and

PCB Design Part 2: UltiboardThis guide will show you how to layout components on a printed circuit board (PCB). Upon

completion you will have a set of Gerber files for fabrication.

Written By: Matt P. Lamparter

PCB Design Part 2: Ultiboard Release: Rivet Update [minor] 2019-02-07Guide ID: 32 -

This document was generated on 2019-09-29 04:56:01 PM (MST).

© 2019 bucknellmakers.dozuki.com/ Page 1 of 33

INTRODUCTION

This is part 2 of a 2-part series. The first part of this series requires the user to learn Multisim andcreate a firefly schematic. If you are not familiar with Multisim, please complete part 1 beforeattempting to use Ultiboard.

Published by Matt P. Lamparter with contributions from Ryder R. Nance.




https://bucknellmakers.dozuki.com/Guide/PCB+Design+Part+1:++Multisim/7

Step 1 — Continuing from Multisim

Now that your circuit is complete in Multisim it is time to lay out the physical components on aprinted circuit board.

We will begin by transferring all of the component and connection data from Multisim into Ultiboardvia something called a netlist.

You will be given a custom PCB shape with several components already placed for you. You willbe tasked with placing the remaining components and connecting them with traces on the PCB.

Step 2 — Read Ultiboard tutorial from NI

It is now time to familiarize yourself with Ultiboard. Begin by reading steps 5 and 6 in this NItutorial: Introduction to Multisim/Ultiboard.

Note that we have already provided power and ground connectors for you so you may ignore thisstep in the tutorial.




https://en.wikipedia.org/wiki/Netlist

http://www.ni.com/white-paper/10710/en/#toc5

Step 3 — Open the partial firefly PCB

Now download the partial PCBschematic file from the Maker-EGoogle drive.

Open the PCB file with Ultiboard.

You are already given the PCBshape and several components inposition: the IR emitters(LEDs)/detectors (phototransistor),the magnet, and the power supplypins.

Recall from the Multisim tutorial thediscussion of refdes values. Notethe refdes values shown in theexample here: U4, U5, U6, U8, U9,U10, etc. These correspond tocomponents in your Multisim file.




https://drive.google.com/open?id=1AwZlNurrz6956vaExEvNrjrYk0wo_XG1

Step 4 — Component and board requirements

If you plan on using the PCB mill in the Maker-E to fabricate your board, you should follow therules below to ensure the mill can successfully fabricate your PCB. Note that these issues arealready taken care of in the firefly example.

Avoid “leadless” packages such as QFN if at all possible.

Make sure your traces are 0.4 mm or larger. It is possible to go as low as 0.2 mm with the mill,but traces this narrow have a high probability of failing during the milling process.

Try to choose packages with a pin pitch of 0.5 mm or larger. Packages with a pitch of 0.5 mmmay require 0.2 mm traces.

If you will fabricate your board professionally (ie not in the Maker-E) your requirements are far lessstrict. But keep in mind that the smaller the component, the more difficult it will be to place on aPCB. Be sure to follow the design rules provided by the fabrication service you will use.




https://en.wikipedia.org/wiki/List_of_integrated_circuit_packaging_types#Dimension_reference

Step 5 — Forward annotate to Ultiboard

You are now ready to transfer your design from Multisim to Ultiboard. If you were creating a newPCB you would choose, from the Multisim menu bar, Transfer -> Transfer to Ultiboard ->Transfer to Ultiboard 14.0. This would create a default, rectangular PCB and you would need toresize the board to meet your specifications.

However, since we are providing you with a PCB file that already contains the correct dimensions,you will simply update this existing board with the changes you made in Multisim.

Perform this task by selecting Transfer -> Forward Annotate to Ultiboard -> Forward Annotateto Ultiboard 14.0.

When prompted, save the netlist file wherever you have your Multisim and Ultiboard files saved.

Confirm component updates in Ultiboard by clicking OK when prompted.




Step 6 — Confirm refdes

You now have all of the componentsyou need to complete the fireflyPCB. You will see the yellow“ratsnest” lines which indicate howcomponents need to be connected.Your task now is to place all of thecomponents within the bounds of thePCB and connect all of thecomponents using traces on the topand bottom of the PCB.

When you are done, there should beno ratsnest remaining. Instead, all ofthese yellow virtual connectionsshould be replaced with green andred traces.

If after forward annotating yourMultisim file into the existingUltiboard file you are missing any ofthe “orange boxed” componentsshown in this example, then there isan issue with your refdes values.Double check these values andmake any changes necessary inorder to make your Ultiboard PCBlayout look like the example shownhere.




https://drive.google.com/open?id=1An0p9xC57_dccvTExO0cDJ0-fxkm5C9R

The components surrounded byorange boxes have already beenplaced for you and are locked inplace. These cannot be moved asthey require precise placement inorder to ensure proper circuitoperation and communication withsurrounding circuits.

Step 7 — PCB Design Best Practices

There are a number of bestpractices you should keep in mindas you lay out your PCB. Thefollowing link will provide you with asummary of these best practices.

PCB Design Best Practices

Note that the process used torealize plated through-holes in theMaker-E requires a slightmodification to through-hole padsand drill holes. This will come intoplay when you begin through-holetraces on the top layer of your PCB.More on this later.




https://bucknellmakers.dozuki.com/Wiki/PCB_Design_Best_Practices

Step 8 — Configuring for design rules and fabrication requirements

You should begin by setting your design rules in Ultiboard by opening Options -> PCBProperties.

Look at the Grid & Units, Pads/Vias, and Design rules tabs. These are the areas where you canconfigure the design rules and various settings and parameters for your PCB.

For the firefly PCB you can use this technology settings file which has most of these settingspreconfigured. You will need to import this file into Ultiboard by choosing File -> Load technologysettings.




https://drive.google.com/open?id=1oc4xA9wBWn6sWumexwNvmgEfG1azczwG

Step 9 — Power planes - do you need them?

Examine your schematic in Multisim and determine if it would make sense to use one or two powerplanes in your PCB.

Power planes minimize the number of traces needed by providing a large copper area wherecomponents can be directly connected to a specific net. Often power and ground are good uses forpower planes, as many components require these connections. These planes can also provideprotection from unwanted radio frequency interference.

You can use one plane per layer in your PCB. If you have a two layer PCB (what we use in theMaker-E) you can use up to two separate power planes (ie you can associate two different nets:one with the top layer and one with the bottom layer). You can also keep the same net associatedwith both layers, use only one plane, or none at all!




https://en.wikipedia.org/wiki/Ground_plane#Printed_circuit_boards

Step 10 — Placing power planes

You can place a power plane by selecting Place -> Power plane from the menu bar. Ultiboard willthen ask you to choose a net and layer for the plane.

The example shown here would make the entire top layer of the PCB into a ground plane. Hence,any time a pad on the top plane needed to be connected to ground it would simply connect to thetop plane as opposed to creating a trace from this pad back to the common point where ground forthe circuit was connected.

Note that adding a power plane to a copper layer does not mean that every connection andtrace on that layer will connect to the power plane. Traces and pads that do not needconnection to the power plane will remain isolated from the copper plane.

See the examples shown here in the second image. Note the black isolation around the padlabelled +. This pad is not connected to the ground plane while the other pads are connected toground. The ground plane (right image) has rendered the previous trace (left image) redundantand thus it can be removed.




Step 11 — Issues with power planes and the mill

Adding a power plane may limit theamount of isolation you can havearound traces and pads if you planon milling your PCB in the Maker-Ewith the PCB mill. When you place apower plane in Ultiboard the defaultisolation width around everything is0.254 mm.

This value corresponds to the widthof the black isolation you see aroundall of the pads and traces inUltiboard.

If you plan to mill your PCB in theMaker-E, and you are using a powerplane, the mill will not allow you tocut isolation channels wider thanthis isolation value you define inUltiboard.

If you intend to increase the isolationwidth during milling (recommended,as this will decrease the possibilityof solder bridges) you will need toaccount for this isolation increase inUltiboard first before moving to themill.

If you cannot see your power plane,you may not have copper areasenabled. Select View -> Copperareas. This menu can also be usedto hide power planes from view ifthey are a distraction. This does notremove the planes from your design,just hides them for easier viewing.




Step 12 — Changing power plane isolation width

To change the isolation width, enable selecting copper areas and disable all other selectionoptions.

In the Design Toolbox double click the layer where the power plane is placed to activate thatlayer. The layer text in the Design Toolbox should be highlighted in red to indicate it is the activelayer. In this example we have activated the top layer.

Now right click on your PCB and choose Properties. Go to the General tab and change the Totrace value from the default 0.254 mm to whatever value you desire for isolation around yourpads.

Larger values translate to the possibility of more isolation when milling your PCB which can makesoldering easier due to the decreased possibility of solder bridging to residual copper.

If you plan on using the 1 mm end mill bit in the Maker-E PCB mill (which is recommended in thePCB mill tutorial), you will need to change the To trace clearance value to at least 1 mm to providethe mill enough room to use the 1 mm end mill.




Step 13 — The Copper Island Effect

Use caution when increasing this clearance value. As you increase this value what you are ineffect doing is removing more of your copper plane.

While this may make soldering easier, it can also cause connection issues by removing usablearea for signals to flow on the plane. This comes into play when you inadvertently create “copperislands” or portions of the copper plane that are cut off from the rest of the plane by traces andlarge swathes of isolation.

See the example shown here for an illustration of this copper island effect.

Power plane with default clearance of 0.254 mm, no issues.

Power plane with clearance of 0.55 mm. Notice that pins 4 and 8 are now isolated from the mainplane and thus require new traces for proper connection as evidenced by appearance of theyellow ratsnest. The pin 8 “island” is clearly visible while the pin 4 “island” is off screen.

Once you place power planes it can sometimes be difficult to see the other items on your PCB. Ifyou wish to disable viewing the power planes (while still leaving the planes as part of the PCB) youcan do so by choosing View -> Copper areas from the menu bar.




Step 14 — Potentiometer and test points

When you place your potentiometer(circular, adjustable resistor) andtest points, be sure to position themso that they are easily accessible tofingers and scope probes. Keepingthem close to the board edges is agood idea.

Now place your remainingcomponents. Pay attention to thePCB Design Best Practices to makeit as easy as possible to lay yourtraces.

Step 15 — Understanding trace width

You may wish to change the default trace width for certain nets, prior to laying traces. Forexample, perhaps you know that your power supply will be supplying high current to a particulardevice on your PCB. In this case you may want to increase the trace width for the power andground nets to accommodate this high current.

Note that trace width is dependent upon the current it will carry and the thickness of the copper onthe board. We use copper with a thickness of 1 oz/ft^2 in the Maker-E. You can find a PCB tracewidth calculator here. You will use the Results for External Layers in Air values. Pay attention tounits.





http://www.4pcb.com/trace-width-calculator.html

Step 16 — Modifying trace width

If you wish to change the trace width for entire nets, click on the Nets tab at the bottom of theUltiboard window. It may be convenient to drag the upper bound of this window vertically toenlarge the window.

Note that the units used for the net dimensions shown in the example here (0.4) are in millimeters.You can change the units for your board in the “Draw settings” toolbar.

As shown in this example, the default trace width for the firefly board is 0.4 mm which is sufficientfor this circuit. If you wish to increase the width for a particular net, you can do so by doubleclicking the Trace width box in the corresponding net row and entering the desired value.

Note that you can select multiple nets by using the Shift and Ctrl keys. This allows you to changethe width of multiples nets at once.

It is also possible to modify individual traces within a net by simply right clicking on them andchanging the properties.




Step 17 — Activating a layer to lay a trace

Once all of your components havebeen placed in such a way as tominimize ratsnest length and thenumber of ratsnest intersections,you are ready to begin laying traces.

Recall that every line in yourratsnest is a virtual connection:there is no physical connection yet,it is up to you to follow the ratsnest,determine where connections needto be made, and route traces fromthe beginning to the end of eachratsnest connection.

There are three methods of layingtraces, ranging from completelymanual to completely automatic. Wewill use the semi-automatic method.First, choose the layer where youwish to lay your trace (top or bottom)by double clicking it to make it activein the Design Toolbox.




Step 18 — Follow-me traces and vias

Now choose Place -> Follow-me from the toolbar. This method of placing traces will suggestpossible automated routes, but allows you some flexibility in customizing these routes. It is a nicetrade-off between automation and customization.

Follow-me will also prevent you from inadvertently making connections that are not part of yourschematic. Remember that any time two traces come in contact on a single layer, you have madean electrical connection. So if you need to run traces perpendicular to each other without touching,you will first need to switch layers using a via:

The example highlighted in green shows overlapping traces on the same layer. These tracesare connected.

The example highlighted in purple shows the use of vias to prevent traces from overlapping.The bottom layer is used in this case. These traces are not connected.




Step 19 — Place traces with follow-me

With Follow-me activated, singleclick where you would like your traceto begin. After you define abeginning point, Ultiboard willautomatically suggest a possibleroute for your trace to follow to itsdestination. You can modify thissuggested route by moving thecursor around the board.

If you wish to keep part of thesuggested route and change anotherpart, you can click on the PCB toanchor certain parts of the trace.When you click on the part of thePCB where the trace should end,the suggested route will become adefined route and your componentswill be connected.




Step 20 — Connecting traces and associating vias with nets

Go through and connect the rest of your components until all of the ratsnest is gone. You will mostlikely need to use vias as you switch between top and bottom layers. Try to lay out yourcomponents in such a way as to minimize the number of vias you need.

Note that after creating a via you should associate it with a net so that Follow-me will allow you tomake connections to it.

You can make net associations by right clicking on a via and choosing Properties. Within the Viatab, be sure to check the Assume net box and select the appropriate net.

You can view net names by zooming in on pads within Ultiboard to temporarily display a net name.




Step 21 — Vias and plated through holes

Vias and plated through holes (PTH) are common features of many PCBs. We have the ability toaccomplish both of these in the Maker-E.

However, be aware that the method we use to realize both of these is different than that employedduring professional PCB fabrication. Consequently, our design rules reflect this. The via designrules are listed in the PCB Design Best Practices document.

The method used to accomplish conductivity between copper layers is via small copper rivets,shown here in the second picture. These rivets require a hole of a particular size, plus anappropriately sized copper ring to accommodate the rivet flange. Failure to size vias/PTH properlywill cause problems with your board.

Depending on how you design your board, many of the through hole components that youuse will require vias (or plated through holes) in order to connect from the bottom to the topcopper layer. Before continuing, PLEASE read this page. It will help you to determine whereyou need vias.




https://en.wikipedia.org/wiki/Via_(electronics)

https://en.wikipedia.org/wiki/Through-hole_technology#History


https://bucknellmakers.dozuki.com/Wiki/Vias_and_PCB_Rivets#Section_When_do_I_need_a_rivet

Step 22 — SMT pad traces

Keep in mind that traces for surface mount components should begin on the layer on which thecomponent is mounted.

After beginning a trace on a SMT pad it is then possible to switch layers using a via.

A good example is shown highlighted in green. R5 is placed on the top layer, hence the pads areon the top layer, and the trace should begin on the top layer.

A bad example is shown highlighted in red. R5 is placed on the top layer, the pads are on the toplayer, but the trace begins on the bottom layer. There is no connection!

If you inadvertently mix up layers, Ultiboard may place a via on top of a SMT pad for you in orderto achieve connection. This is bad design practice for our process and should be avoided .




Step 23 — Resizing through holes for the Maker-E

Traces for through hole components can begin on either side due to the nature of the platedthrough holes. However, boards fabricated in the Maker-E require extra attention to platedthrough holes.

The process used in the Maker-E to realize through hole plating requires a hole size of 1.5 mmand a pad diameter of 2.5 mm.

If you have two adjacent pins with a standard spacing of 2.54 mm (0.1") you may reduce the paddiameter to 2.4 mm while maintaining a hole diameter of 1.5 mm. Ultiboard will generate a warningabout this spacing, but you can ignore this warning. This is applicable to several components usedin the firefly PCB.

Consequently, any time you wish to connect a trace to a through hole component lead on the toplayer, you will need to modify the hole for this lead by right clicking on the hole, selectingProperties, and making the size changes in the Pad tab.

The reason behind this modification is due to the soldering process. Through hole components aresoldered on the bottom of the board (when the component is placed on the top) so if a trace beginson the bottom there is electrical contact with the component lead when soldered on the bottom.

If a trace begins on the top layer, a board fabricated in the Maker-E will not initially provideconductivity from the bottom to the top because the hole is not plated with conductive material.The process required to achieve this conductivity necessitates enlarging the through hole size.




Step 24 — Take your time

Take your time. Don’t be afraid to move components around or remove traces in favor of differentroutes as you begin to make connections on your PCB. Laying out a PCB is a bit of an art and youwill become better with practice.

Again, refer to the PCB Design Best Practices for additional tips for beginners located at thebottom of the document.

Step 25 — Coffee break

When you have all of yourcomponents placed, all of yourtraces run, and all of the ratsnesthas been eliminated then you havecompleted your PCB design. Take abreak, get some coffee, and thendouble check your design.





Step 26 — Check that physical parts fit

Before proceeding on tomanufacture your board it is crucialto print out your entire PCB onpaper, place all of your componentson the PCB, and make sure that allof your footprints are correct.

A significant amount of money andtime can be saved when theseerrors are caught on paper asopposed to a PCB. If you find that apart does not fit on top of a footprintthe way you anticipated, you needto:

go back to Multisim and choosethe correct package, then forwardannotate to update Ultiboard or

adjust the footprint you created tocorrect the errors.




Step 27 — Printing your PCB on paper

To print your PCB, select File ->Print from the menu bar.

Be sure to follow these steps in theorder shown below:

Select the layers you want toappear on the printed page bymoving them from the left box tothe right box. You should printthese layers: board outline,silkscreen top, copper top

Select a zoom level of 100%

Uncheck the Print layers onseparate paper box

If you do not move layers into theright box first, you will not be able tochange the zoom options.




Step 28 — Printing power planes

If your PCB contains power planes, these planes will print out as solid black areas as part of the“copper top” layer. This is intentional.

However, if you find this distracting you can temporarily delete your power planes by:

disabling all selection tools and enabling only the Select copper areas tool ,

activating the layer you wish to remove by double clicking its layer name in the DesignToolbox,

enabling View -> Copper areas,

clicking on the copper area of your PCB to select it and then pressing Delete.

Deleting your power planes will cause several components to lose connection to the associatednet and thus many ratsnest connections will appear. You can ignore these. Just be sure to addthe plane(s) back when you are done printing!




Step 29 — What's a Gerber file?

Once you are sure that your PCB iscorrect, that all of your footprints arethe right size and you have all ofyour traces properly run, it is time toexport the PCB for fabrication.

Regardless of where your PCB willbe fabricated, the process is thesame. The industry standard filetype for PCB fabrication of the boardlayers is the Gerber file. There is aseparate file used for drilling theholes in your PCB called an NC drillfile which is typically in the Excellonformat.

Each layer in your PCB will export toa separate Gerber file. One file forthe top copper layer, one file for thebottom copper layer, one file for theboard outline, etc. There will also bea separate NC drill file.




Step 30 — Turning off fiducial marks

Prior to exporting Gerber files, it is necessary to turn off special markers known as FiducialMarkers. These markers will be discussed in more detail in the PCB Milling tutorial. For now weneed to disable them.

Open the PCB Design options window by clicking on Options -> Global options within the menubar.

Navigate to the PCB Design tab and uncheck the box next to Show global fiducial marks.

Click OK when you are finished.




https://bucknellmakers.dozuki.com/Guide/Fabricating+PCBs+Part+1:+Toolpath+Generation/4

Step 31 — Exporting Gerber files

To export your Gerber files, selectFile -> Export from the menu bar. Inthe left box of the window thatappears, be sure to check the boxesfor Gerber RS-274X and NC drill.

Pay attention to the following itemsin the properties portion of theexport window:

Check the box for Copper top

Check the box for Copperbottom

Check the box for Board Outline

All other layers should beunchecked.

Check the box for Metric outputunits if you will be using the PCBmill in the Maker-E. Otherwise,consult the recommendations ofthe board house you are using.




Step 32 — Configuring the NC drill file

After configuring the options for theGerber files, click on the NC drilloption in the Exports box and makesure that the output units matchthose chosen for the Gerber files.For the PCB mill in the Maker-E thiswill be Metric.




Step 33 — Confirm file export

After configuring all of the options,click Export.

By default your Gerber files will beexported to a newly created foldercalled Ultiboard Exports as asubdirectory within the folder whereyour Ultiboard project file is saved.Navigate to this folder and confirmthat you have the following five files:

yourProjectName - BoardOutline.gbr

yourProjectName - CopperBottom.gbr

yourProjectName - CopperTop.gbr

yourProjectName - Copper Top-Copper Bottom.drl

yourProjectName - Drill Info.rep




Step 34 — Congratulations!

Congratulations! You just designed your first PCB. If you feel your design is complete, pleasecontact the Lab Director for review before proceeding on to the PCB mill tutorial.

Be sure to email your Ulitboard project file (*.ewprj) to the Lab Director for review.




https://bucknellmakers.dozuki.com/c/PCB_Mill

Documents

Written By: Matt P. Lamparter - Amazon Web Services · Step 2 — Read Ultiboard tutorial from NI It is now time to familiarize yourself with Ultiboard. Begin by reading steps 5 and