PCB layout

1 Screenshot

The main elements of the window:

1.1 Menu bar containing the menus File, Edit, View, Project, Tools, Add and Help

1.2 Taskbar (just below the menu bar), illustrated with 8 buttons and 5 pull-down menus to set the units of measurement Units (mil or mm) intervals grid visibility Visible, the Placement and routing Routing, and bend angle Angle (in degrees).

1.3 List of the layers on the left side of the client area, with windows next to each layer, showing the color and visibility.

1.4 The choice of mask layers below the list, with fields to allow / disallow selection of different items.

1.5 The window placement, which shows the PCB.

1.6 Menu function keys below the list of layers and layout window, showing the available commands function keys.

1.7 The status bar at the bottom of the window.

2 Menu

The menu bar provides the following menu:

♦ File

• New — create a new project PCB (shortcut key = Ctrl-N)

• Open … — open the project file, PCB (shortcut key = Ctrl-O)

• Save — save the project file, PCB (shortcut key = Ctrl-S)

• Save As … — save PCB design file under a new name

• Close — close the project

• Import netlist … — import the netlist file

• Export netlist … — export a netlist file

• Convert library … — convert a library of footprints format Ivex format FreePCB

• Generate CAM files … — to generate gerber files, and Drill

• Open Footprint Editor … — move from the PCB Editor footprints editor

• Export .dsn file … — Export file design autorouter

• Import .ses file … — import the file session of autorouter

• Print … — (not yet implemented)

• Print Preview — (not yet implemented)

• Print Setup … — (not yet implemented)

• Exit — close the application

♦ Edit

• Undo — undo the last (shortcut key = Ctrl-Z)

• Cut — to save the clipboard and delete (only available for groups)

• Copy — to save the clipboard (only available for groups)

• Paste — paste from the clipboard (only available for groups)

• Save group to file … — save a group as the project file

• Paste group from file … — to insert a Project file as a group

♦ View

• Show board outline — change the scale to display the entire board

• Show all — zoom in to see all the elements of accommodation (abbreviated = Home)

• Show part … — open a dialog to select the component

• Layers … — open a dialog view / edit layers

• Show log … — Show Log Window

♦ Project

• Options — open a dialog for editing the Project Options

• Parts … — open a dialog View / Edit to edit the list of housing buildings

• Nets … — open a dialog View / Edit to edit the connection netlist

♦ Tools

• Move origin — Origine move the coordinate system to the new position

• Footprint Wizard — Wizard open the footprint to create a new footprint

• Footprint Editor — open the footprint editor to create or edit footprint

• Check parts and nets — Check the project for the internal database error

• Check traces — check and clean the track

• Check connectivity — check out the project to connect the incomplete netlist

• Check Copper Areas — check polygyny, if you want to merge

• Design Rule Check — Check the consistency of the rules of the project and show an error

• Clear DRC Errors — Clear symbols for all DRC errors

• FreeRoute autorouter … — start the on-line autorouter FreeRoute

♦ Add

• Board Outline — add a circuit board

• Part — add new case

• Net — (not yet implemented)

• Copper Area — to add landfill

• Text — add a line of text

• Solder Mask Cutout — add a circuit in the layer of solder mask

3 Taskbar

It has 8 illuminated buttons, which are shortcuts to the following menu items:

□ Open

□ Save

□ Cut

□ Copy

□ Paste

□ Print

□ About

They are accompanied by 5 pull-down menus to set the unit and the grid used in FreePCB.


□ Units — select mils or mm to measure the size

□ Visible — set the length of a rectangular array of points in the layout window, as visible links

□ Placement — set the grid for placing buildings, text, etc.

□ Routing — to set the grid for routing paths and drawing polygons

□ Angle — set the angle of bend (in degrees) for routing paths, drawing boundaries boards and polygons

The default data for the drop-down menus (except the menu Angle) in the file default.cfg, in the folder that contains FreePCB.exe. When the project is created, they are copied to the options section of the project file. They can be modified with any text editor, such as such as Notepad.

4 Status Bar

It contains the following elements:

■ Hint ("Ready"), Which changes, if the cursor is placed over the various user interface elements

■ X and Y coordinates of the cursor in mm or mils

■ Information about the element that is selected (if selected). In the example above, the body U1 has been selected. His reference designator, footprint, position, angle and side displayed.

■ Current traced layer ("Top")

5 The list of layers and selection mask

These are two vertical list in the FreePCB, to the left of the field placement.

5.1 Layer List

This — a list of all layers of paint used in the project. Next to the name of each layer of a small square showing the color of the layer. If the level has been made invisible, the square will be white with "X" therethrough (such as "inner 1" and "inner 2" in the example). You can toggle each layer from the visible to the invisible, by clicking on the square. The layer of active tracing ("top copper" in the example below) is identified by an arrow — pointer. You can change the active trace level by pressing a numeric key on the keyboard (ie keys "1" before "8"), Or by clicking on the layer name in the list. The active layer routing will always be displayed on top of other layers in the layout window.

5.2 Mask selection

Elements in the placement, you can choose to edit by clicking on it or by drawing a rectangle around them with the mouse. Since the elements can overlap each other, it is sometimes difficult to select exactly the element that you need. In this case it is possible to use a selection mask to enable or disable selection of the various element types. The mask consists of a list of types with colored blocks next to each. Green block means that the type of item can be selected, while the red box means that this item can not be selected. You can switch the status of each unit by clicking on it.

6 function keys and context menu

Most programs drawing procedure of Windows use "click-drag" mouse editing. That means holding down the left mouse button while moving it. You can, for example, change the size of the element by clicking on it, which entails the appearance of a block selection "grippers"Which can then click and drag to increase or decrease the element. The endpoints of the line can be dragged to a new position of the click, etc., etc.

7 Panning and zooming

Keep in mind that in the FreePCB no scroll bars. Use the scroll bar to pan is not very practical for program placement PCB, as the forces often operate pan, directing track or moving body. This is inefficient as forces move the cursor from the workspace to the scroll bar.

Therefore, pan and zoom into FreePCB performed or the keyboard or (preferably) by scrolling the mouse. To pan, move the cursor to the point on the PCB, which will be the new center of the image, and press the space bar or mouse wheel to scroll through one detent in either direction. Image re-centered on the cursor position. To zoom in, press "Page Up" or scroll mouse wheel forward more than one detent. To zoom out, press "Page Down" or mouse wheel to scroll back. If you have a wheel mouse, I would recommend to buy it.

You can display the entire circuit PCB, using View-gt; Show board outline menu item. You can show all of the elements in the project (which can be located outside the PCB), selecting View-gt; Show all, or by pressing "Home". You can select the housing and pan to its location, using the View-gt; Show part …

8 Projects

In FreePCB, printed circuit boards are referred to as projects. All information describing the project are stored in a single text file with the extension .fpc, which is usually stored in a folder with the same name as the project. For example, a project called "Motor" It will be saved in a file Motor.fpc, located in the folder C: FreePCB projects Motor

9 Elements of PCB

9.1 The individual elements

Introduction of PCB in the layout window is composed of various elements that are listed in this section.

Note that most of them can be selected by clicking on them. Once the item has been selected, it can be to perform the operation, by pressing the function key or clicking the right mouse button and choosing from the context menu. If the operation involves the moving element, the function keys can sometimes be used to perform additional operations, while the movement takes place.

9.2 Groups elements

Groups of elements can be selected by drawing a rectangle around them with the mouse. All the elements in the group are highlighted. Individual elements can be added to a group or removed from it by clicking on them with the key held down CTRL. Operations that can be performed on groups:

■ F4 (Move Group) — starts moving group

■ F8 (Delete Group) — deletes a group from the project

■ ctrl-C — copy the group to the clipboard

■ ctrl-X — a group of copies to the clipboard and removes it from the project

9.3 Moving elements or groups of cursor keys

When an item or a group of selected, you can move them with the mouse, selecting the move operation function keys or the context menu. Most of the elements and groups can also be moved by pressing the cursor keys on the keyboard. Pressing the arrow keys will move the element or group by a distance equal to the current placement step or trace, depending on the selected item. Smaller movements can be made by holding the SHIFT key and pressing the arrow keys that move the item to 1 mil or 0.01 MMS, depending on the modules used.

10 Circuit board (Board Outline)

The circuit board is the border PCB. In FreePCB circuit consists of a closed polyline (closed polyline) (polygon or polygon) consisting of three or more parties, with the angles between the sides. The parties may be straight line segments or arcs arcs. Arc — one quadrant of an ellipse whose major axis is parallel or x or y. The advantage of using this determination limited arc is an arc that is fully defined position of its endpoints and the direction, which can be either clockwise or counterclockwise. Card Type species consisting of the 10 angles and sides 10, is shown below. Note that two of the sides — of the arc.

The project may be more than one circuit board.

11 Cases

11.1 Anatomy buildings

Each PCB includes one or more housings. Each body comprises the following elements:

• Reference designator (reference designator), such as "U1" — Which is usually assigned to the scheme and should be unique.

• Package identifier (ID of the package), such as "DIP14" — The body have different physical packaging and PCB designer should know which packaging will be used for each body because it will determine the housing footprint footprint in PCB.

• Pins (conclusions) — electrical terminals of the housing. Conclusions identified name (usually a number) that is appended to the reference numeral, such as "U1.4" for the fourth output body U1. The path name will depend on the findings of the body. All terminals must have a unique name, even if they are interchangeable like a resistor, for example.

• Mounting holes — Mounting holes can be used for fixing the housing to the PCB. Fixing such as screw holes, or may require the body may have built-in mounting such as PressFIT (pressed landing) or solder terminals. Mounting holes may be insulated or may have a bonding pad and be plated. Often used mounting holes plated, which allows to connect the electrical circuit, such as earthing the screen of the connector to the housing. Therefore, FreePCB handles all the fixing holes as the conclusions. For the names of the mounting pins are commonly used numbers that are higher than the numbers used for conventional terminals. For example, a 9-pin D-SUB connector with 2 mounting holes would mounting output at number 10 and 11.

• Footprint — This is a pattern of copper pads and other items that will become part of the PCB placement.

11.2 List of enclosures (Partlist)

In FreePCB, all buildings in the project are contained in a data structure called the partlist, which is empty when the project begins to be created. Normally, the body added to the partlist in import netlist (netlist file) from the schema editor. This will be discussed in Section 5.14: Importing Netlist Files. You can view or edit the partlist, paragraph selecting Parts … from the menu Project, which brings up a dialog View / Edit Part List.

11.3 Editing enclosures (Editing Parts)

Shells can be added, deleted or modified by means of dialogue View / Edit Part List.

11.4 Moving or resizing tag

11.5 Creating an invisible tag

If you set the character height to position the text "0", Reference designator will become invisible. To make it visible again, click the body and click the right mouse button and select Set Ref. Text Size from the context menu that appears. Then set the character height of a non-zero value.

Positional notation for the body can be moved by selecting it and pressing the F4 ("Move Ref Tex").

12 Mounting holes

The mounting holes are used to attach the PCB to an external structure such as a bracket or body. In FreePCB, mounting hole has a housing which consists of a single discharge hole. Padstack for O legs may include sites that can be used to connect the mounting hole to the mix, just like any other pins. The actual hole in the padstack will be shown in color for the porting layer. If the mounting hole has a site, they will be shown in color for their copper layer.

13 compounds, Ratlines and Wiring

13.1 Links

Compound sets legs which are connected together on the PCB. Each must have a unique name. This name can be descriptive (such as "GND" or "video_in") Or a distinctive (such as "N06744"). The title compound FreePCB limited length 40-characters, and may contain special characters. Each output is identified in connection string of the tag body, containing the output symbol "." and the name of the output.

13.2 The list of connections

In FreePCB, all information about the connections is stored in a data structure called a netlist. This list can be viewed and changed by selecting from the menu Nets Project. This causes a dialog box View / Edit Netlist.

This dialog contains a list of all links in the project. For each link shows the name of the Name, the number of connected terminals Pins, the default track width Width, Width Via W and the diameter of holes Hole transitions.

The switch next to each name determines the visibility of the connection. If the block visibility is not selected, ratlines for this compound will not be displayed in the layout window. This is useful when you are working with a particular compound and do not want to be distracted by other ratlines. Button Make all visible / invisible allows you to simultaneously turn on / off the visibility of all connections.

13.3 Ratlines

Typically, the circuit can be connected sequence of lines, where each line connects two conclusions. For any compound containing more than 2 output will be several ways in which these conclusions can be connected.

13.4 Change Ratlines

Most of the time, you will use ratlines, which calculates FreePCB. However, there may be situations where you want to have more control over ratlines. FreePCB provides several options for editing ratlines:

• ratline can be blocked by selecting it and pressing the F3 ("Lock Connect"). Appearance ratline will not change, but "L" in her description in the status bar will indicate that the connection is blocked. Locked connection is removed when FreePCB recalculates ratlines. Locked connection can be unlocked by selecting it and pressing the F3 ("Unlock Connect").

• The connection can be added to the mix by selecting the starting platform for output connection, and pressing F4 ("Connect Pin"). Then you can stretch ratline to a different conclusion on the same circuit.

It is usually necessary to block ratline after adding, otherwise this connection, most likely, will be deleted the next time the program after recalculating ratlines. In the same way one can make a connection to the unassigned pin when a new output is added to the circuit.

• ratline can be removed from the chain by selecting it and pressing F7 ("Delete Connect"). If ratline blocked, you will be prompted to unlock it. If you delete ratline and do not replace it, adding and blocking the other, then the most likely appear again the next time the ratlines be recalculated.

• ratlines for each connection is usually re-evaluated after each editing operation, which affects the connection. Exceptions are those operations which directly change ratlines, such as those described above. To force FreePCB restore ratlines, press F8 ("Recalc. Ratlines").

13.5 Routing with Ratlines

This method consists of converting ratlines in copper traces. The tracks consist of one or more straight line segments that are connected together with a break in their connection points. If the two adjacent segment are on different layers, then the transition will be placed in a break between them.

13.6 Removal

13.7 Wiring chopped off tracks (Stub Traces)

In addition to the tracks connecting the component pins, FreePCB supports stub traces. This is a track that starts on the withdrawal of a single component, but does not end with the withdrawal of the other. Instead, they simply break off or terminate the transitional hole (Via). Stub traces are used primarily to connect to the SMT terminals copper polygons, which are described in Section 5.15: Polygons. To create a stub trace, select the starting output and press the F3 ("Start Stub") To start drawing a track segment. The segment will be formed in this active layer, if the output terminal being SMT, is not located in another layer. In the latter case, the active layer is automatically changed to the output layer SMT. With left-click will place a kink track. If more than one segment, add additional fracture. Stub trace is completed by clicking the right mouse button. The track is over and it will be automatically added to the end of the transition hole. If you do not need a via, then select it and press F3 ("Delete Via"). If the transition is connected to the copper polygon on the same side of the board, where the output start to be formed thermal barrier compound pad vias and copper area. Example stub trace, component output is connected to the copper polygon is shown below. Thermal barrier represented by the symbol "X"Located on top of the transition hole and having a color ratline.

13.8 The layout of the track branches (Branching Trace)

Once a track is created, you can add it to the branch, which will connect the existing track with the other ends of the same chain.

13.9 Transitions (Vias)

Vias or simply transitions are used to connect the copper elements on different layers. In FreePCB, they are considered part of the track, and can only appear in the fracture path. Transitions can be compelled or forced unconstrained unforcsd. Unforced transition is automatically generated during the layout of the track. This will happen whenever it will be necessary to connect the track segments on different layers. If a track change, so that the need no longer in transit, then the transition will be automatically deleted. Usually, it is this behavior is more natural. However, there are times when I would like to leave a via between adjacent segments of the tracks that are on the same layer. For example, you would like to help the transition path to connect to a copper polygon. In this case, it is possible " cause" transition by selecting the break and pressing "f". Forced transition will not be deleted automatically. The type of transition can be determined by selecting it and looking at the status bar, which will show ("F") Forced to move. Forced transition can be made unforced pressing "u". Keep in mind that the transitions are created automatically at the end chopped off the tracks, forced by default.

13.10 Changing tracks

You can change the track by its segments, or breaks ratlines and using the command function keys. You can select the entire track by clicking on its segment or fracture and hold down "t". You can select the entire chain by clicking on a segment fracture or component output and hold down "n".

13.11 Change of findings (Swapping Pins)

You can change the findings in one case by one of them, holding down "s"And clicking on a different conclusion. Then pop up a window in which you will need to confirm the exchange or refuse it.

14 Importing Netlist Files

14.1 netlist file

After creating a new project, you must add the body and connected by importing a netlist file. This file is usually generated by the schematic editor, but, if necessary, can be created manually.

14.2 Import netlist file in the project

We import the netlist file by choosing File gt; Import netlist ….

14.3 Export Netlist Files

You can export the netlist file of the project using the menu item File gt; Export netlist …. so the Create a file for each component to be mapped footprint used in the project.

15 Landfills (Copper Areas)

For connections on the circuit board, in addition to the tracks can be used polygons (large areas of copper).

They are commonly used for distributing power supply and ground, if they can take the whole layer of the board. In FreePCB, all landfills must be assigned to the appropriate circuit.

The contour polygon is drawn closed broken line, just as drawn border of the board. The landfill can see a simple contour line, contour line with internal shading or contour line with a small hatch along its inner edge. These hatching patterns are used only for imaging, since the actual on-board test site will be made of solid copper. FreePCB automatically create gaps around any pads or tracks that pass through the copper area in the same layer. However, these gaps are not displayed, but the files will be created in Gerber.

To create a new polygon, select Copper Area menu Add.

Cuts in the range 15.1

Sometimes it is useful " Cut (cut out)" part of the landfill. This may be done in order to create an open area in the range, or to change its contour. To create a cut-out, select the side or corner of the polygon and press F6 (Add Cutout). Then draw a cutout as well as to drawing a new polygon.

Text 16

Text strings can be added to the layer serigraphy or copper layers PCB. They are useful to show the kind of information, such as the different notes, the version number, copyright notice, etc.

Add a text string to the PCB, by choosing Text from the menu Add.

17 Cuts in the solder mask (Solder Mask Cutouts)

Solder mask Solder mask is a coating that is applied to the printed circuit board to prevent sticking is not necessary to solder. It is not really necessary for the boards soldered by hand, but is essential for boards that solder automatically using solder bath or backward-wave technology. In the CAM process assumes that the solder mask is "layer" PCB, and described in Gerber-file, as well as the copper layer or layers of screen printing. Usually there are upper and lower solder mask, with separate Gerber-files for each.

The solder mask should be made cutouts for the sites, since they require solder. FreePCB creates these cuts automatically Gerber-files for solder mask layers, using a gap defined in the CAM dialog. Sometimes it may be necessary to create additional cuts in the solder mask. For example, edge connectors board should be open around them to prevent "Jumper" solder mask between the pads connector. Or, you might want to have a blank copper area for shielding or cooling. In FreePCB, these findings are referred to as cut-outs cutouts. You can add a notch in a layer of solder mask using Add gt; Solder Mask Cutout.

18 Groups

In addition to manipulating the individual elements of the PCB, you can also perform operations on groups of groups of elements. Group may contain any elements PCB. To select a group of items, click the left mouse button and hold the left mouse button, move it so that the selection rectangle to cover them.

19 Checking design rules (Design Rule Checking)

In an ideal world, the circuit board is always produced exactly as specified in the Gerber-files and drill. In real life, of course, it is not. Due to the inaccuracy of the etching process, the copper area may be slightly larger or smaller than specified. The layers of the multilayer board, is not likely to vystroyutsya exactly in line and the size and position of the holes may vary due to manufacturing tolerances. In practical terms, this means that there is a minimum track width requirements, the size of the gaps between the platforms and tracks and / or holes. These requirements called design rules Design Rules and varies depending on the production process.

20 Export of Gerber files and drilling

20.1 Creating Files

The final step is to export PCB design files, manufactured by the firm will use to make your payment. These files are described below.

• Gerber files — These files are used to create a photomask to be used to make copper layers and layers of silk-screen printing masks for PCB. There is one file for each layer or mask. Used extended format Gerber RS274X.

• Drill File — This file will be used by a machine that drills holes in the PCB. It uses a format Excellon, which is the industry standard. Basically, it starts with a list of drill sizes (in inches), and then gives the coordinates of the center of each hole. There is an important issue with respect to the size of drill, which is discussed in Section 5.19.3 Dimensions drills. Please read this section before you send your files to the manufacturer’s PCB.

To export files Drill and Gerber-files, select Generate CAM files … from the menu File.

In the section Files, select the files you want to generate, checking or without checking the boxes next to each. Gerber file options section allows you to select or deselect the following options:

• Include board outline — select this option to include circuit boards in all Gerber-ah.

• Add moires — add moire symbols (sometimes called "objectives") For recording layer.

• Add layer description text — add text string in each Gerber file indicating layer it represents.

• Add pilot holes to pads and vias — adds the pilot hole to the pads with a hole and goes to the top and bottom layers to aid in drilling.

• Use thermal reliefs for pins — when connecting pads with holes to the inner copper layers, use a thermal barrier.

• Use thermal reliefs for vias — chopped off when connecting tracks to the inner copper layers with transitions, use a thermal barrier.

• Make cutouts in solder masks for vias — to create the opening in the solder mask around the transition areas.

Gerber file dimensions section allows you to set values ​​for the following:

• Copper to copper-fill clearance — a gap that will FreePCB around tracks or passages that pass through the copper polygons.

• Hole-edge to copper-fill clearance — a gap that will be created around the drilled holes. Please refer to Section 5.194: Drill Clearances for important notes about these gaps.

• Solder mask clearance — a space that will provide FreePCB around the grounds in the solder mask.

• Pilot hole diameter — the diameter of the pilot holes, if you choose them.

• Minimum silkscreen stroke width — the minimum stroke width, which will be used to FreePCB silk layer, which is generally recommended by the manufacturer of the board.

• Thermal relief line width — the width of the lines that will be used to connect the pads or transitions to a polygon using a thermal barrier.

• Board outline line width — the width of the contour line of the board, if used.

• Annular ring width (pins) and Annular ring width (vias) — width of the copper ring placed in the inner layers around the pins and vias connected thermal barrier to copper polygons.

Section Panelizing allows you multiply your design, creating multiple copies of files PCB Gerber: Number of boards (x) / (y) — the number of copies in each axis. Spacing edge-edge (x) / (y) — a gap between the edges of the copies in each axis.

When you click Create Files, files are written to the Output folder. By default, this is — a subfolder CAM, located in the project folder. It will be created if nonexistent. You can change the output folder, or to reset the folder to the default, by pressing the Set default. If done correctly, you buvidite following Log dialog, with the final string SUCCESS. If in the process of generating a file errors occur in the log file will be relevant messages. If an error occurs during the generation of the file, FreePCB interrupts generation of the file and proceeds to the next. Each file is named according to its content, such as top_copper.grb or drill_file.drl.

When you have finished creating the file, press Exit dialog Generate Gerber and Drill Files.

20.2 Viewing and Printing Files

There are many free programs that allow you to view the Gerber-files and porting. Before sending your files to the manufacturer, I strongly suggest you check them one of these programs. I’m using the ViewMate from PentaLogix (before Lavenir). You can download this viewer at www.pentalogix.com/Download/download.html. ViewMate lets you view and Gerber files and files porting and allows you to make a test print to the printer. Since printing functions into FreePCB not yet implemented, it is now — the only way to print your projects.

20.3 Dimensions drills

Drill file determines the size and position of each hole in the PCB. The problem that arises with these files, the conversion to the actual size of the hole drill size (when the final hole diameter is less than a few mils after plating), or the size of the final (or plated size), which is the final size of the hole after plating. I have made more sense to determine the final size of the board and allows the manufacturer to choose which drill to use, as they know best how thick they will metallization layer. FreePCB footprint using finite dimensions, so these are the sizes that appear in the file porting.

You should specify the size of your manufacturer, since some of them expect the actual diameter of the drill, which must be greater than the final size of the hole. In this case, you may have to edit the file and increase the size of porting practical working respectively. Your motherboard manufacturer should be able to help with this if they understand what you want.

20.4 Clearances drilling (Drill Clearances)

Manufacturers will often recommend boards "drill clearance". This — the minimum recommended size of the gap around the opening in the inner layer of copper, which is created around the holes and allows safe passage hole through the inner layers without faults. As a rule, it is defined as something like "drill diameter plus 0.025 inches". It refers to the diameter of the clearance hole. FreePCB uses Hole-edge to copper-fill clearance meaning to create these gaps. However, since this clearance FreePCB processes as the distance between the edge of the hole and the edge of the copper is the aperture radius is the difference, which is half the difference in diameters. Therefore, to create a clearance hole " drill diameter plus 0.025 inches"You must use the Hole-edge to copper- fill clearance of one half of 0.025 inches, or 12.5 mils. This is rounded up to 13 mils.

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