Manual Footprint Creation in Altium 365
The next step in creating the component is to design the footprint. Component footprints contain a set of graphical primitives and copper pads or holes that will be connected to the conductors and will provide a connection. Also, the component itself will be soldered onto these contact points, so their configuration should be fully consistent with the actual metal objects of the component. Any error in the placement of the footprint pads can lead to problems, up to and including the inability to assemble the final device, so library designers should be very careful while creating footprints. In Altium Designer, the process of creating footprints is simple, convenient and protected from errors as much as possible. Let’s create a footprint for the GSB343K33HR component whose symbol was created in chapter 5.1. If you have closed the tab with this component, search for it in the Components panel, right-click on its name then select Edit. This connector cannot be created automatically using the IPC Compliant Footprint Wizard, so it must be created manually using the recommended PCB layout view from the datasheet.
Click the arrow to the right of the Wizard button below Add Footprint then select New to create a blank new footprint.
Tip: If you are creating an IPC compliant component, you can click the Wizard button for a quick way to create a footprint with all the necessary graphics, and to generate a 3D model for it. Using the IPC Compliant Footprint Wizard is described in Chapter 5.4.
We will create a footprint for this component referencing the recommended PCB layout that is present in the component datasheet. In this drawing, you can see all the dimensions of the metal pads, holes, cutouts, and the gaps between them, which are sufficient to create a footprint that will correspond to the real part case specifics.
In the Other region of the Properties panel (in Library Options mode), change the Units to mm.
According to the drawing, the pins are 1.35x0.4mm and their numbering is arranged in order starting from the left. Select Place > Pad from the main menus. Press the Tab key then define the following values in the Properties panel:
Layer: Top Layer
After the values have been defined, place the pad to the right and above the origin of the coordinates. The exact coordinates for all pads will be specified later.
After you have placed the first pad, the same pad is attached to the cursor and ready for placement with an increased Designator value of 2 by using the automatic numbering of the pads. Place nine more pads to bring the total in the working area to 10 pads.
We now need to place two slot holes on the left and right side of the component. Select Place > Pad from the main menus. Press the Tab key to define the following values in the Properties panel:
(X/Y): 1.5mm / 2.3mm
Hole Shape: Slot
Hole Size: 1.3mm
After all values have been specified, place one pad on the left and one pad on the right as shown in Figure 6.
We now need to adjust the coordinates of all pads so that they correspond to the requirements of the drawing. The drawing with the recommended PCB layout shows that the dimensional anchorages are made from the slot holes, and the distance between these holes is 12.55 mm. However, they are offset relative to the center.
Select pad 11. Enter -6.7/2-3.6 into the X coordinate field and 0 into the Y coordinate field. The pad will move to the desired coordinates after the coordinates have been updated.
Select pad 12. Enter -6.95+12.55 into the X coordinate field and 0 into the Y coordinate field.
Now let’s finish the SMD pads placement. They must be placed above the center and should have the same Y coordinate, so first, we will calculate the Y coordinate. Select all SMD pads and define their Y coordinate as 3.35-(1.35/2). Divide that by 2 because the size binding goes to the upper edge of the contact area.
The next step is to set the correct X coordinate distance between the SMD pads. The drawing shows a 6.7 mm distance between the centers of pad 3 and pad 8. Therefore, pad 3 will be placed at -(6.7/2)=-3.35mm for the X coordinate and pad 8 at 3.35mm for the X coordinate because they are symmetrical. Let's calculate the coordinated for pad 1. The pitch between SMD pads in one group is equal to 0.65mm (2.6mm/4). Consequently, the edge pads will have an X coordinate equal to (3.35mm +0.65mm +0.65mm)=±4.65mm.
Define the X coordinate for pad 1 as -4.65mm.
Define the X coordinate for pad 2 as -4mm.
Define the X coordinate for pad 3 as -3.35mm.
Define the X coordinate for pad 4 as -2.7mm.
Define the X coordinate for pad 5 as -2.05mm.
In Altium Designer, it is possible to automatically place selected pads evenly, but for this design, it is necessary to know the coordinates of the edge pads. Select pad 6. Since it should be placed symmetrically with pad 5, it has the same X coordinate, except with the opposite sign. Set the X coordinate for pad 6 as 2.05mm.
Select pad 10 and define its X coordinate as 4.65mm.
In order to perform this step correctly, all the remaining pads must be placed between pad 6 and pad 10! Select the right half of the pads, right-click on one of the selected pads then select Align > Distribute Horizontally. Now all pads of this group are evenly distributed between pads 6 and 10 and have the Pitch set to 0.65mm.
The main part of the component is ready. Now we need to add the graphics, which will be imported to the Assembly, Overlay, Courtyard, Designator, and Component Center layers. The graphics layer for the Assembly layer should include all component boundaries, including information on the first output. These graphics should be also created in reference to the component drawing in the datasheet.
Open the View Configuration panel. Right-click on any layer in the Layers region then select Add Component Layer Pair. Select Assembly from the Layer Type drop-down menu. Click OK to add a new layer pair.
Make the Top Assembly layer active. This layer is required to place a drawing that is necessary when designing the assembly drawing.
On this layer, we need to place a primitive set with the overall dimensions of the component and mark the first pad. Select Place > Line from the main menus. Draw a straight line below the central axis. After the line is placed, select it to define the following parameters in the Properties panel:
Start (X/Y): -7.1mm/-2.45mm
End (X/Y): 5.9mm/-2.45mm
The placed line should look like the figure below.
Add one more line to the Top Assembly layer with the following parameters:
Start (X/Y): -7.1mm/-2.45mm
End (X/Y): -7.1mm/3.65mm
The placed line should look like the figure below.
Copy and paste the placed lines one by one to finish the rectangle.
The next step is to add the indicator of the first pin. As a rule, it is indicated by a small circle placed inside the component contour. Select Place > Full Circle from the main menus and draw a small circle near the first pin of the component.
After adding the graphics for the assembly drawing, we need to add a graphic on the overlay layer (silkscreen). Graphics from this layer are used to simplify installation and subsequent repair of the device, and will also be drawn directly on the board. In most cases (except for BGA components), the silkscreen corresponds to the contour of the component but has a gap from all copper contact pads to avoid silkscreen ink getting on copper pads. You can find the recommended gap size for the silkscreen from your PCB manufacturer. In the case of the GSB343K33HR component, the gap between the top pins and the component contour is 0.25mm, so overlay lines can be drawn similar to the assembly drawing graphics added in the previous steps.
Make the Top Overlay layer active. Enable dimming in single layer mode by pressing Shift+S. Select Place > Line from the main menus. Press the Tab key then define the Line Width as 0.15mm in the Properties panel. Repeat lines for the contour of the component that is drawn on the Top Assembly layer. Do not forget that the copper plate of the slot holes (Pins 11 and 12) should also have a gap between the metal and silkscreen lines. Draw the first pin mark outside the component contour using Place > Full Circle. The final result of this step is shown in the figure below.
Tip: You can measure the distance between objects by pressing Ctrl+M.
Tip: It is better to draw right-angled lines with the Line 90 drawing style. The drawing style (shown in the Heads Up display) can be switched using Shift+Space while in line placement mode.
The next step is to create a Courtyard layer, which is necessary to implement component creation to a certain level of board placement density. This layer is represented by a rectangle with some gap either from the edge pins or from the component edge, whichever is larger. According to IPC-7531, there are three levels of mounting density:
- Level A (low mounting density, gap between pins/component edge = 0.5 mm)
- Level B (medium mounting density, gap = 0.25 mm)
- Level C (high mounting density, gap = 0.1 mm).
For example, we are designing our boards with Level B density, so we select a 0.25mm gap.
Open the View Configuration panel. Right-click on any layer in the Layers region then select Add Component Layer Pair. Select Courtyard from the Layer Type drop-down menu. Click OK to add a new layer pair.
In order to realize the medium density of component placement, a rectangle with a gap of 0.25mm must be drawn from the edge pins and/or the edge of the component. With the current component, the gap must be provided from both the component contour (top and bottom edges) and the slot holes to the sides (as they are outside the component contour).
Make the Top Courtyard layer active. Using Place > Line, draw a rectangle with 0.15mm Line Width as shown in the figure below. You can check the resulting gap with the measuring tool by clicking Ctrl+M. Measuring should be performed between the centers of the Courtyard line and the Assembly line or edge of the slot hole. You can clear the measurement results using Shift+C.
Let’s add a Component Center layer for component center designations.
Open the View Configuration panel. Right-click on any layer in the Layers region then select Add Component Layer Pair. Select Component Center in the Layer Type drop-down menu. Click OK to add a new layer pair. The All Layers region should look like the figure below.
Make the Top Component Center layer active. Using Place > Line from the main menus, draw a crosshair of lines in the center of the component.
The next step is to add the 3D model to the footprint. It is possible to connect a 3D model to the component in .step, PARASOLID, or .sldprt format. It is strongly recommended to add a 3D model for each component. This will offer more precise height rule matching, more pleasant PCB visualization, and a more accurate view while designing the assembly drawing in Draftsman. Let’s connect a 3D model to the footprint.
Download the .step model from here and place it in an appropriate location.
Open the View Configuration panel. Right-click on any layer in the Layers region then select Add Component Layer Pair. Select 3D Body from the Layer Type drop-down menu. Click OK to add a new layer pair. Make the Top 3D Body layer active.
Select Place > 3D Body from the main menus then select the .step model downloaded in step 26. Place the 3D model onto the workspace then select it. In the Properties panel, set the (X/Y) coordinates as -3.35mm and -2.1mm and define the Standoff Height as 1.2mm. In the design space, press the 3 key to switch to 3D mode and to verify the correct placement of the model. Save the footprint by pressing Ctrl+S then close the tab.
In the component editor, a footprint corresponding to the component appears in the Models region. Select File > Release to server from the main menus. Enter First component release in the Release Notes field then press OK. After a successful release, the GSB343K33HR tab will close and it will appear in the server and be ready for interaction for all workspace users.