Sometimes you will find a part you have never seen before and you are not familiar with its shape and land pattern. How can you incorporate it in your PCB design? After reading this article, you will know the steps to take to incorporate any IC package into your PCB design.
Let’s say we have an IC, like the BSC010NE2LSIATMA1, an N-Channel 25V 38A (Ta), 100A (Tc) 2.5W (Ta), 96W (Tc) Surface Mount PG-TDSON-8-7 device.
You can use two methods to design the PCB land pattern for this part.
Method 1 – Create the Part from the Part Data Sheet
Step 1. Find the part measurements in a data sheet
- Scroll to a section that shows “Recommended Land Pattern” or “Layout”, or some indicator of PCB layout, even part dimensions. For example, this part doesn’t have a land pattern recommendation but a data sheet will always have dimensions for a part.
- (If the manufacturer has a layout section for the part) Note the units for the data sheet.
Step 2. Extract the Measurements from the data sheet
- Take down the measurements the data sheet.
- Then put the measurements:
- on a piece of paper and redraw the part, or
- in a spreadsheet with a screen shot of the part or
- a screenshot that has the measurements overlayed on the part image
Step 3. Build the part using a PCB part creation tool (like the PCB Editor Package Symbol Creator or Package Symbol Wizard if you’re using Cadence Allegro.)
- Dimension, and input measurement guidelines first for a land pattern that are appropriately sized to mount the part onto the PCB.
- Build the part based on the measurements.
- Measure the footprint you just built and see if it matches the data sheet and gives enough room for a land pattern that’s guided by the part’s dimensions.
Once you have finished creating your part’s land pattern, save it with an IPC-approved name. Done.
Method 2 – Download the Part’s Footprint / Land Pattern
Go to the part’s page (for example, Digi-Key). See if they have a ‘CAD model’ associated with the part.
If such a model exists, download the footprint for any PCB design software you want.
Be sure to measure the footprint dimensions (and double check for appropriate solder mask clearance) for the part you downloaded.
If it all looks sensible for that part, you are done.
If you find a part that doesn’t come pre-installed with your OrCAD / Allegro software, know that the PCB Editor package symbol editor gives you maximum freedom to build footprints. Regardless of the part, you can create a footprint any time you need to and add it to your PCB design.