Deciphering Footprint Naming (Part 1)
Some designers on SnapEDA have mentioned that they would like to better understand the naming convention we use for footprints, so we’ve created this blog post as a handy reference.
We build our footprints (also known as land patterns), to the IPC-7351B standard, with some exceptions. As such, we follow the naming convention defined in this standard for any new libraries we build. Naming conventions facilitate better communication between engineers to make the design process more efficient, so we believe they are essential. In this post, we’re going to explain how to decipher this naming convention, and how you can adopt it for your own libraries.
As with most standards, there are benefits and limitations to any convention or standard. But we believe this is the best naming convention in the industry (outside the soon-to-be-released IPC-7351C). For this reason, we make some adaptations to the standard in our processes (when needed) to account for those limitations. For example, there could be many thin quad flat packages (TQFPs) whose dimensions only differ by the size of the thermal pad at the center. Since the naming convention does not account for such an edge case, we have extended upon the standard to account for such cases.
Surface Mount Naming
In the IPC-7351B naming convention, every land pattern has its own convention based on its unique attributed. Let’s take a look at a QFP package as an example. The convention says it should be written as:
QFP + Pitch P + Lead Span L1 X Lead Span L2 Nominal X Height – Pin Qty + Suffix
The orange items denote the variables – in this case the pitch, lead span, height, and number of package pins. Additionally, there is an environment condition at the end of the name, to specify the density of the land pattern. At SnapEDA we use nominal by default, although we can support other densities as well. A very dense design might want to use the “L” least condition to make the pad size smaller, or “M” most to make the pads bigger for more rugged or industrial applications. The convention is included below for reference.
The dimensions are defined using the metric system. In some cases, Imperial (inch) units may be used in the land pattern name. This is done to reduce confusion between the metric dimension and the commonly used industry name. There may also be underscores ( _ ) used occasionally as a separator between the pin quantity in hidden and the deleted pin components.
Example: Naming a BGA Footprint
Let’s take a look at an example. In this case, we’ve created a BGA footprint for the MAX77816AEWP+T footprint and would like to name it. Referencing the naming convention below, the structure should be:
BGA + Pin Qty + C or N + Pitch P + Ball Columns X Ball Rows _ Body Length X Body Width X Height + Suffix
In this case, this part has 20 pins, has non-collapsing balls, has a 0.4 mm pitch, has 5 ball columns and 4 ball rows. Additionally, the dimensions are 5x4x0.69 mm. Assuming we follow the nominal conditions, the name would be:
BGA20N40P5X4_212X182X69N
Hope that helps explain the naming for surface mount components. In part 2 we’ll cover the naming for through-hole components!
References: Surface Mount Land Patterns Subcommittee (1-13) of the Printed Board Design Committee (1-10) of IPC, Generic Requirements for Surface Mount Design and Land Pattern Standard, [https://shop.ipc.org/IPC-7351B-English-D ]
| Ball Grid Array’s | BGA + Pin Qty. + C or N + P Pitch _ Ball Columns X Ball Rows _ Body Length X Width X Height + B Ball Diameter |
| BGA w/Dual Pitch | BGA + Pin Qty. + C or N + P Col Pitch X Row Pitch _ Ball Columns X Ball Rows _ Body Length X Width X Height + B Ball Diameter |
| BGA w/Staggered Pins | BGAS + Pin Qty + C or N + Pitch P + Ball Columns X Ball Rows _ Body Length X Body Width X Height |
| Capacitors, Chip, Array, Concave | CAPCAV + Pitch P + Body Length X Body Width X Height – Pin Qty |
| Capacitors, Chip, Array, Flat | CAPCAF + Pin Qty. + P Pitch _ + Body Length X Width X Height + L Lead Length X Width |
| Capacitors, Chip, Non-polarized | CAPC + Body Length + Body Width X Height |
| Capacitors, Chip, Polarized | CAPCP + Body Length + Body Width X Height |
| Capacitors, Chip, Wire Rectangle | CAPCWR + Body Length + Body Width X Height |
| Capacitors, Molded, Non-polarized | CAPM + Body Length + Body Width X Height |
| Capacitors, Molded, Polarized | CAPMP + Body Length + Body Width X Height |
| Capacitors, Aluminum Electrolytic | CAPAE + Base Body Size X Height |
| Ceramic Flat Packages | CFP127P + Lead Span Nominal X Height – Pin Qty |
| Column Grid Array’s | CGA + Pitch P + Number of Pin Columns X Number of Pin Rows X Height – Pin Qty |
| Crystals (2 leads) | XTAL + Body Length X Body Width X Height |
| Dual Flat No-lead | DFN + Body Length X Body Width X Height – Pin Qty |
| Diodes, Chip | DIOC + Body Length + Body Width X Height |
| Diodes, Molded | DIOM + Body Length + Body Width X Height |
| Diodes, MELF | DIOMELF + Body Length + Body Diameter |
| Diodes, Side Concave | DIOSC + Body Length X Body Width X Height – Pin Qty |
| Fuses, Molded | FUSM + Body Length + Body Width X Height |
| Inductors, Chip | INDC + Body Length + Body Width X Height |
| Inductors, Molded | INDM + Body Length + Body Width X Height |
| Inductors, Precision Wire Wound | INDP + Body Length + Body Width X Height |
| Inductors, Chip, Array, Concave | INDCAV + Pitch P + Body Length X Body Width X Height – Pin Qty |
| Inductors, Chip, Array, Flat | . INDCAF + Pitch P + Body Length X Body Width X Height – Pin Qty |
| Land Grid Array, Circular Lead | LGA + Pin Qty + C + Pitch P + Pin Columns X Pin Rows _ Body Length X Body Width X Height |
| Land Grid Array, Square Lead | LGA + Pin Qty + S + Pitch P + Pin Columns X Pin Rows _ Body Length X Body Width X Height |
| Land Grid Array, Rectangle Lead | LGA + Pin Qty + R + Pitch P + Pin Columns X Pin Rows _ Body Length X Body Width X Height |
| LED’s, Molded | LEDM + Body Length + Body Width X Height |
| LED’s, Side Concave | LEDSC + Body Length X Body Width X Height – Pin Qty |
| Oscillators, Side Concave | OSCSC + Pitch P + Body Length X Body Width X Height – Pin Qty |
| Oscillators, J-Lead | OSCJ + Pitch P + Body Length X Body Width X Height – Pin Qty |
| Oscillators, L-Bend Lead | OSCL + Pitch P + Body Length X Body Width X Height – Pin Qt |
| Oscillators, Corner Concave | OSCCC + Body Length X Body Width X Height |
| Plastic Leaded Chip Carriers | PLCC + Pitch P + Lead Span L1 X Lead Span L2 Nominal X Height – Pin Qty |
| Plastic Leaded Chip Carrier Sockets Square | PLCCS + Pitch P + Lead Span L1 X Lead Span L2 Nominal X Height – Pin Qty |
| Quad Flat Packages | QFP + Pitch P + Lead Span L1 X Lead Span L2 Nominal X Height – Pin Qty |
| Ceramic Quad Flat Packages | CQFP + Pitch P + Lead Span L1 X Lead Span L2 Nominal X Height – Pin Qty |
| Quad Flat No-lead | QFN + Pitch P + Body Width X Body Length X Height – Pin Qty + Thermal Pad |
| Pull-back Quad Flat No-lead | PQFN + Pitch P + Body Width X Body Length X Height – Pin Qty + Thermal Pad |
| Quad Leadless Ceramic Chip Carriers | LCC + Pitch P + Body Width X Body Length X Height – Pin Qty |
| Quad Leadless Ceramic Chip Carriers (Pin 1 on Side) | LCCS + Pitch P + Body Width X Body Length X Height – Pin Qty |
| Resistors, Chip | RESC + Body Length + Body Width X Height |
| Resistors, Molded | RESM + Body Length + Body Width X Height |
| Resistors, MELF | RESMELF + Body Length + Body Diameter |
| Resistors, Chip, Array, Concave | RESCAV + Pitch P + Body Length X Body Width X Height – Pin Qty |
| Resistors, Chip, Array, Convex, E-Version (Even Pin Size) | RESCAXE + Pitch P + Body Length X Body Width X Height – Pin Qty |
| Resistors, Chip, Array, Convex, S-Version (Side Pins Diff) | RESCAXS + Pitch P + Body Length X Body Width X Height – Pin Qty |
| Resistors, Chip, Array, Flat | RESCAF + Pitch P + Body Length X Body Width X Height – Pin Qty |
| Small Outline Diodes, Flat Lead | SODFL + Lead Span Nominal + Body Width X Height |
| Small Outline IC, J-Leaded | SOJ + Pitch P + Lead Span Nominal X Height – Pin Qty |
| Small Outline Integrated Circuit, (50 mil Pitch SOIC) | SOIC127P + Lead Span Nominal X Height – Pin Qty |
| Small Outline Packages | SOP + Pitch P + Lead Span Nominal X Height – Pin Qty |
| Small Outline No-lead | SON + Pitch P + Body Width X Body Length X Height – Pin Qty + Thermal Pad |
| Pull-back Small Outline No-lead | PSON + Pitch P + Body Width X Body Length X Height – Pin Qty + Thermal Pad |
| Small Outline Transistors, Flat Lead | SOTFL + Pitch P + Lead Span Nominal X Height – Pin Qty |
| SOD (Example: SOD3717X135 = JEDEC SOD123) | SOD + Lead Span Nominal + Body Width X Height |
| SOT89 (JEDEC Standard Package) | SOT89 |
| SOT143 & SOT343 (JEDEC Standard Package) | SOT143 & SOT343 |
| SOT143 & SOT343 Reverse (JEDEC Standard Package) | SOT143R & SOT343R |
| SOT23 & SOT223 Packages (Example: SOT230P700X180-4) | SOT + Pitch P + Lead Span Nominal X Height – Pin Qty |
| TO (Generic DPAK – Example: TO228P970X238-3) | TO + Pitch P + Lead Span X Height – Pin Qty |
