Deciphering Footprint Naming (Part 1)

June 5, 2018admin

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 HeightPin 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, [http://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

 

 

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