Henry Ford once quipped that "Any customer can have a car painted any color that he wants, so long as it is black." With all due respect to the great automaker and production innovator, variety is, in fact, the spice of life. And just imagine how difficult entertaining the kids on road trips would be if we couldn’t guess all the different types of cars. However, with variety comes the responsibility of choice.
The ever-increasing use of electronic circuit boards has resulted in smaller, more capable PCBA and electronics products and more SMT component options. Consequently, building PCBAs is transforming to meet these demands and achieve heightened efficiency, quality and reliability. Since component selection represents a highly significant design decision impacting nearly every aspect of board manufacturing, you should know how your choice of surface mount package sizes affects board assembly.
Classifying Surface Mount Packages
Compiling a comprehensive list of different surface mount components and their sizes would be a staggering undertaking. Nearly all electronic components—passive, active, discrete, integrated or exotic—are available in one or multiple surface mount package types and/or sizes. Moreover, the package defines the component size, footprint and pad that influence the PCB layout routing, board size and specifications.
Instead of trying to list out every single SMD package, we’ve compiled a list of common SMD packages and sizes below.
Surface Mount Package Types and Sizes
- Discrete Components
Discrete SMD passive components are available in standard packages.
- Resistors, Capacitors, Inductors.
- Sizes (l x w): 0.4mm x 0.2mm to x 6.3mm x 3.2mm
- Flat Packs
Flat packs are typically square or rectangular and have the same number of pins on opposite sides of the package.
Pins extend from the package and attach to pads on the board surface.
Quad Flat Pack (QFP), Thin Quad Flat Pack (TQFP).
- Sizes vary according to the number of pins and pitch.
Pins are located on the underside of the package and attach to pads underneath.
Dual Flat Pack, No Lead (DFN), Quad Flat Pack, No Lead (QFN).
- Sizes vary according to pin number.
- Grid Arrays
Grid arrays have pins or balls arranged in columns on the underside of the package.
- Ball Grid Array (BGA), Land Grid Array (LGA).
- Sizes depend on the number of pins or balls, which exceed 500 for Super Ball Grid Arrays (SBGAs).
- Outline Packages
Small outline packages are typically low profile (height) components available as alternatives to through-hole dual inline packages (DIPs).
- Small-Outline Package (SOP), Thin Small-Outline Package (TSOP), Small-Outline Integrated Circuits (SOICs).
- Sizes vary greatly depending on the number of pins.
As indicated above, surface mount package sizes vary greatly depending on the type and number of external connections required. And the package you opt to use has significance throughout the development process, especially for your board’s assembly.
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How Surface Mount Package Size Impacts PCBA
The surface mount package(s) you choose for your design directly affects your board layout, construction and assembly. Therefore, you should make informed decisions that include these considerations:
Considerations for Selecting SMDs
- Trace Routing Requirements
Pin size, pitch, and footprint pads vary among surface mount package types. However, all of these, as well as current carrying requirements, affect trace size and weight.
- Clearance and Spacing Requirements
For PCB assembly, adequate clearances and spacing between board elements and with the board edge are critical for achieving high-quality solder connections.
- Solder Masking Concerns
Solder masking is performed during board fabrication; however, in addition to protecting the board surface against oxidation, solder masking supports assembly by providing a barrier that prevents solder bridging and other unwanted connections.
- Via Choices
PCB drilling is also a fabrication process. However, drill hole numbers, types and locations are important for assembly as components must be accurately aligned with the board’s vias.
- Accessibility for Testing
Another important concern when using SMT is design for testing (DFT) requirements. Functionality testing, which may be performed during PCBA, requires pin access that is not available for flat packs with no leads and gate array SMDs.
|Tempo's Custom PCB Manufacturing Service
The importance of component selection for PCBA development cannot be overstated. Consequently, for boards that include SMD components, be sure to include the considerations listed above in your selection process. Tempo Automation, the industry leader for fast, high-quality PCBA manufacturing, employs a smart software-based assembly process to optimize your board’s manufacturing.
And to help you get started on the best path, we furnish information for your DFM checks and enable you to easily view and download DRC files. If you’re an Altium Designer or Cadence Allegro user, you can simply add these files to your PCB design software. For Mentor Pads or other design packages, we furnish DRC information in other CAD formats and Excel.
If you are ready to have your design manufactured, try our quote tool to upload your CAD and BOM files. If you want more information on surface mount package sizes and how your SMD choices impact your board’s development, contact us.