Different surface mount resistor package sizes on PCBA

How to Best Utilize Surface Mount Resistor Package Sizes for Your Design

The word "optimum" or one of its derivatives—optimal or optimize, for example—is commonly used to describe something that is considered the best. Applying this term invites scrutiny, especially when attached to a tangible product or process. Yet, an optimal process or product can be proven, provided the factors on which this condition depends are clearly defined.

In mathematics, optimization typically takes the form of an objective function that must be minimized or maximized. This function is constrained, which defines the region where the optimization holds. This same strategy can be applied to PCBA layout design. For example, if the size of the board and the number of components are fixed, then surface mount resistor package size may be a significant factor for optimizing your board layout.

Surface Mount Resistor Package Size Options

Commonly used passive components, such as resistors and capacitors, play a significant role in optimizing your PCB layout design. However, you need to know the available size options.

Code Length (l) Width (w) Height (h) Power
Imperial Metric inch mm inch mm inch mm Watt
0201 0603 0.024 0.6 0.012 0.3 0.01 0.25 1/20 (0.05)
0402 1005 0.04 1.0 0.02 0.5 0.014 0.35 1/16 (0.062)
0603 1608 0.06 1.55 0.03 0.85 0.018 0.45 1/10 (0.10)
0805 2012 0.08 2.0 0.05 1.2 0.018 0.45 1/8 (0.125)
1206 3216 0.12 3.2 0.06 1.6 0.022 0.55 1/4 (0.25)
1210 3225 0.12 3.2 0.10 2.5 0.022 0.55 1/2 (0.50)
1812 3246 0.12 3.2 0.18 4.6 0.022 0.55 1
2010 5025 0.20 5.0 0.10 2.5 0.024 0.6 3/4 (0.75)
2512 6332 0.25 6.3 0.12 3.2 0.024 0.6 1

Resistance, tolerance, maximum current and power dissipation are major determinants when selecting resistors for operation and performance. For manufacturability, though, the most important considerations are where and how your resistors will be attached to the board.

Using SMD Resistor Selection for PCB Layout Optimization

Not only is component selection the first step for PCBA design, but it is also the most important decision because it impacts all of the stages of board development. This is especially true for your board build, as indicated by the list below.

Impact of Surface Mount Resistor Package Size on Board Design 

  • Spacing and clearances
    Maintaining sufficient spacing between board elements and clearance with the board edge is critical for manufacturing. For example, physical limitations influence how close pick-and-place machines can mount components. Moreover, placing components too close to the board edge can impact depanelization.
  • Solder mask
    Solder mask is a protectant applied to the board to guard against premature failure due to oxidation or other contamination. Where solder mask can be applied depends on the spacing between surface elements (like resistors), pitch of component pins and thermal considerations.
  • Trace routing
    When there are many similar components such as resistors on a board, it is advisable to use similar package sizes. This makes it easier to place and orient the components in the same direction to facilitate good solder flow and efficient routing.
  • Stackup and layer count
    As board sizes decrease, routing through resistors often necessitates the use of vias. Significant numbers of resistors may directly affect the number of signal layers in your stackup design.

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It may be tempting to simply choose the smallest SMD package for your resistors; however, that may not always be possible nor optimal. Instead, the best selection for your design should incorporate and balance the tradeoffs between PCB layout implications--including those listed above--and manufacturing considerations.

Tempo's Custom PCB Manufacturing Service
  • ISO-9001, IPC-600, and IPC-610 commitment to quality certifications.
  • Execute your full development cycle from proto to validation, NPI, and low volume production.
  • Accurate quote in less than a day.
  • Performs entire turnkey process in as fast as 4 days.
  • DFX support, including DFM, DFA, and DFT from Day 1 of design.
  • Sources components from the most reputable suppliers in the industry. to reduce procurement time.
  • Software-driven smart factory with monitoring and control throughout the manufacturing process.
  • Performs multiple automated inspections during PCB assembly to ensure PCB quality for prototyping.
  • Smooth transition from prototyping to production.

At Tempo Automation, the industry leader for fast, high-quality PCBA prototyping and on-demand production, our turnkey services include component procurement which can aid you in making selections that help facilitate the most effective building of your boards.

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 how to best select surface mount resistor package sizes for your board development, contact us.

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