Leaning Tower of Pisa: An example of foundation imbalance

Best Techniques for Copper Thieving for PCBA Development

Italy is well known for the beauty and uniqueness of its architecture. Structures like the Colosseum and the Sistine Chapel are awe-inspiring. In terms of uniqueness, however, few buildings can match the Leaning Tower of Pisa. Although its attractive design was a cultural mainstay back in the day, today, this bell tower is more famous for its unbalanced foundation that gives the impression it may someday fall over.

Making similar mistakes while constructing PCBs can lead to problems much more severe than a lopsided appearance, including degradation of structural integrity, reduced signal integrity, and increased manufacturing costs. One way to avoid these issues is to employ copper thieving for PCBA development, which is best implemented alongside proper designer and CM collaboration.

What is Copper Thieving?

Copper thieving is a bit of a misnomer. The process actually adds copper to the board surface, often in the form of a matrix of dots as shown below.

Example of adding copper thieving for PCBA development. From electronics stack exchange.

Example of adding copper thieving for PCBA development. From electronics stack exchange.

The shapes may vary; for example, squares or triangles may be used instead of dots. Nevertheless, these elements are added to the surface or inner layer in areas where minimal copper exists.

Why is Copper Thieving Used?

The first steps of PCBA manufacturing comprise the fabrication stage. During this stage, the bare board is created. Here, the traces, component pads, and other areas of the PCB layout where copper is required are exposed by etching—the removal of preexisting copper from both the surface and inner layers. Depending on the board design, these areas may not be well distributed over the layer, which is a primary reason for adding copper to the layout. Specific motivations for copper thieving for PCBA manufacturing are listed below.

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Reasons to use copper thieving for PCBA manufacturing

  • To control board dielectric
    An important consideration for electronic circuit board design is impedance management, which is done by choosing dielectric materials. For high-speed boards, controlling impedance—or dielectric constant—is crucial for maximizing signal integrity and controlling board thickness.
  • To prevent structural integrity compromise
    If your board build contains uneven copper layers, the likelihood of deformations increases. These deformations, such as twists and bows, can significantly compromise structural integrity.
  • To prevent over etching and plating
    Over etching on inner layers and/or over plating on surface layers results from a lack of copper in certain board areas compared to others. This may result in excess costs if left untreated.

Ultimately, the goal of copper thieving is to provide balance to your board layout. This is best achieved by following a few simple guidelines as discussed below.

How Best to Implement Copper Thieving for PCBA Development

Optimization for most custom PCBA designs requires several iterations to achieve the highest quality. This not only places a premium on iteration speed, but also on the level of collaboration between the designer and CM. The effectiveness of this collaborative effort depends on the designer incorporating the CM’s DFM rules and guidelines and on the CM incorporating the design intent throughout the board build process. This includes copper thieving for PCBA development.

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Ideally, copper thieving is not used, as all copper layers are sufficiently balanced to avoid manufacturing quality risk. When necessary, copper thieving is best utilized when the engineer or designer clearly stipulates where in the layout of the design file package it can be used. As with other manufacturing decisions, it’s good practice to leverage your CM’s expertise and judgement to define the exact specifications for reliability and structural integrity. At Tempo Automation, we utilize a smart digital thread manufacturing process that’s based on transparency to ensure design intent is always maintained.

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 CAD files or how to incorporate your design into a CAD format, contact us.

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