Sierra Circuit Certification

The classification of connectors

An electronic system is a hierarchical interconnection network that enables communication among different electronic devices. Several interconnects are required for signal transmission and power distribution to ensure the correct operation of electric products. Electrical connectors are classified into three types with regard to their termination ends: board-to-board (B2B) connectors, wire-to-wire (W2W) connectors, and wire-to-board (W2B) connectors. The connectors are also classified based on the application like signal connectors, RF connectors, and power connectors. Signal connectors can be further classified as general-purpose, low-frequency, and high-frequency connectors such as USB, PCIe, etc.

Why choosing Sierra Circuits for
your PCB assembly

    1. 1. We do it all under one roof: design, manufacturing, assembly and component procurement. This makes us accountable from beginning to end. Before we send your design to fab, we take into consideration all the manufacturing and assembly processes so we know we will deliver a zero-defect board.

    1. 2. We offer quick turnarounds of 5 days or less. If you are in the bay area, you can even come pick up your boards yourself.

    1. 3. Our engineering team performs DFM and DFA checks to ensure the manufacturability of your board.

  1. 4. We offer a wide range of quality tests to make sure we ship a high-performance product. We perform cross-sections at every stage of the fab process and offer AOI, BGA X-ray and flying probe testing.

Challenges of incorporating connectors in a system

Increasing signal speed and switching frequency demands stringent requirements from connectors. Primary issues while dealing with connectors are electrical length, need of a larger assembly area, compatibility with new technologies, and reliability.

A connector introduces an extra electrical path that can lead to added propagation delay and electrical noise, such as crosstalk.

A connector also raises concern for reliability, because degradation of the contact interface can lead to an increase in contact resistance, resulting in signal distortion, heating problems, and power loss. These losses increase due to contact resistance, which depends on the material properties of the connectors, environmental conditions, and mode of operation.

Additionally, since a connector occupies more area than a simple solder or adhesive, the use of connectors might be difficult in applications that have limited space.


Ways to attach a connector to the PCB

When mounting a connector, it is important to know the influence of forces such as engagement, disengagement, and mounting methods such as pressing or soldering. The three mounting methods (shown in the above image) are frequently used in PCB applications. First is the press-in method, which means that the PCB connector with press-in legs is inserted into the defined plated-through holes. Compared to the traditional soldering method, press-in mounting guarantees the same electrical and mechanical performance. It also makes a more secure contact and is easier to assemble than with soldering.


How to achieve a good, reliable, and repeatable connector attachment

  • Choose the attachment method based on the application requirements (electrical, mechanical, and environmental).
  • If a tool is needed for assembling, carefully consider the advantages and disadvantages of the available tools.
  • Recommended tools are those with calibration sets and guaranteed repeatability. Follow the enclosed assembly instructions step by step.
  • Check the results carefully. If in doubt, consult the manufacturer for help.

PCB layout rules when designing with connectors

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    Place all connectors on one edge or on one corner of the PCB.

    Placing connectors on one edge of the board makes it much easier to hold them on the same reference potential. This is important for boards with high-frequency components that will not be shielded. 

    Some designs require connectors to be placed on different sides of the board. In such situations, it's critical to avoid placing high-frequency circuits between any two connectors. If it is not possible to avoid placing high-frequency circuits in between connectors, a metal enclosure and chassis ground filtering are employed to prevent the board from driving common-mode currents onto the connected wires. 

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    When a trace has a propagation delay of more than half the transition time of the signal it carries, then it requires matched termination.

    Don't use a matched termination unless the rise time has already been slowed as much as possible and the trace length has been shortened as much as possible. Matched terminations are undesirable because they use more power and make it difficult to control rise times. However, they are important for signal integrity and EMC when the trace delay is more than the transition time. You check out our trace width calculator which is capable of calculating trace width, the amount of trace current and the temperature rise.

Take a peek at what’s inside the design guide

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"Sierra makes it easy to place orders and offers quality and quick turn for our prototype boards."

Bruce Feige

CAD Operator/Supervisor, Ohio Semitronics, Inc
"You guys have the DFM checks that are really handy."

Herbert Gass
Design Engineer, Winduracnce LLC
"From getting a quote to placing an order, it was all very easy. The DFM/DFA check-in system worked pretty well."

Ryan Tullius
Design Engineer