Feature: Connectors
Modular design has become more popular, allowing key sub- sections such as I/O, processor and analogue signal processing to be built onto separate boards that can be re-used across several products
example, has become more popular, allowing key sub-sections such as I/O, processor and analogue signal processing to be built onto separate boards that can be re-used across several products. Tis reduces the design risk and development time and, through the combination of several smaller PCBs, offers more flexibility in addressing challenging formats. Still, careful consideration must be given to how to inter-connect the various modular boards.
Float on:
Board-to-board interconnects for modular design
By Ryan Smart, VP of Product, Harwin D
esign is a multi-faceted challenge. Not only are engineers expected to deliver products with higher performance and more features in ever- smaller forms, they must also complete designs in shorter times to remain competitive. In addition, there is a growing need for designs to
be manufactured at high speed, without compromising quality or operational reliability of a product in its lifetime. Meeting these requirements relies on both the design process and the materials and components selected. Modular design, for
28 May 2024
www.electronicsworld.co.uk
Single or multiple connectors Clearly there is a need for the boards in a modular design to reliably connect with each other, allowing signal and power movement between them. Whilst using a single connector between boards is relatively simple, in many cases this is not ideal. Firstly, it means that multiple types of signal (power, digital clocks, digital data and analogue) must pass through the same connector, which can introduce crosstalk and other noise. Secondly, all the PCB traces have to be routed to the connector. Apart from the space required, long traces can introduce noise and propagation delays that negatively impact circuit operation. For this reason – and especially on larger boards – a preferred
approach is to use fine-pitch interconnects comprising many pins across multiple connectors. Tis improves flexibility, reduces trace lengths and allows each type of signal to have its own dedicated contacts. However, with multiple board-to-board connectors deployed between a board pair, mechanical alignment and positional tolerance become urgently important. Precise placement on the PCB is critical, while the need for automated manufacturing demands that this placement be performed at high speed. Unfortunately, with two or more connectors mating the same two PCBs, the level of placement accuracy required oſten exceeds the parameters of even the best modern manufacturing processes. It is a problem because misalignment by even sub-millimeter distances – whether due to PCB manufacture, paste location, pick-and-place accuracy or a combination of these – will put undue stress (such as excessive side-loading) on the board-to-board connectors. In turn, this can cause damage, leading to quality and yield problems during manufacture and potentially reduced system reliability during its operation in the field.
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