Should the ground connections share vias?

Just like it says "on the tin," wafer-level chip-scale packaging (WLCSP) is a technology that shrinks the substrate down to a size quite close to that of the actual silicon, gallium arsenide or whatever material makes up the die. Rather than calling it a substrate, the WLCSP material is known as a redistribution layer, or RDL for short. It's a subtle but important distinction.

By definition, WLCSP devices exclude wire bonding, leaving flip-chip technology as the method of die attach. That means that there is no die cavity where a solid ground plane on the bottom of the die would normally act as the mating surface. Instead, the chip is mounted face down with BGA-style balls on a pitch that is typically less than 0.5mm. Right there, the challenge can be to maintain a good thermal path through the tiny connections (Figure 1).

The solution is to have numerous ground balls to help dissipate thermal energy. The ground balls can be distributed around the device or gathered into a central square or rectangle, maybe both. Either way, it's best if every one of the ground connections gets a dedicated via rather than combining them to share a via.

Durability in the heavens can lead to sustainability on Earth.

We are increasingly reliant on satellite-borne services, as evidenced by the huge increase in launches in the past few years. The United Nations Office for Outer Space Affairs (UNOOSA) has recorded over 5,500 launches between 2020 and 2022 in its Register of Objects Launched into Outer Space. This contrasts with typically 100 to 200 per year from the early 1960s until 2016.

The vast majority of satellites in operation today support communication applications such as Internet services. Of the 6,718 operational satellites at the start of 2023, 4,823 are communication satellites. While their number has increased more than 50% since 2022, there are also over 1,200 Earth observation satellites, up by more than 13%. Others are used for technical development, navigation and positioning, and space observation.

We need the services these space vehicles provide. The Starlink constellation, delivering high-speed Internet services, operates in a low earth orbit at an altitude of about 550km. It can boast much lower latency than typical Internet satellites in higher, geostationary orbits needed to support streaming services and video calls. This enables high-quality services to reach areas where installing ground-based Internet infrastructure is not cost-effective or practicable.

Over-the-top security controls can do more harm than good.

Is the bureaucracy of security making us all less secure? That is a question I find myself asking increasingly as layer after layer of bureaucracy in the form of forms, protocols and additional steps makes quoting, receiving orders, building product and then shipping and invoicing more cumbersome and time-consuming.

Don't get me wrong: I believe in quality and security, especially in the world we are living in and with the cyber-reliant environment we must utilize to communicate and share data among people and businesses. Increasingly, however, some measures that are intended to increase security instead have the effect of wasting time, adding cost and extending lead times to deliver much-needed product.

Prepare yourself for unusual circuit patterns.

There is no free lunch when it comes to populating a printed circuit board. Every part has a cost and a failure rate. One of the first projects of my career was a pulse-Doppler surveillance radar called PSTAR. In typical military jargon, that acronym stands for “Portable Search and Target Acquisition Radar.”

My part was the amplifier module that was subdivided into various blocks for easy field service. One of the sub-blocks was a 20dB coupler. It lived inside its own hermetically sealed aluminum housing. The PCB inside had two traces that ran alongside each other, giving the circuit four ports with feedthroughs to the outside world. SMA connectors and semi-rigid cables wired the various modules together.

My responsibilities included the little housing for the coupler, the overall mechanical packaging and all the semi-rigid cable drawings, as well as the RF amplifier. The control board was the only part designed by an external vendor. Meanwhile, the PCB for the coupler had no more than a single 50Ω termination resistor and the feedthrough connectors. We did not yet have PCB design software at that company, so this was done with AutoCAD.