Do you remember the hype on EP’s (Embedded Passives) just a few years ago?
In the PCBD&F magazine, late in 2006, Kathy Nargi-Toth wrote in an Editorial to PCD&F referring to an industry survey:
The statistic that blew me away was the change in anticipated implementation of embedded passives.
The projections are that 24.6% of the PCBs, up 222% over current figures, will incorporate embedded components. Are we on the brink of widespread acceptance? …”
While quite a few companies do use EP’s I’m sure we can agree that the boom indicated by the survey never happened!
Why is that? This technology was very promising with all the right market drivers.
What happened was that development caught up with a few of the market drivers:
An embedded resistor is small but not that small. While companies developed technology demonstrator designs with EP’s, the component manufacturers kept reducing the size of the surface mounted components dramatically –and delivered parts with better tolerance than is achievable with EP’s without laser trimming. So, the size argument is gone.
Freeing outer layer board space:
While this one is still valid, smaller components makes it less critical. Interestingly, as the SMD parts are halved in size in every generation (sort of) the board surface they require doesn’t shrink at the same rate as we need some space for assembly machinery and the solder pads need to have certain sizes.
Still, if you really need to gain outer layer space, you can actually embed smaller SMD components in the PCB laminate.
OK, so here is one driver that still applies –big time! As signal speeds goes up it becomes critical to manage parasitic and real EP’s have extremely small parasitic as they can be placed right at the pin they support –for example in high speed termination of a multi gigabit SERDES channel.
Also, when used as an embedded capacitance plane to eliminate or reduce the number of decoupling capacitors you are typically able to reach a much better power distribution network performance than when using discrete decoupling.
So, while several of the market drivers are gone, this is not true for all markets where drivers remains valid and drives use of EP’s in specific products.
For more information read my article in PCB Magazine: http://www.iconnect007.com/emag/pub/PCB-Nov2011/?page=66