Sometimes 2 + 2 does NOT equal 4, sometimes the combination of two technologies can amplify the benefits of both to something far greater. Today’s blog is going to shine a light on the combination of using both flexible materials and ultra-HDI feature sizes, specifically, trace and space that is less than 50 microns and in fact is now being produced in the United States with 20-micron trace and space using traditional printed circuit board fabrication equipment.
First, because this is a relatively new term, the definition of Ultra-HDI, per IPC’s recently established working group is a design that includes one or more of the following parameters:
Ultra-HDI is currently being offered by PCB fabricators with circuit trace and space as tight as 20 micron and 12.5 micron is expected to be available later this year.
Even if we don’t push the boundary all the way to 12.5 micron, using a 25-micron trace and space has several benefits:
Looking at even just the first two to three benefits of each technology, one can see the overlapping benefits. Flexible materials help solve a packaging issue and GREATLY reduce size and weight. Ultra-HDI technology has similar benefits. Moving from a 75-micron trace to a 25 micron trace allows the printed circuit board designer to either significantly reduce the overall size of the flexible circuit board or reduce the number of routing layers necessary to make connections.
I don’t think it is any stretch of the imagination to envision the significant benefits to size and weight when incorporating both flexible materials and ultra-HDI feature sizes, replacing traditional rigid materials with circuit trace and space created with subtractive etch technology.
Bonus: If the A-SAP™ process is selected to create the Ultra-HDI features, this process is done by etching away all copper and adding metal back to create the conductor pattern. Polyimide and LCP materials are often selected for Bio-compatibility reasons. The A-SAP™ can create conductor patterns with gold and other noble metals eliminating all copper and nickel from the process creating a unique biocompatible solution.
These ultra-HDI techniques are changing the way PCB designers look at solving complex design issues. If you are interested in learning more about SAP processes, please refer to a few of our previous blogs. We have gone through the basics to SAP processing, recently looked at some of the top questions related to the printed circuit board stack up and explored the design space around the possibility of utilizing these ultra-high density circuit trace widths in the BGA escape regions and wider traces in the routing field. The benefit is a reduction in circuit layers and the concern is maintaining 50-ohm impedance. Eric Bogatin recently published a white paper analyzing just this benefit and concern.
Please reach out with your questions about Ultra-HDI or flexible circuit technology!