Coming soon to a PCB near you...

-April 15, 2014

Since all the easy/obvious applications are already done what's next in the PCB design front? After all, we have had PC-based PCB layout tools since the late 1980s, and while layer counts have increased and parts have gotten much, much smaller (0201s anyone?), those old PCB tools would still pretty much work today. Smaller parts? No problem, just zoom in more (Figure 1).

Figure 1: Even if these 0402 parts should shrink by 10X in a few years, this is not a problem for the basic PCB view of the world. We will just zoom in more and keep working away.

Opportunity Arrives
Where the opportunity lies in PCB tools as in all applications is integrating more and more of the design workflow into the primary PCB tool. Years ago we designed a PCB and the enclosure by hand. Then we went to 2D CAD systems like AutoCAD for the mechanical design, then 3D CAD tools arrived and we found ways to export a 3D Model of the PCB. This was a big improvement to be sure but the integration went the wrong way in my mind – we needed the integration back in the PCB design tool, which is just really starting to happen now [1].

The first more-or-less universal 3D capability was the IDF format files (Intermediate Data Format) (Figure 2) [1]. This was a good start and definitely a lot of component height checking can be done with this; but front panel fit can't be done due to the coarse, extruded, box-like nature of the part representation.

IDF files also did not allow for the proper integration of the workflow from the PCB designers standpoint; that is, we still could not manipulate the 3D shapes inside our PCB design tool. Most tools do not implement IDF capability in their main workflow, and the ones that try do it by launching a viewer.

Figure 2: A typical IDF file output; yes, the height info is there, but PCBs don't really get used in "Extruded Worlds" - the world is 3D. Also limiting the usefulness was the requirement of opening the IDF files in an external Drafting program or add-on viewer.

So what is really needed can be summed up as: Real 3D drafting integrated directly with the PCB design tool. Altium has had that capability for some time and others appear to be working toward it [2]. Figure 3 shows the same PCB as was rendered by IDF files in Altium's integrated 3D system.

Figure 3: A true 3D rendering of the same PCB as shown in Figure 2 above but with real Step Models attached to the footprints in the library.

This is what is really needed – true real-time 3D. Altium switches back and forth between modes with a key press, parts can be positioned in either view. This isn't just pretty, but increases productivity also as we will see.

I work on a lot of projects where I am also the "De-Facto" Packaging Engineer and frankly, except for some 2.5D AutoCAD-like tools, I don't run full 3D drafting packages. What this native PCB tool 3D capability gives me is a way to reduce the design errors and subsequent redesign cycles that happen during a design when mistakes are made. And that quickens time to market and reduces development costs.

Almost all component and enclosure manufacturers are making available 3D STEP models of their parts available. This in my view is most important for connectors and any part that interfaces with mechanical housings; and the mechanical housings themselves are becoming more and more available to.

With accurate STEP models we can see how the connectors mate up to each other before any hardware is built. This really reduces the chances of making errors. In Altium's case. even if the STEP models are not available they have simple 3D shapes (arbitrary rectangles, cylinders, spheres, etc.) that can be used to make a decent mechanical representation of any part rather quickly (Figure 4).

Figure 4: Here a 3D model of an edge launch connector was not available (Gold colored part), but I was able to draw one using simple shapes provided in Altium. The resulting model may not be polished, but it is dimensionally correct and can allow clearance checking with mating parts of the system.

The real power comes in being able to assemble all the pieces in one tool, the PCB tool, and actually see how things fit together (Figure 5 and 6). This is a trend that seems to be accelerating and is good news for all of us who use these front-end design tools. Also with full 3D integration is the ability to export a very good STEP model of the PCB to subsequent Mechanical or Packaging engineering as these process steps are still needed for complex designs where it just gets to be too much for the PCB tool to handle.

Figure 5: Allowing a full assembly to be viewed before hardware is built used to be only in the realm of Mechanical Design Packages; by pushing some of this capability to the PCB design tool allows instant feedback before the design proceeds.

Figure 6: Clearances and alignment can be checked in the Altium PCB design tool in real time as shown here by viewing a Ribbon connector through a panel and confirming that a Trimpot adjust actually lines up with the adjustment hole. Having this capability reduces the chances of making a mistake when the hardware gets built.

Visual Design Intent
I have also used the 3D capabilities on multi-engineer/multi-PCB assemblies. Here is is important to be able to present how everything will fit together so that the whole team can visualize the real design intent and see how their board fits into the entire system. This is very hard to do with flat drawings of PCBs; but when the entire team can see how everything is supposed to fit together when finished, it helps to reduce misunderstandings and keep the schedule on track.

Bottom Line
The bottom line is that this capability pushed into the design tool is a real time boost to productivity. Other opportunities for improvement that some, but not all, PCB design packages implement are:

  • Integrated 3D Drawing Capability
  • Real Integrated 2.5D Signal Integrity
  • Real Integrated Thermal Analysis

I add the note "Real" means a real simulation, not just some 1st-order approximations that many PCB programs implement. "Integrated" means it is in the main package - not some external viewer or third party add-on; this is especially important for 3D drawing.

References:
[1] IDF File Specifications, https://www.simplifiedsolutionsinc.com/images/idf_v30_spec.pdf

[2] Altium Designer has incorporated a true 3D design environment and 3D import / export capability since 2007. www.Altium.com
Cadence/OrCad has integrated 3D library support http://www.cadence.com
Mentor PADS has a 3D roadmap http:www.mentor.com

[3] STEP File Format, http://en.wikipedia.org/wiki/ISO_10303

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