The Ware for August 2009 is the Viking Lander Command Detector Board (VCLD). The Viking Landers were robotic probes sent to Mars in the 1970’s. The board itself dates from 1970.

The Ware was submitted by Norman Yarvin, and fortunately, the original author of the report on the circuit board, Bob Schuster, was in the loop to explain what it did, and how it was made.

Some notes from Bob Schuster:

The big round thing in the lower right hand corner was an xtal used in the bit timing oscillator.

The larger empty rectangular space on the lower left was for a voltage controlled xtal oscillator used in the subcarrier recovery circuits.

Most of the components used were already 5 or more years in vintage, there were “better” parts, but we were using only established reliability parts.

A very detailed, and quite interesting, report summary was written by Bob, that explains the design approach behind the board and how it worked. Here’s an excerpt:

This board is one of two boards (primary & redundant) and was part of the Command Control Unit (CCU) a box that also contained power supplies and antenna control electronics-plus other stuff which I forget. It was flown on the Viking mission to Mars and was the first USA landing of a spacecraft on another planet. Its mission was imaging and the search for evidence of life.

NASA’s web site should be visited for more information about Viking.

Since its mission included a search for evidence of life all flight hardware on the Lander had to be sterilized in an oven at 254 degrees F (123deg C) for two days before it could be launched. It still had to function after the sterilization of course.

The board shown in the picture is the first Engineering Test Model (ETM) produced and that is why there are so many cuts and jumpers visible. The dust evident in the pictures (not very sterile) is from sitting around my attic these many years. I should have made it prettier but this was done on the spur of the moment.

The purpose of the board was to recover –- reliably — the digital data being up-linked to the Lander computer from earth. The computer could then be re-programmed as conditions changed or as mission scientist came up with new things to try. The emphasis on reliability was due to the low bit rate viz 4bits/sec and the limited time available each earth day to send reprogramming commands plus the long transit times for the radio signals to reach Mars (maybe about 3 to 4 sun earth transit times or about 4x9min=36 minutes ONE WAY. If the computer data had more than one error it could not correct it, or if the detector declared a poor subcarrier signal or bad bit timing the Lander was programmed to request a retransmission of the data from earth. This event triples the time to get data uploaded to about 1.8 hours! A bit error rate of 1bit in every 100000 bits was selected by systems engineering as an error rate the mission could live with. This would presumably keep code retransmission to a minimum thereby not burning up precious contact time. Given the available transmission power of the Goldstone Tracking station and the vast distances involved the S/N ratio was just sufficient to get to the error rate specified. If the error rate was not achieved then retransmissions episodes would get too numerous and the mission would be compromised. So the VLCD had to make maximium use of the available S/N and not degrade the signal in the data recovery process.

It’s amazing this was done in the early 70’s — years before PCs were introduced — and it’s advanced communications research similar to this that laid the foundations of the mobile phone networks that we take for granted today.

You can read the full summary report here (small — 40 kB). For those interested in the original history, I also have a PDF of some scans of the original pages (large — 3 MB) of the report typed up in 1971.

Oh, and the winner — a bit hard to pick since there were a lot of thoughtful comments; I’ll go with Wang-Lo. Even though I’m not quite sure the coax cables were used as part of a delay line differentiator, he did posit a guess that this was for the Viking spacecraft. Congrats, email me for your prize.

This month’s ware is pictured below. Click on the photos for a much larger version.

This month’s ware is a user-submitted ware. This ware doesn’t quite qualify as a “production” ware but it does qualify as a very interesting ware, partially because of its vintage and its relative sophistication. I’d be surprised if anyone out there could exactly identify what this ware is, but I’m thinking someone out there can at least name the general function and origin of this ware…when I name the winner I’ll post some interesting details about the ware!

Well, that last ware was surprisingly easy to guess. I have a couple more blank PCBs I’m going to try in the future, they should be a little more difficult to guess — they don’t have any keyboard lands to help with identifying the design. Still, I’m impressed that people figured it out so quickly. I’m convinced by johnny ^_^’s guess that it’s an HTC Touchpro 2, so he’s the winner! congrats, email me to claim your prize!

The Ware for July 2009 is shown below. Click on the image for a much larger version.

I thought I’d try something new for this competition. Above is a scan of a completely blank PCB. I don’t actually know what it’s from. I just bought it from a vendor in the Shenzhen mobile phone market who also didn’t know what it’s from — it was just used for shop decoration to attract customers. Since I actually don’t know what it’s for, I’ll have to rely on the depth of your comments to convince me. If nobody can convince me, then there would be no winner. On the other hand, it’s quite possible I could choose a winner who incorrectly identifies the ware, but that’s ok — this game has always been more about explanation and sharing thought processes, rather than about absolute accuracy.

I do think a blank PCB like this is fairly interesting to post for a number of reasons. First of all, it gives you a real appreciation for the sheer density of routing on a mobile phone motherboard. Second of all, this is a great example of an HDI-buildup, blind/buried via PCB. If you look at the large version of the scan, you can see the dimples where they used a laser, instead of a drill, to cut tiny vias into the outer layers of the circuit boards. There are almost no through-holes, and via-in-pad (typically forbidden when using through-hole vias) is very common in this design. Finally, this pair of PCBs is actually still in its manufacturing frame, which reveals a number of test structures that you never see (visible on the right hand side) that are used to verify that the PCB’s construction is correct.

You can also see in here how the two copies of the board are inverted across the horizontal mid-plane. I’m not 100% sure why they do this, but I suspect it has to do with balancing throughput on the SMT line. One side of the PCB is very dense with components and the other side isn’t. Since the board has components on both sides, you will have to flip the board over at least once to process each side. On high-throughput SMT lines, this means that you’ll have two (expensive) SMT pick/place (or chip shooting) machines back to back, one to handle the top, and the other to handle the bottom after flipping. If you have both boards top-side up, then the SMT machine handling the denser top side would run much longer than the one handling the sparser bottom side, and you would effectively be idling one machine for a relatively long period of time. This would increase the amount of capital you have to spend to scale your production line and require greater amortization for a given throughput, ultimately driving up product cost (or reducing your net profit). Mirroring the board about a central axis also allows you to use the exact same programming for the two back-to-back SMT machines (separated by a robotic flipping mechanism) so you only have to optimize one SMT program, although at the expense of possibly having to incorporate a greater mix of parts within a single SMT machine.