In the #Badgelife: Tears for Tor Defcon Badges

Defcon 2019 has been and gone and hopefully, some of you managed to get your hands on one of these tear-jerking vegetables.

Tears of joy if you got one

Creator Seeess (name has no relation to Seeed, really), was the brainchild of this Sh*tty Add-On (SAO). Consisting of a total of 7 populated parts, the simple design is based on the ATTiny402 and is programmed with several LED modes and 2 hidden ones which are unlocked by playing some games with the LEDs.

Consisting of just a single push button, you can imagine the types of games playable on this handheld is somewhat limited. One involves a button-mashing minigame and a reaction game. 

Add a green tuft on top of this fella and you may be familiar with this particular purple onion from the Tor Project, those who brought you the open-source Tor browser that focuses on protecting the personal privacy of its users. To help with Tor’s fundraiser, Seeess spent his own time developing, coding and crimping these boards with nothing more than the intent of breaking even.

500 of these were available at Tor’s booth at this year’s Defcon, complete with battery holder, batteries, lanyard, sticker, and neat presentation box, in exchange for a donation. They were so popular that they were soon sold out by the conference’s end.

The most striking aspect about this badge has to be the bi-color custom solder mask design. Combined with the simplicity of the circuit, it makes a neat little SAO, great for randomly adding blinky scallions to other Defcon badges.

Having had a personal input in the preparation and manufacture of these boards, I thought it would be neat to share some of the challenges Seeess and Seeed Fusion faced in the production of these boards. Particularly, regarding the vibrant design for the PCB nerds out there. We also have an assembly video to top things off.

No simple feat

Prior to coming to Seeed, Seeess had tried other fab houses for the previous badge runs. This time, fully aware of Defcon’s high standards, Seeess decided to fork out the cost and effort for an awesome badge design. With help from a designer, Seeess had the Gerber files ready for his three tone boards. But after enquiring at various fabs, the scale of his proposal quickly sunk in.

Basically, you are not going to be able to achieve any kind of custom solder mask design with the cheaper quickturn factories – the kind that panelizes orders from different customers together to save on materials and handling steps. In the typical PCB production process, everything is processed together until they are milled apart – one of the final production steps. That means everything is handled on a panel-by-panel basis. So if one customer’s design needs a special color, then all the boards on the panel will have that color. If one needs extra solder mask coatings, then the whole panel goes along for the ride.

Essentially, they have no capacity to produce them and are simply not interested in the extra effort. It’s just a color dammit.

If they suddenly switch to a special solder mask color, then they need to clean the silkscreens or set-up a new station, especially for this order.

But as I’m sure you know, solder mask resist now comes readily available in a wide multitude of colors sometimes at the same cost as the standard green. Many quickturn factories can offer the relatively standard rainbow of green, blue, red, yellow, black and white nowadays, and it’s increasingly more common to find other crazy colors like orange, baby blue and even clear solder mask. Colorful solder mask oils are no longer a simple gimmick, they’re the main aesthetic, giving the boards character and individuality and the top wowers are willing to go the extra mile for that unique look.

That is where the traditional “Premium” production facilities come in. The keyword here is tailored. In such production lines, every order is dealt with individually and production processes are adjusted according to the specific requirements of the design, whether it’s a special combination of parameters, laminate stack-up, intricate copper pattern or something else. Of course, this comes at considerable extra expense – even for relatively simple designs, so expect to pay up. For this board though, I’m sure Seeess would agree that it was definitely worth it. The closest alternative would be to have darkish purple solder mask and silvery HASL surface finish for the flesh? It’s not the same.

There are two main challenges with boards like the Tor badge. We don’t just have a custom solder mask color, we have an extra solder mask layer. Making it doubly expensive even by Premium standards.

For a custom color, it’s a case of just mixing two different colors together, but the colors can change as they go through the developing and curing processes making it difficult to predict the final outcome. Two batches made using the same factory can have vastly different results. Also, the mixing is an art itself, you have to consider the properties of the different colors. Yellow, for example, is a very weak color and more translucent than others.

But wait, there’s more. Custom solder mask is one thing, having multiple layers is another. Each color must go through a separate round of application, developing, curing and cleaning which, as additional manufacturing steps, literally pokes holes in the wallet and extends the lead time. Not to mention, the additional baking steps can further affect the colors of the previous layers and even the integrity of the solder mask. A little too long in the oven runs the risk of peeling and blistering and so extra boards may need to be made to compensate for the high wastage rate.

For these boards, Seeess initially came knocking with the Gerber files of two silkscreen layers for the purple ‘skin’ and the black outline, and a white solder mask layer. We suggested going for purple solder mask instead due to the points mentioned before so the files had to be modified. Those of you familiar with the Gerber format will know that all Gerber layers are positive except for the solder mask layers, which are negative. That means filled areas correspond to a lack of solder mask in that area. It’s important to get this right with any PCB design or the results could be disastrous*.

It looks wrong, but it’s right

*Communication is key. The CAM engineers should be able to make the modifications for you but you must ensure that they understand the desired result.

So, after confirming the Gerber data and some final tweaks and checks, the order was ready to go.

Et viola!

Packing Onions

All of those production complexities with the PCBs make the assembly sound easy. And for this particular board, consisting of a total of 15 components each, including 1 standard through-hole SAO connector, there’s nothing complex about it. Having all the SMT components on one side also simplifies things significantly.

We’ll let the assembly video say the rest:

After automated assembly, it was just a case of soldering the SAO connector on the back of the boards and that was it.

Complete with the new SAO standard connector.

Difficulties encountered: Getting the side and orientation of the SAO connector right due to lack of silkscreen indications. Seeess made sure to communicate this to us from the beginning so it was no problem.

Scan the QR code on the badge or click the link for the Github repository and an honest review of the Seeed Fusion PCB Assembly service from Seeess.

Boards in action:

We’re grateful to Seeess for making the onion boards for us. It was our first time as a vendor and our first official badges. They were available by donation, and we sold out before the event was over. The Tor onion represents the layers of encryption our software provides, so it was a perfect fit for the con.

We believe everyone should be able to explore the internet with privacy.

We are the Tor Project, a 501(c)3 US nonprofit. We advance human rights and defend your privacy online through free software and open networks.

The Tor Project

Interested in going the extra mile to stand out from the crowd? Get in touch or place a quotation request directly on the Seeed Fusion Advanced PCB form.

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August 2019