Jeremy Rubin's Blog

Engineering Query at King Kredie

Shenzhen Adventure Day 12

Inside the King Kredie Engineering Query room

On Day 9 I mentioned that we had submitted our boards for Engineering Queries, but I didn’t quite explain what those are.

When you’re working with a good manufacturer, they don’t just blindly produce what you tell them, they will go through and verify certain properties of the design to make sure it will come out as expected, or even tell you ways you can save costs that you may not have thought of. This is because:

1. they want your future business
2. they’re just good people
3. they don’t make more money on the more expensive process

3 can happen because a different process may have no different labor cost, but just a material cost which they don’t mark up. This is an important point to keep in mind when working with various manufacturers – they will pass savings on to you if possible!

Flex PCB Factory Tour at King Kredie

Shenzhen Adventure Day 12

While we were doing the Engineering Query at King Kredie, we also got a special bonus tour: Flex PCB Manufacturing.

Flex PCB is kind of the future – as devices get smaller, a thick-old-green PCB is no longer practical unless it is also a structural element. Flex PCB’s, traditionally used more often as a custom connector, can be populated with components as well so are a really cool technique to experiment with.

The process is pretty different from traditional PCB etching.

You start with a big roll of copper foil.

Punch out a pattern using a big press.

The die looks like this:

Then you laminate it. The laminate sheet has also been punch cut appropriately.

An iron is used to bond the plastic laminate to the copper/backing laminate.

Then you (optionally) silkscreen print on

Alignment is not critical here.

Finished product:

This flexpcb has a stiff copper trace inside of it as well for rigidity on that axis

Later on, these will need to be cut out/depanelized.

Tea Ceremony

Shenzhen Adventure Day 11

The printing press guys were really the best – so good, they get three posts for one day!

Following our visit, they taught us how to do – and appreciate – the traditional tea ceremony.

To make the tea ceremony, first you use hot water in a little basin to wash out all of the tea cups. Then, you fill the teapot with tealeaves, and use the basin (with fresh water) to pour hot water over the leaves. You stir by gently shaking the tea for 30 seconds, and then pour out the water. The first wash is thrown out traditionally to make sure the leaves are clean. Then, you repeat and let steep for a few minutes. You drink all the tea, and then repeat over multiple washes of the tea.

The tea they were using was incredibly good; probably the best I’ve ever had. When we asked where it came from, they told us their friend grew it!

A parting gift

The week we were set to leave Shenzhen, the guys from the printing press sent us a big box of the tea we made the ceremony with. I’ve shared my stash of the tea with friends and family, sharing my stories from Shenzhen, especially the generosity of everyone who made us so welcome there!

Seaside Lunch and Opium War Museum

Shenzhen Adventure Day 11

With the guys from the printing press we got lunch in the middle of our tour.

We went to this lovely restuarant by the sea that had really fantastic seafood.

The sea is that color from sediment

After lunch, we went to Shenzhen’s Opium war musuem and saw some of the exhibits. It was really interesting to see the Chinese perspective on this era, and the museum itself was interesting architecturally.

The MIT Crew entering the museum

Printing Press Tour

Shenzhen Adventure Day 11

Today we got to see a printing press. Printing presses are pretty cool; they’re a pretty old technology which one might argue was the driving force behind the renaissance.

Printing

Printing presses are fast. If you’re looking to get something made at one of these factories, you need to order at least something like 10,000 copies because it prints that many in about the time they can turn the machine on and off.

Gold Leafing

One of the coolest processes we got to see at the factory was how they gold-leaf page edges.

Basically, they sand down the edges of a block of paper to be super smooth.

And then they press a piece of foil onto it.

The result is very shiny!

Paper Cutter

Imagine cutting a piece of paper. Now two pieces. Four? 16? 32? At a certain point, the paper becomes too thick to easily cut.

Now imagine you aren’t just trying to cut it, but you’re try to make a perfect edge, uniformly.

At a printing press, they cut thousands of sheets simultaneously. That requires a really sharp knife, a lot of pressure, and a highly attentive worker.

At the factory, pages are typically cut twice. The first time is to cut to the general size of the job and the second time is done as a trim on the finished product to remove the edges.

Binding

These big rotary machines are used to bind pages

Special Requests

Printing presses – or at least this very awesome one – can accommodate a lot of special requests.

Here are a few examples of special processes

Adding a bookmark

Plastic window