Design For Manufacturing
A team of more than 50 engineers and developers are working around the clock on the other side of world to help us build the Light Phone. The team consists of mechanical engineers, electrical engineers, industrial designers, tooling specialists, radio frequency engineers, program managers and software developers. This is just to review, test, and source the parts for the first build of the phone. They are consumer electronic professionals.
Working on the DFM (Design For Manufacturing) can feel like a puzzle especially with our form factor because we’re so limited on space that every move requires moving lots of other things too.
GPS
The Light Phone is just a phone. We intentionally didn’t include Wifi, Bluetooth, GPS, an NFC chip, camera or any of the many other things you might find in most smartphones today. However, as we dove deeper into designing the phone and checking off all federal and carrier regulations we realized that GPS is a mandatory requirement for mobile phones in many countries. The GPS will not be activated on the Light Phone unless an emergency number (911) is dialed. In the future, we can allow a parent to access the GPS in the case that give the Light Phone to their child.
Radio Frequency and SAR Levels
Radio Frequency and SAR (Specific Absorption Rate) is something we take very seriously. It is essentially the amount of radiation that our phone emits. We spent a lot of time troubleshooting and finding solutions for ways to optimize the levels for the Light Phone. SAR is a measure of the rate of radio frequency energy absorption by the body from the source measured. All cell phones must meet the FCC’s RF exposure standard, which is set at a level well below that at which laboratory testing indicates, and medical and biological experts generally agree, that adverse health effects could occur.
SAR testing uses standardized models of the human head and body that are filled with liquids that simulate the RF absorption characteristics of different human tissues. SAR level is directly related to the distance between cellphone and human body, and the test is extremely sensitive, to the point that even 0.01mm makes a difference.
Our team spent weeks working on it trying to find a way to move the main antenna around to the back of the phone, add metal shields, and fine tune the signals in order to optimize its SAR level. After multiple layouts and tests we found the optimal location within our form factor. This was also time consuming because we are very cautious about our use of funds and these tests are quite expensive.
Microphone & Micro USB Position
Moving the antenna interfered with where we imagined the USB module and microphone originally. Since the main antenna was the highest priority (SAR value), we made the decision to move the receiver holes and USB module to the lower right corner instead of keeping them centered.
The Display
When you turn on the Light Phone, the interface lights up through the casing of the phone. It consists of the display and the keypad. The keypad is the touch module where all of the buttons are located. The keypad is fixed like a stencil. The display, located at the top, however, needs to be able to change to tell us different information like the time, who is calling, the remaining battery, or signal strength.
Our plan was to build the display area with a matrix of LED lights so that we can control patterns. However after researching and surveying vendors it appears that even the smallest LED lights are way too large for our design.
The team felt strong about an OLED module they found, and in testing it worked quite well. It offers flexibility in displaying a variety of characters as well as sizes. The tradeoff is that the OLED module itself is slightly thicker than the LED matrix and we would need to make room somehow.
Receiver Holes
We designed the receiver holes as three small circular holes at the top of the phone where the speaker would sit close to your ear while talking on the phone. The microphone located on the thin bottom edge of the phone has identical holes near where your mouth would be speaking towards the phone. The original diameter of these holes was 0.8mm.
Our manufacturer worried that the opening ratio, a mathematical way to predict the sound quality out of a given shape, was too small. The team shared some of the common designs among the local handset manufacturer that we could re consider using to optimize the Light Phone.
Although these designs were effective, visually it was unacceptable for the Light Phone. We needed to make sure the sound through the opening would not be distorted and would be loud enough to hear. By increasing the diameter of our original holes by 0.4mm, we were able to find a balance of design and function.
Plastic Casing
The Light Phone was designed with a very thin outer plastic casing and a metal interior support frame. We anticipated the challenges in making the plastic thin, as molding plastic really is an art in itself. Plastics are usually produced from a molding machine with steel tools cut specifically for a unique design. Things like molding temperature, pressure, the gate design, various types of molding machines, location of water lines, and other factors are key to producing the proper mold for a plastic part. Making a very thin piece requires using high molding pressure and temperature to ensure a good flow throughout the mold, however there is also an increased possibility of creating unwanted marks or deformation.
Simulation was able to help guide our decisions. These graphics below represent the problems we could predict happening with our thin casing, so we were able to iterate before kicking off our first production round.
Typeface Design
We originally thought when we first started designing the Light Phone in 2014 of using a fixed design LED screen like what you have seen for years on devices like digital clocks. We imagined using a screen like this that was 10 characters wide, a phone number’s width.
The problem with screens like this was that if we wanted to put names or the time up, depending on whether there was odd or even number of characters, it would always be off center. We also struggled to find one as small as we needed. This is one of the main reasons for going with OLED.
The display is 96 pixels wide and 16 pixels tall, which means that each letter needed to be about 8 pixels wide and 16 pixels tall, a 2:1 vertical ratio.
The design of these letters and use of this exact screen are still a work in progress although we have been testing a lot with paper to get the scale and letters looking nice. Once it becomes light shining through the casing it can be a different story. This is the latest version of our typeface for the phone. We will share the progress of the real screen as we continue to go through this first production.
