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Design for Manufacturing | RGB-123

Design for Manufacturing

Giving Back 

Okay, this Kickstarter campaign has been going extremely well and I appreciate everyone’s interest and pledges.  I am trying to be very open with this project and share the steps involved with fulfilling this project.

Planning Ahead 

Prior to this Kickstarter, I have been closely watching other campaigns and the woes they had in order fulfillment.  When the idea came to fill the niche of led matrices I knew that critical to this effort would be the ability to quickly and rapidly come to market.  This involved being able to quickly design, fabricate, and assemble a variety of designs. Using the WS2812 pixels allows for a minimal part count.  Using rapid pcb prototyping from Smart-Prototyping allows for 10 day turn times on pcbs at relatively low cost.  The Quad 4C Pick and Place allows for rapid assembly.  Combining these capabilities has allowed for me to go from concept to production in less than 6 months.  As I prepare for production I wanted to share with you a little bit of this process.

Retired Part

For those of you that are familiar with LED strips the WS2812 (six pin part) is extremely ubiquitous.  However, this part is quickly being phased out and replaced with the WS2812B (4 pin part).  I put a little blog post up about the difference between the two up onwww.rgb-123.com.  In our promo kickstarter video, all of our displays were shown with the WS2812.  However, to go into production, all of the large matrices (88,816,1616) will be made using the WS2812B.  The 1×8 matrices will use the older WS2812s to use up the remaining inventory and speed delivery of the $5 pledge levels.

ISIS 8X8 ISIS 16X16 ISIS 8X16 ISIS FID V Score Description WS2811 vs 2812

Design Updates 

With the WS2812 being retired I am now required to reproduce the mechanical layout of the matrix with this new part.  Luckily, the new 4 pin part has a number of features that make it worth the redesign.  The main benefits are that power and heat transfer are improved.  Additionally, the reduction of the number of pins from 6 to 4 makes the matrices much easier to manufacture.  Mainly this is because there is less likelihood for shorting of pins since they are now more widely spaced and there is a lot more soldermask between the pins.

Having gone through the iterative schematic and pcb layout process in development of the matrices you see in our promo video, the update of the matrix design for the new pixel is relatively simple.

Simple Design

I think one of the best parts of this project is the simple design and format.  It has taken a number of iterations but I think I have nailed the design.  Care was taken to allow for all of the parts to be placed in a repeated fashion.  This makes assembly of the panel much simpler, since all that is required to teach the component placement of the parts in the upper right hand and lower left hand corners.  This is extremely beneficial since this takes only a few minutes on the pick and place versus the programming the placement of each of the 256 pixels (1616) individually.

Below you can see the latest 16×16 matrix layout with the updated WS2812B.  I have added tabs at the top and bottom that are for use with a conveyor on an automated pcb assembly line.  These tabs are separated by applying a V-Score to the pcb.

V Score Description

They allow a pcb to be easily broken apart after the placement and reflow of surface mount parts has occurred.

ISIS 16X16

Looking more closely you can see the global and local fiducials that are used for vision alignment of the pick and place assembly machine.  V-Scoring is used to remove the conveyor tabs after production.Since the spacing of 12.5mm is consistent on all the displays the panel design for the 88 and 816 matrices is nearly identical to the 1616. Specifically, the part placements are exactly the same as the 1616.

ISIS FID

This is important to reduce cost in two main ways:

  • The assembly house only has to program their machines once.  Considering that Non-Recurring Engineering (NRE) fees can run $500 for each design this saves alot of money!
  • A single solder paste stencil  can be used for all of the panels. At $100-$300 per stencil this also saves a quite a bit of money.
Below you can see images of the 816 panel with a single horizontal v-score line.  An 816 panel will produce two 816 matrices.
ISIS 8X16
Here you can see the 88 panel with two v-score lines vertically and horizontally that allow for the production of four 88 matrices.
ISIS 8X8

Pre-Production Boards Submitted

I have submitted these pre-production boards for fabrication and expect to see these boards in about 10 days time.  Assuming the design is good these will be used to produce the early adopter matrices to meet our reward delivery dates.  Any fixes that need to be made will be done and then the BIG order will be placed to produce the final amount of matrices required at the end of our campaign.