This is first of two final project logs to conclude this project. This log deals with redesign, assembly and testing of DIYTIL305 boards. Finished boards are shown later in the log. Second log will describe problems and things I learned working on this project.
After making first version of DIYTIL305 (previous project log) I needed easy way to test those boards after assembly. Solution was "TIL305 Test board". Since I needed to order PCBs for different projects from fab house, I designed this test board to make life easier. Image shows original TIL305 displays being tested.
Then I redesigned DIYTIL305 PCB to make assembly process easier (bigger led pads, adjusted solder paste expansion) and tweaked dimensions to mimic the original.
Next up was assembly itself. First I made one display with red leds to see if changes to the new design are good. Success! First board passed the test with all leds soldered correctly. That meant I could move to other boards(colour variations).
0201 leds are only available in red, green, white, blue, orange and yellow colours. I used all colours except yellow because it is not that much different from orange. White leds were hardest to place because they don't have transparent case, so they can't be visually inspected for correct orientation.
Before proceeding to glueing displays together I cleaned PCBs of dust and flux residues using isopropyl alcohol and kimwipes.
Polycarbonate filters(CR-39) were used as display covers. They were glued using 3M VHB 4910 double sided tape. Transparent, acrylic foam tapes are used where clear attachment of two materials is needed and therefore are ideal for this application.
Glueing display covers was straightforward, but since I didn't have access to laser cutter I cut them by hand using box cutting knife(scoring and snap method). They aren't the prettiest, but for a few prototypes they are good enough.
I made six displays in total. Now I just need project to use them on. Any suggestions?
This week I assembled few DIYTIL305 modules. Main problems were: Solder paste that wouldn't go through stencil, leds sticking to tweezers and not being aligned with footprint after reflow process.
First problem was solved by getting finer grain solder paste (in future led footprint will be adjusted). Solution for second problem was to clean tweezers with rubbing alcohol multiple times during assembly process and re-heating leds with hot air gun with addition of flux so they align with footprint (some leds are still misaligned).
Afterwards I did some comparison between DIYTIL305 with red transparent acrylic and original TIL305 (last two pictures). In those pictures DIYTIL305 consumed 1.27mA and TIL305 15.78mA.
DIYTIL305 is made out of three main parts:
According to datasheet dots on TIL305 are arranged on 0.05"(1.27mm) grid. With that information I can now measure the size of a single dot. On the picture below each increment of scale represents 0.1 mm. It means that single dot is 0.4x04mm. I thought incorrectly that they were 0.6x0.6 (drawing from datasheet is more symbolic than actual representation of the part).
For my version of TIL305 I will use 0201 leds(0.65x0.35mm) rotated by 45° on 1.27mm grid.
Display showed on pictures below has marking "KOREA 8418".
While researching TIL305 I discovered TIL302. It shares same package as TIL305 but is configured as seven segment, unlike TIL305 which is 5x7 matrix. I had to get one so here are some pictures: