The LED Artist - blog » PCB

A Gatcha with PCB Panel

The LED Artist — Sun, 20 Jan 2019 03:34:06 +0000

Recently I started panelizing my own PCB designs to speed up SMT production.

I used to ask PCB fab house to panelize my designs, but Altium Designer has a board array feature that makes panelization very simple. Also PCBWay, my go-to PCB fab accepts panelized gerbers the same way single board designs. So I have become comfortable panelizing my own designs.

This PCB was for JT Filament – the through hole design has been available as kits, but I started offering pre-assembled version as well, so I wanted to produce SMT version for that.

The panels and the stencil were produced in two days and delivered via DHL Total turnaround was only 5 days. This is crazy fast. (No rush fees paid. Note that it’s not always so quick, but sometimes you get lucky.)

Panels and stencil delivered. Oh and the holiday gift.

I ran the first batch of 4 panels as a test. Stenciling, pick & place, and reflow went without a hitch. I was very happy.

Stencil and the PCB Panels

Using low temperature paste for reflow – to protect the filament LEDs.

Assembled and reflowed panels

After testing each circuit on the panels, I went on to break them apart… That’s when it hit me – those V-scores are not snapping like I expected. After trying out some forceful ways to break the panels and only getting two boards successfully separated, I started to panic.

I talked to the support person at PCBWay and realized that my panelization had two problems;

The boards were too close together (the support between the V-score lines needed wider).
The inner cutouts left only thin strips next to the V-score line. This part can break or twisted during the depaneling.

#2 seemed to be the major issue, and since I can’t change the board design itself, I had to change the panelization. I decided to use tab-route instead of V-scoring. Which means I will have to file away the mouse bite residue after depanelization. Oh well…

I am now waiting for the delivery of the new panels (while keeping my fingers crossed). Will post the result soon.

Here’s how I do my SMD PCB assembly

The LED Artist — Wed, 09 Jan 2019 04:22:34 +0000

I design a lot of PCBs, and assemble most of them myself. Small quantity PCB fabrication services have become so popular and abundant, I take full advantage of them.

Recently I use PCBWay a lot. Their pricing is close to the lowest (sometimes is the lowest), but the quality is still quite good. My favorite part of their service is that they offer different solder mask colors without extra charge. I don’t like green PCBs so this is a big plus!

For small boards for prototypes, batch based PCB service such as OSHPark still wins, as the shipping cost is much lower than from China. I use OSHPark for boards up to 2 sq inches, and PCBWay for larger.

Oh and PCBWay (and some other Chinese PCB fabs) offer stainless stencil for a very reasonable price. I can usually add one for $10 and it is very nice to receive PCBs and the stencil together.

Here are the photos from my typical PCB assembly using the nice stencil.

Step 1: Gather All Materials

Clear your work area and gather all components, material, and tools. Preparing the organized BOM printed helps to reduce errors.

Step 2: Frame the PCB and align the stencil

I use squares made of fiberglass to secure the PCB to the desk. Then overlay and align the stencil on top, and secure it with a piece of masking tape.

Compared to Polyamide (orange plastic film) stencils, stainless stencils are easier to align to the PCB. The pads kind of “snap” into place.

Step 3: Squeegee time

Now it’s time to spread some solder paste onto the PCB. Use plenty of paste and pull the squeegee at a steady speed.

Here the stainless stencil really shines, as the paste spread very smoothly without effort.

(Ok, I could’ve done a better job, but…)

Step 4: Ready to Pick & Place

Now the PCB has solder paste beautifully printed on, I’d get busy placing components.

Step 5: Ready to Reflow

Here the boards have all the components placed and ready to reflow. Sorry I forgot to take photos during the pick & place process.

I use a small reflow oven to reflow PCBs.

Rustybolt.info mention of JT Blinker

The LED Artist — Sat, 15 Sep 2012 00:00:13 +0000

Mr. Watson of Rustybolt.info blog wrote about the LED blinker circuit using Joule Thief. I’ve sent him a PCB of my prototype, named JT Blinker – multivibrator and Joule Thief combined to blink LEDs with one 1.5V battery.

He had designed a similar circuit years ago, and has some insights about this type of circuits…

> read the article at Rustybolt

Some Old Works of Mine

The LED Artist — Fri, 03 Aug 2012 05:10:15 +0000

I was doing some clean up and found some old works from years ago…

The one above is a multi-purpose PIC pad using PIC16F627. This was an exercise of multiplexing 7 segment LEDs and button matrix using the same set of I/O pins. I wrote code to make it work as a timer and organ (more like a beeper with notes). 2 AA battery holder was connected to it, but obviously lost.

This was done in April of 2003. Before Arduino and all that good stuff was available. Home etched and hand drilled PCB. What’s amazing to me now is that I designed the PCB in Adobe Illustrator! I did not have a CAD software.

> PCB Layout

Next up is my very first LED project using PIC microcontroller, which was done right around the same time as the pad above.

> Schematic
> PCB Layout

I used four microcontrollers on this one. three controlling LEDs, and another one controlling them. The center one is the “master”, sending command to the other controllers to orchestrate the animation. The three “slaves” are just controlling the LEDs as they are commanded. The setup seems more complicated than my recent projects, but back then I was literally applying “divide and conquer” method to the circuit design.
When I first envisioned this one, I had no knowledge of microcontroller. I had some electronics experience and knew how to use logic ICs, however it quickly became clear that what I wanted to do was too complicated to accomplish with logic ICs. So that prompted me to look around, which led me to BASIC Stamp. BASIC Stamp, for those who never hard of it, it’s kind of like a pre-Arduino. You can write the code in BASIC language and upload it to the chip over serial cable. It was easy to use, but the processor was very slow.
Faced by the limitation I decided to learn to code PIC microcontroller directly. It took me a while to get into, but I managed.

I made a revision of the same circuit, multiplying the number of LEDs by using a complementary drive approach. (July 2003)

> Schematic
> PCB Layout

After this prototype, I decided to move on up to manufactured PCB. Found a free PCB design software (called Osmond PCB – which I still use), and start having my PCB made by a factory. This enabled me to design with fine traces and more precision.

Wave JT – Kit and PCB

The LED Artist — Sat, 28 Jul 2012 02:00:15 +0000

Wave JT is a tiny LED sequencer or “Larson Scanner” on steroid. It has over 16 sequence patterns, and speed can be adjusted by double/triple tapping the button. It’s the most versatile LED chaser.

Unlike other LED chasers, Wave JT controls each LED in smooth 7 bit (128 levels) brightness levels. The brightness curve is gamma-corrected like Aurora series, so the fades are visually pleasing.

Not only Wave JT versatile, it’s also energy efficient. Wave JT runs on a single AA battery, and the battery lasts for days!

> See more pictures and video

Please view technical details and assembly instructions at instructables.

Wave JT is made with 100% through hole parts. No surface mount parts!

Kit Contents
8x 3mm or 5mm Super Bright LED of your choice
1x 4.7k ohm (R1)
1x 100k ohm (R2)
8x 39 ohm (R3-10)
1x 10pF Ceramic Capacitor (C1)
1x 0.1uF Ceramic Capacitor (C3)
1x 33uF 10V Electrolytic Capacitor (C2)
1x 47-100uH Axial Inductor (L1)
1x Schottky Diode (D1)
1x 5.1V 500mW Zener Diode (D2)
2x MPS2222A or equivalent NPN BJT (Q1-2)
1x PIC16F1823 or PIC16F1824
1x Tactile Switch (SW1)
2x Battery Clips

Note: As of Oct. 1, 2012, all Wave JT kits are shipping with preprogrammed PIC. You do not need a PIC programmer to assemble Wave JT kits!

*** Purchase Here ***

Colour Night Joule Thief kit

The LED Artist — Fri, 24 Feb 2012 19:47:05 +0000

Colour(Color) Night Joule Thief kit and PCB are available. Please use the buttons below to purchase.

Detailed information and building instructions are here: http://www.instructables.com/id/Colour-Changing-Night-Joule-Thief/

*** Purchase Here ***

Night Joule Thief – LED Night Light Kit

The LED Artist — Mon, 05 Sep 2011 00:48:00 +0000

Joule Thief circuit is combined with an ambient light sensor – Night Joule Thief is a little night light that keeps going with just one battery for weeks! Two white LEDs light up surprisingly bright.

* This is the original version of Night Joule Thief that uses white LEDs – not to be confused with the new color changing version.

Please view the instructables for technical info and assembly steps.

*** NOTE: The color of the PCB will be green instead of purple shown in some of the pictures. ***

*** Purchase Here ***