On Sat, 27 Jun 2009 10:08:29 +0100, Raveninghorde
raveninghorde@invalid wrote:

On Fri, 26 Jun 2009 20:10:27 -0400, legg wrote:

On Fri, 26 Jun 2009 09:56:13 +0100, Raveninghorde
raveninghorde@invalid wrote:

On Thu, 25 Jun 2009 22:28:13 -0400, legg wrote:

On Thu, 25 Jun 2009 11:40:39 +0100, Raveninghorde
raveninghorde@invalid wrote:


Here is my new light bulb, minus reflector.

168 112 lumen leds in 14 strings.

The main problem is the aluminium of the pcb is not earthed causing
problems with current control presumably due to much higher stray
capacitance than we had on FR4. Just got to find a neat way of
earthing it.

Why the 'S' pattern, and why copper-free areas (if thermals are an
issue)?

Must be a really hefty pre-heat for reflow. Are the leds compatible to
this fab step, at all?

RL

The S pattern is just to keep the orientation the same for all the
leds.

A 90 degree rotation would afford the same feature, without involving
the dissipating areas.

The copper free areas are due to the design of the reflector which
bolts down on the board.

reflector? not a diffusor?

Good luck in reflow.

RL

Our reflow is not up to this job and will be replaced if this goes
into production. I'll replace it anyway as soon as I get sight of the
right second hand machine.

I had the boards assembled by the company who made the blank pcbs.
They specialise in this stuff. They did a great job, 48 hours from
gerbers to assembled boards.

It's not often true, that what you don't see, can't hurt you. I
suggest that you inquire as to the equipment and techniques that were
used successfully.

RL