UV LED PC Board Exposure Build
Using 1watt STAR UV LEDs To Photo Expose a PCB
Each stringer holding the three STAR LEDs is constructed of 1" wide by 1/8" thick aluminum bar was trimmed to 7" in length.
Marking each piece of aluminum for where the STAR LEDs will be positioned. Spacing between the three LEDs is 1 1/4".
To mount the STAR LEDs to the aluminum, several options were reviewed. The most common way is to use two mounting holes per LED and include a screw through the mount, and to dissipate the heat, a thermal compound between the LED and aluminum. If mounting this way, you need to ensure your mounting screws do not short out anything on the LED module.|
Another option which presented itself during the construction was to use a thermal adhesive, one that would provide not only a secure adhesive to mount the STAR LED to the aluminum, but also a heat-transfer medium to transfer the heat away from the STAR LED. A commonly available thermal adhesive is Artic Silver Thermal Adhesive. It is a two part permanent adhesive for thermal joints in minimum bond line applications. It is created with 99.8% pure micronized silver. 62% to 65% silver content by weight, has a wide temperature range (- 40C to >150C) and is formulated to conduct heat and not electricity.
You will not need much compound to hold the STAR LED to the aluminum. Apply equal amounts from the Part A and Part B tubes on to a surface which can be used as a mixing platform. Use a surface which can be wiped clean or disposed of afterwards.
Now go ahead and mix Part A and Part B together. You want to get a good mix to ensure optimum adhesion.
From the mix of Parts A and B, apply enough to cover the bottom of the STAR LED.
Position the STAR LEDs with the adhesive to the aluminum strip. Now would be a good time to align the positive and negative terminals of the LEDs. The negative terminal of one LED should be positioned closest to the positive terminal of the next LED. This will allow you to run a simple, clean wire between each LED when it comes time to connect them together in series.
Each LED should be positioned tightly to the aluminum. Push it into place, and rotate slightly to spread the adhesive under each LED.
After allowing the adhesive to set (in this case, we let it sit overnight), you can go ahead and wire up the LEDs. By aligning the LEDs, you can easily connect them up in series.
To drive the STAR LEDs, we used a 1watt driver. The driver is used to limit the current going to the LEDs, in this case, approximately 285mA. Each support leg has three STAR LEDs on it, connected up in series and run to the output of the 1watt driver. The driver is run from a 12v DC power adapter, with four of the drivers running off of a single 12v 1A power supply.
The assembled frame has four cross pieces each which hold the three STAR LEDs and are 7" in length which attached to a pair of support which are 10" long. The support bars are spaced 1 1/2" apart, with the LEDs being 1 1/4" between each other. The legs selected were liberated from our junk-box and were made up of spacers which measured 3 1/4" long.
Introduction – Design – Create Positive Image – Prepare The Board
Expose The Board – Develop Board – Etching – Thoughts