“Will exposing areas of a PCB board that are not covered by an adhesive or conformal coating to UV curing energy damage the board in anyway?”
Any frequency of energy that gets impinged onto a substrate has two options: it can get reflected, in which case it is harmless, or it can get absorbed, in which case it will turn into heat. Some light-curing equipment, like the Dymax BlueWave® spot lamps, have an intensity adjustment feature which allows for the ability to reduce unneeded energy. Adjusting the intensity reduces any excess energy that may turn into heat and damage temperature-sensitive substrates.
Adhesives, Curing Equipment, Electronic
“Dymax curing equipment can be outfitted with several different types of bulbs. How do I choose the right bulb for my application?”
Metal halide bulbs (lamps) come standard in Dymax UV light-curing systems to match the cure chemistry of most high-performance UV-curable acrylate and cationic epoxy adhesives and coatings. Other bulbs offered include Mercury bulbs and visible indium bulbs. For curing UV inks and some (usually very thin layer) UV coatings, Mercury bulbs provide better surface cures faster. For applications where visible light is predominantly required for curing bonds between UV-blocking plastics, visible indium or “V” bulbs are best. The best approach to selecting a bulb is to speak with a Dymax Application Engineer. With a little information about your application, an Application Engineer will be able to select the most efficient bulb for your application.
“About ten years ago I worked for a start-up electronics manufacturer. In the lab we had a machine that dispensed UV-curable epoxy and had a UV spot lamp attached to the dispenser. It was all controlled by a foot switch for both adhesive dispensing and light control. We used it for numerous tasks such as bonding modification wires to the board as well as bonding components to the board. Does DYMAX offer anything like this or do you know of anyone who does?”
This unit was called the DYMAX PC-3D, with a dispensing system on one side, and a UV-curing system on the other. While there might be a few available units floating around eBay, these units are not manufactured anymore. At this point, they are stand-alone units. DYMAX can offer the individual lamps and air/pressure dispensing systems separately, but we do not have a combination unit like the PC-3D available anymore. I am not aware of anyone on the market making a unit like this currently. Sorry!
"I have an application where we would like to cover the edge of a silicon die (that has been first tacked in place with epoxy that has been cured to a Valox/PBT base) with an uncured epoxy. Then add additional epoxy to a second bond location that ultimately bonds the Valox base to a Valox cover that has a slight press fit, covering the silicon die. After the press fit assembly, I would like to light or UV cure through the cover plate, causing both applications to cure. By both applications I am referring the bond line between the Valox cover plate & Valox base as well as the edge coating around the periphery of the silicon die, bonding it to the Valox base.
Are there any polymers that can transmit UV or light sufficiently to allow these types of cures? Is there a special light source required? Can the polymer be anything other then clear? Lastly, is there a medical-grade polymer that can achieve this?"
There are a couple of ways to handle this application.
There are a number of polymers that can be used for a cover plate that will let light through, whether UV or visible light. One way is to use a tinted plastic like polycarbonate or acrylic. Tinting the plastic with a dark blue dye will create the "illusion" of being opaque, but will let the proper wavelengths through the plastic to allow it to cure. Finding the right balance of dye will be critical. One way to judge the impact of the dye in the plastic, or the transmission through the plastic, is to measure the intensity of light coming through the plastic from the light source. You can calculate a % loss of transmission through the plastic in both the UV and visible regions. Most adhesives want to see a minimum of 200 mW/cm2, and some of the light sources on the market are emitting light of 20,000 mW/cm2. Even if the plastic blocks off 90% UV light, and 70% visible light, this might be enough to allow it to cure. If the plastic compounder uses a pigment to augment the tint, make sure the level of pigment is low, and they use a white pigment like Titanium Dioxide. A good field test – if you hold the plastic up to the light and can see a shadow as you wave your hand behind it – you might have enough light coming through to cure the adhesives. Stay away from yellow-orange-red colors. Whites, blues, and greens are better. There are a number of medical grade adhesives that can be used for this application, and various curing lamps. I might recommend contacting DYMAX Application Engineering to arrange for some free samples and to discuss our Trial Rental/Lease Equipment program. www.dymax.com.