2012

Controlling Heat Curing Adhesive Processes Using Infrared Spot Curing

IRphotonics application engineers have performed work that validates that the cure resulting from a focused photonic curing system led to complete cures. A particular customer needed to move their component to another station without fixturing the assembly and asked for a way to accelerate the cure. The first step was to establish a baseline for the uncured adhesive and the DSC scan for the thermal curing epoxy used by the customer was taken and is shown in Fig. 3. This particular epoxy is designed to cure at 60 °C for 20 minutes in a convection oven according to the glue manufacturer’s data sheet. During the initial phases of evaluation, the iCure was able to develop full cures using 2W for 60 seconds as shown by the DSC scan in Fig. 4. This is a 20X increase in cure speed for this particular adhesive and is representative of what can happen with quickly setting thermal glues. Application Engineering is an important part of optimizing cure profiles and this demonstrates that the contribution of technical people experienced with photonic thermal curing is critical to a successful application. It is important to keep in mind that the results are valid only for the set conditions as actual manufacturing conditions, substrate conditions, and adhesive quantity will impact the speed of cure, the time to reach cure temperatures, and the resultant degree of cure.

As previously mentioned, the challenge of using thermally cured adhesives in medical device applications is that the opaqueness of substrates that requires these glues makes it difficult to determine their degree of cure and therefore forces manufacturers to be very cautious and to spend excessive time and energy to assure the end user of a full cure. However, through field experiences and the application of laboratory testing methods, it is possible to create a curing profile that optimizes the cure of the adhesive in a customer assembly. Making the cure station a vital part of the work cell rather than an offline process optimizes the control of quality for medical devices, enhances their traceability, and maximizes the versatility of manufacturing operations without increasing floor space. It also gives design engineers more freedom in designing in bonded joints using thermally cured adhesives.

Since this curing system gives a strategic advantage to the end user, most of the existing applications developed with IRphotonics are covered under non-disclosure agreements. However, generic uses of the technology have been done with the bonding of metal sleeve to metal, glass, or plastic inserts and vice versa. Spot thermal curing or spot tacking of miniature wires, leads, and contacts has also been successfully performed. Other end users have used the power of photonic energy in the iCure to reflow micro dots of solder paste. There are some other generic uses of iCure technology for the gelling or curing of potted adhesive joints to minimize the cure time in the final stages of assembly. Finally, one of the most effective uses of focused spot heat comes from end users who have done controlled heating and curing of assemblies without affecting adjacent thermally sensitive components.

In essence, the iCure Spot Curing technology opens up the versatility of medical device design and manufacturing without the limits of alternate mechanical, ultrasonic, and laser processes and without the limits of transparency required of ultraviolet-visible radiation curing systems.

This technology was done by IRphotonics, Hamden, CT. For more information, visit http://info.hotims.com/40429-168 or contact 1-877-340-6982 and ask to speak to an Applications Engineer.