In my last post, I talked about the types of solder you could find in implantable medical devices, specifically cardiac pacemakers. Pure goldpreforms are generally used as the solder material in the pacemaker assembly due to theirhigh purity, inertness, biocompatibility, high resistance to corrosion, and ability to provide an excellent hermetic seal in the device. However, this is only the second of three main application segments for medical devices (I talked about wearable medical devices here), and we have finally arrived to the final part: industrial medical devices. Magnetic Resonance Imaging (MRI) machines are just one of the plethora of industrial medical devices that have become common use in the medical field today for disease detection, diagnosis, and treatment monitoring.
20 世纪 70 年代，雷蒙德-达马迪安（Raymond Damadian）发明了第一台临床核磁共振成像仪。随着随后几十年技术的长足进步，与20世纪的许多医疗设备一样，核磁共振成像仪如今已广泛应用于医学领域。核磁共振成像利用强力磁铁在患者周围产生一个强磁场，然后同时发送射频（RF）波来生成图像。如果您曾经做过核磁共振成像，您可能会注意到在检查过程中通常会发出巨大的敲击声和咔嗒声，为了让患者更舒适，通常会提供耳机。咔哒和咔哒声就是振荡射频电流的声音。
Less exciting, MRI machines tend to use a combination of solders I have already discussedin parts two and three (SAC305 solder paste and 99.99% gold) in the assembly. So, let’s take a step away from the medical device itself and take a look at the room the machine is in instead. Electric currents that oscillate at radio frequencies have special properties not shared by those of lower frequencies. The energy from RF currents can radiate into space as electromagnetic radiation causing distortion to the magnetic resonance signal itself or interference in nearby medical devices. Therefore, shielding the RF waves generated by the MRI machine, from all angles, is mandatory. Copper is one the metals used for RF shielding because it absorbs radio and other electromagnetic waves, preventing them from escaping the room and potentially causing harm elsewhere. It also easily conforms the shape of the MRI room layout, including any odd angles, multiple corners, etc. and has the added benefit of not requiring much maintenance. To create the RF shield, copper sheeting is overlapped and soldered together to create a uniform RF membrane, and is then placed on supports within the walls, ceiling, and floor of the MRI room. Voila, now the RF waves will be contained within the room!
感谢您参加本期由四部分组成的关于医疗器械中的焊料的系列讲座！
