How to make sure that SD package is mounted well without the CO clamp. I was using a spring contact made up of BeC and found somehow the contact is not perfect. while using Indium, it has to heat the whole mass of the substrate where we want to mount the sensors to 180 degree which looks diffciult. which method is more reliable. and for connecting wires to sensor leads, ostalloy does not give good joint strength. so how can one solder the wire to sensor lead using a solder within 200 degree Celcius.
Post by Lake Shore Scott C on May 17, 2017 11:02:19 GMT -5
Thanks for your question. The mounting method depends on a few parameters includinig temperature range and ease of removal. Is this to be a permanent mounting? If so, you might consider an epoxy like Stycast 2850. If not permanent, then the question becomes how easy you need it to be to remove the sensor. Soldering requires heating the surface where it's mounted which isn't always ideal, but you can use IMI-7031 varnish. You'll need to use a solvent to dissolve it when you want to remove it. The spring clamp is also a useful way to mount it, although I would also use Apiezon N-grease to fill voids between the sensor and mounting surface. That has the advantage that the grease will harden as temperature drops and help hold it in place while giving a better thermal connection as compared to just a spring clamp. As long as the spring clamp captures the SD package to prevent it from moving, it should be a perfectly good way to mount the sensor.
With regard to the solder question, most of the lower melting point solders aren't as strong as what we've come to expect from 60Sn/40Pb or 63Sn/37Pb. There are a number of solders that can be used. I would probably use indium solder with a melting point of 156.7 degC. It's had a long history of use in cryogenics and should be reliable. A company with a wide selection of solder choices is www.aimsolder.com and they can send you a list of solders in Excel spreadsheet form allowing you to sort by melting point. Good luck and let us know if you have further questions.