|Ask the Experts|
July 21, 2020
Production Floor Temperature and Humidity Loggers
Early this month we had a customer audit. One of the findings regards the environment measurements in our assembly area. They noted that we only have one temperature/humidity logger and it was considered inadequate given the size of our production floor.
Isn't one temp/humidity logger per facility adequate? If we add additional temp/humidity loggers, where should we place them? Near machines, near the center of production area, in the four corners?
|Expert Panel Responses|
Wouldn't it make sense to put temp/humidity monitors in critical locations, such as board and component storage areas, near the solder paste stencil printer, near the functional and in circuit test areas, and any where assemblies are staged that would sit for more than a few hours.
President/Senior Technical Consultant
Temperature and humidity can effect ESD, MSD, screen printing, working time, and shelf life. If you don't measure/monitor all the multiple areas, you'll never be able to prove you don't need to.
M.O.L.E. Line Product Manager
Electronic Controls Design, Inc. (ECD)
Whether one logger is enough is entirely dependent on the facility. In facilities where airflow into/out of the facility is tightly controlled, and the facility is under slight "positive pressure" with more make-up air than exhaust, one logger might in fact be enough. In many facilities, especially older ones, we don't have this luxury. How many loggers we need, and where we place them will depend on a number of variables.
Some of these are:
Correlate your temperature and humidity data with the outside temperature and dew point. The outside dew point is an incredibly important factor, and is the one variable that drives out-of-control conditions on the shop floor more often than any other, in my experience.Once you know where your "sensitive spots" are, you can add loggers to keep track of them. On most moderate-sized production floors, I don't see a big benefit to more than three loggers, in most cases.
One should not challenge an auditor, however it would be fair to ask, what standard indicates that more than one temperature/humidity instrument is required. IPC standards (J-Std 001) recommend you control the temperature and humidity, but they do not tell you how.
However, rule of thumb can apply here. One question to ask yourself: How many HVAC system control thermostats are in the same area/facility? It would be fair to suggest that you should have the same number of temperature/humidity measurement instruments in that same area/facility. Another rule of thumb is one temperature/humidity instrument per 10,000 square feet of floor space.
As for where to place them, this is simple: where people and product spend the most amount of time. The whole point of measuring the temperature and humidity is to document that people and product are NOT being subjected to extremes. So place instruments where the action is: on the line, in or near the machines, etc.
Senior Project Engineer
Electronic Controls Design Inc
First & foremost..."your customer audit" They are making the request. Customers are hard to come by. Monitors are relatively inexpensive.
You do not indicate the size of your facility so an accurate answer is difficult. A monitor at the center of your facility is ideal but it will not provide accuracy of readings at the far corner, say near your reflow line or your washing system. Humidity will generally be different in various areas of your facility.
The question itself raises these questions... are you controlling humidity currently?
Where are you located? A high humidity area... Florida? A low humidity area... Arizona?
There are wireless units on the market now that can mo niter locations & report back to one central PC. This provides facility wide reading with automated recording of the factors required.
Humidity and temperature monitored areas are areas where these parameters can possibly impact the process yields and or quality.
Some areas that are normally monitored are:
Senior Market Development Engineer
The answer is dependent on the uniformity of the temperature and humidity within the room or on the factory floor. Large areas are subject to variations in temperature if the air handlers are not positioned properly or correctly balanced. A common mistake is locating temperature/humidity monitors within the near draft path of an air conditioner vent. Ideally, before stationing any temperature/humidity monitors, the room will be mapped especially for temperature uniformity.
Influences of operating equipment,the number of people present, outside environment, wind conditions, opening and closing doors, consistency of air conditioner output, exhaust stack vent motors on and off, among other factors, can all impart changes to the environment.
Even after such mapping and impact studies, I always encourage deployment of multiple recording temperature/humidity monitors; one in the center and at least a couple at extreme opposite corners or a large room or factory floor. Frequent and routine monitoring of the temperature/humidity graphs is a must to understand environmental impact on materials and ensuing quality.
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