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December 13, 2018

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 monitorsin critical locations, such as board and component storage areas, near thesolder paste stencil printer, near the functional and in circuit test areas,and any where assemblies are staged that would sit for more than a fewhours.

Terry Munson
President/Senior Technical Consultant
Mr. Munson, President and Founder of Foresite, has extensive electronics industry experience applying Ion Chromatography analytical techniques to a wide spectrum of manufacturing applications.

Temperature and humidity can effect ESD, MSD, screenprinting, working time, and shelf life. If you don't measure / monitorall the multiple areas, you'll never be able to prove you don't need to.

Mark Waterman
M.O.L.E. Line Product Manager
Electronic Controls Design, Inc. (ECD)
Mark Waterman is a trainer and field engineer with 17 years experience in service and applications specialties. Intimate knowledge of soldering processes and measurement systems. Six sigma and statistical process control generalist.

Whetherone logger is enough is entirely dependent on the facility. In facilities whereairflow into/out of the facility is tightly controlled, and the facility isunder slight "positive pressure" with more make-up air than exhaust, one loggermight in fact be enough. In many facilities, especially older ones, wedon't have this luxury. How many loggers we need, and where we place them willdepend on a number of variables. Some of these are:
  • How much heat and/or humidity is produced by processes on theproduction floor, and where
  • How the make-up air and exhaust are configured
  • Where the main "leaks" are that allow exchange of air withuncontrolled environments, and how big the leaks are
  • The capability of the HVAC system in use
Mypreference is for wireless digital loggers that transmit data to a centralsystem for storage. The data can then be tracked and analyzed. Start with atwo-logger system, with the main logger located near your most critical process(ours is near the SMT assembly area). Move the second logger around to spots thatyou suspect may incur variation; monitor each spot through a few weeks' time,then move to the next spot. Correlate your temperature and humidity data withthe outside temperature and dew point. The outside dew point is an incrediblyimportant factor, and is the one variable that drives out-of-control conditionson the shop floor more often than any other, in my experience.Once you know where your "sensitive spots" are, you can add loggers tokeep track of them. On most moderate-sized production floors, I don't see a bigbenefit to more than three loggers, in most cases.

Fritz Byle
Process Engineer
Fritz's career in electronics manufacturing has included diverse engineering roles including PWB fabrication, thick film print & fire, SMT and wave/selective solder process engineering, and electronics materials development and marketing. Fritz's educational background is in mechanical engineering with an emphasis on materials science. Design of Experiments (DoE) techniques have been an area of independent study. Fritz has published over a dozen papers at various industry conferences.

One should not challenge an auditor, however it would be fair toask, what standard indicates that more than one temperature/humidity instrumentis required. IPC standards (J-Std 001) recommend you control the temperatureand humidity, but they do not tell you how. However, rule of thumb can apply here. One question to askyourself: How many HVAC system control thermostats are in the samearea/facility? It would be fair to suggest that you should have the same numberof temperature/humidity measurement instruments in that same area/facility.Another rule of thumb is one temperature/humidity instrument per 10,000 squarefeet of floor space. As for where to place them, this is simple: where people and productspend the most amount of time. The whole point of measuring the temperature andhumidity is to document that people and product are NOT being subjected toextremes. So place instruments where the action is: on the line, in or near themachines, etc.

Paul Austen
Senior Project Engineer
Electronic Controls Design Inc
Paul been with Electronic Controls Design Inc. (ECD) in Milwaukie, Oregon for over 39 years as a Senior Project Engineer. He has seen and worked with the electronic manufacturing industry from many points of view, including: technician, engineer, manufacture, and customer. His focus has been the design and application of measurement tools used to improve manufacturing thermal processes and well as moisture sensitive component storage solutions.

First &foremost...."your customer audit" They are making the request.Customers are hard tocome by. Monitors are relatively inexpensive. You do not indicate thesize of your facility so an accurate answer is difficult.A monitor at the centerof your facility is ideal but it will not provide accuracy of readings at thefar corner, say near your reflow line or your washing system. Humidity willgenerally be different in various areas of your facility The question itselfraises these questions... are you controlling humidity currently? Where are you located? A high humidityarea.. Florida? A low humidity area... Arizona? There are wireless units on the market now thatcan mo niter locations & report back to one central PC. THis providesfacility wide reading with automated recording of the factors required.

Jerry Karp
JSK Associates
Based in. Northern California since 1971. Founded JSK Associates in 1979. Actively involved in soldering, cleaning, chemistries. 30 years experience in EOS/ESD control.

Humidityand temperature monitored areas are areas wherethese parameters can possibly impact the process yields and or quality. Someareas that are normally monitored are:
  1. Solder paste and fluxstorage areas
  2. Other chemical storageareas such as conformal coating and chemistries used in the assembly process
  3. Solder paste printingareas
  4. The SMT line
  5. Board and componentstorage areas
  6. Storage for assembliesin the process of being finalized, where waiting for a few days may berequired.Inventory areas for assembled products

Peter Biocca
Senior Market Development Engineer
Mr. Biocca was a chemist with many years experience in soldering technologies. He presented around the world in matters relating to process optimization and assembly. He was the author of many technical papers delivered globally. Mr. Biocca was a respected mentor in the electronics industry. He passed away in November, 2014.

Theanswer is dependent on the uniformity of the temperature and humidity withinthe room or on the factory floor. Large areas are subject to variationsin temperature if the air handlers are not positioned properly or correctlybalanced. A common mistake is locating temperature/humidity monitorswithin the near draft path of an air conditioner vent. Ideally, beforestationing any temperature/humidity monitors, the room will be mappedespecially for temperature uniformity. Influences of operating equipment,the number of people present, outside environment, wind conditions, opening andclosing doors, consistency of air conditioner output, exhaust stack vent motorson and off, among other factors, can all impart changes to theenvironment. Even after such mapping and impact studies, I alwaysencourage deployment of multiple recording temperature/humidity monitors; onein the center and at least a couple at extreme opposite corners or a large roomor factory floor. Frequent and routine monitoring of thetemperature/humidity graphs is a must to understand environmental impact onmaterials and ensuing quality.

Gary Freedman
Colab Engineering
A thirty year veteran of electronics assembly with major OEMs including Digital Equipment Corp., Compaq and Hewlett-Packard. President of Colab Engineering, LLC; a consulting agency specializing in electronics manufacturing, root-cause analysis and manufacturing improvement. Holder of six U.S. process patents. Authored several sections and chapters on circuit assembly for industry handbooks. Wrote a treatise on laser soldering for Laser Institute of America's LIA Handbook of Laser Materials Processing. Diverse background includes significant stints and contributions in electrochemistry, photovoltaics, silicon crystal growth and laser processing prior to entering the world of PCAs. Member of SMTA. Member of the Technical Journal Committee of the Surface Mount Technology Association.