Process Input Environment -Summary

The  four environmental factors, temperature, humidity, ESD and air particles which was published in the past 2 articles are summarized in below table.  Most of these environmental factors has an impact in electronic parts manufacturing,  and some factors such as temperature and particle could also impact industry with strict hygiene requirement such as food and medical industry. 

Environmental elements	Influence by	Example Implication	Common Control methods	Measure equipment
Temperature		Chemical material Viscosity of mixture Food industry	Air conditioner	Thermometer
Humidity	Temperature	Any process which use hygroscopic material, Battery cell manufacturing Semi conductor process Most of electronic products Spray painting Plastic molding	Air conditioner Humidifier Air movement	Thermo hygrometer
ESD	Relative humidity	All Electronic related industry	ESD Smock, Wrist strap, Conductive rod, Grounding, Ionizer Disscipative material Ionizer	Digital high resistance meter, Charged-Plate Monitor, Electrostatic field-meter, Electrostatic Discharge Tester, Surface & Volume Resistance Meter, Electrostatic Voltmeter, Electrostatic Voltmeter,
Air particle	ESD	Surface finishing paint process Most of electronic parts hard disk, semiconductor, LCD Medical device	Clean room	Particle counter

Recommended guideline to control and monitor environment :-

Products that are sensitive to changes in the environment must be manufactured in a stable control environment confine by a define space such as cleanroom.  Special infrastructure or equipment must be used to modify and control the environment to suit the needs of manufacturing process for the product.  Some control mechanisms are restricted to single process operation such as winding process of jelly roll in battery cell.  There are localized control with vacuum suction and magnet to remove air particle and conductive particles within the winding equipment to minimize conductive particle in battery cell.  This is because conductive could short both anode and cathode surface of battery cell which could lead to safety hazards

Slight change in environmental are not easily detected and could have major impact on part quality.  Surveillance monitoring should be used all the time to check for any abnormality event so that immediate action could be taken. 

A good control and monitoring system and procedure setup to control and monitor environment should consist of  :-

1. Understand the raw materials to finished goods reaction to the 4 major environmental factors
2. Develop a control of the environmental factor to an optimum range suitable to manufacture parts.  This range is the optimum range which has minimal impact on product quality characteristics.
3. Invest in good infrastructure especially ESD and air particle control system.
4. Install real time monitoring/surveillance system with gage capability to measure the environmental factors with auto trigger system to warn production floor if there is any noncompliance. 
5. Measurement equipment use for monitoring must be calibrated and maintained regularly
6. If there is trigger there must be proper reaction plan documented which include

• Immediate production stop
• Investigate the cause of triggering
• Generate action plan which address root cause of triggering.
• Establish an appropriate disposition on raw materials and parts which could be affected by the abnormal event.

Real time monitoring of environment

Conclusion

Environment is silent and invisible force which does not have immediate impact on the product and therefore sometimes it is difficult to test or screen out the affected parts.  This makes it difficult to control, however it is very 

critical to to ensure environment is controlled to reduce variation of this process input.  Most of the environmental variations could lead to outliers event where it could bring serious disaster in the field if it is not controlled properly.   

Some examples are latent damage of electronic component by ESD, conductive particle in battery cell anode and cathode surface where the failure usually happens after consumer had used the product for some time.  There had been many cases serious damages in the field which could link poor environmental control during manufacturing of the parts.