Analog Systems

  The Oldest form of measuring devices.  These devices acted independently to measure a given quantity of constantly changing measurements in a metered format which would make the quantity be measured.  To a computer the measuements didn’t mean anything until the measurement was tranformed to a changing signal based in milliamps or volts that could constantly change.  The measurement could then be input into the computer for evaluation and programmed responses, based on given setpoints, would monitor a measured device or what is known as a point in the field, reacting to a given casuality from that point.

Examples of analog devices are clocks, speedometers, rotameters, pressure guages, magnehelics (low pressure guages), flowmeters, current or ampmeters, hertz or frequency meters, voltmeters, weight scales, radio frequency scales, life safety monitors, and various other devices that have meters, scales, or a line showing the measurement.

Why you don’t use a teflon gasket for cylinder connections

The problem happened a long time ago for me we got called in to look into why our Chlorine cylinder was starving the process with gas.  After further investigation to the matter we found that the cylinder pressure would drop off after running for a while.  We pulled the gasket(at the cylinder valve connection) and changed the gasket to a Kel-F gasket.  The process didn’t experience that problem after that.  We were later told that the cylinder connection would cold flow the teflon, the teflon would swell and begin to choke off the flow of gas to the process.  Since that day it’s recommended to use Kel-F gaskets for cylinder connections due to swelling experienced with the teflon.

What’s going on a

A Ten Step Life Cycle program for Chemicals and Gases entering the Fab.
      By following the standard and understanding the life cycle of chemicals as they enter and cycle through the steps, the chance of misappropriating the chemical, and chance that the chemical is going to leak, is diminished.  The Cycle starts as:
  1. Acceptance– When the chemical or gas is delivered to the site, Check for:
  • Correct labeling (is the container listing all the correct labels),
  • Leaks, is the cylinder, container or bottles contained in the box noticeably leaking
  • Check to see where the chemical is to be used in the fab and where,
  • Check if the delivered chemical is what was ordered,
  • Storing the container properly, all storage is designed to contain a catastrophic failure  
  • Inspection– After the chemical is properly stored,
  • Protocol to verify connection to systems purity, and mechanical integrity should detail how a critical chemical is inspected.
  • Inspection again of proper labeling all contents clearly labeled and correctly applied
  • Inspection of the container for leaks.


  • Storage is designed to contain the total contents of any container through a catastrophic event.  Segregation of the different class of chemical must be maintained through the storage life of all containers being stored,in an area.  Flammables with other flammables, acids away from bases, flammables or toxics away from oxidizers, by following the rules of chemical segregation the facility will have less problems.  Restraint of containers from moving or falling down is also essential to good storage practices. 

Basic Chemicals found in a Fab


There are basic chemistries found throughout a Semiconductor Fabrication Factory or what is commonly known as a Fab.  These chemistries are the work horses found throughout the Wafer Processing recipes of how to make a wafer.  The chemicals are Sulfuric Acid, Hydrogen Peroxide, Hydrochloric Acid, Hydrofluoric Acid, Ammonium Hydroxide, IPA, Ethyl Lactate, Phosphoric Acid, & Photoresist.  What I can tell you if you have a basic understanding of these chemicals and what their handling properties are, this knowledge will translate into a greater understanding of the properties of other chemicals.  So lets start with Sulfuric Acid.

Teach the way you learn

Im going to begin my teaching and website construction of, the same way I learned over the years and develop my practice of work, which could also be said going to work everyday and practicing without even thinking I was practicing for what I would ultimately find to be my mastery of the electronics disciplines I work which wouldn’t even be considered work to me because i enjoy it so, much.  It would and could be considered my biography of learning.  My real joy of this massive endeavor is that Im still around doing the work, I’ve been developing.  My biggest joy is getting the respect by my customers, both internal and external and i love the engagement as the day to day work is a learning experience adding to the project.  My biggest problem to overcome is the distractors of the day, or what could be considered time wasters from producing my galaxy-class great works of training modules information cut sheets.  Even though the allure of watching TV, watching a good episode of “my programs” I would watch has the act of losing yourself for a while, i need to stop being distracted from the goal of producing work from a Great Master.

Leak sensors seem to be a theme of late

In the last few weeks I’ve learned more about leak sensors then i care to know.  We have been dealing with nagging sensors that have different things going on with them.  So what i know about sensors is they talk about “PNP” type and “NPN” type this sounds a lot like transistor logic.  This logic could be referring to the profiling in typical fashion that a transistor would be drawn electrically. Also from what i was told the sensor would be profiled to be a short and close on sensing moisture.  Or the digital would be a zero and go to one upon sensing.  The other type sensors are the “NPN”,  these sensors work opposite of the way the PNP sensors work.  They are closed and alarm open if sensing moisture, or are high and go low on the sense, or another way to say it, are signaling one and go to zero with water… more on this subject later when i understand more about them.

Auto-recovery program saves the day!

I got a call last Tuesday late, when the techs onsite found both systems delivering gas and were both online.  After further investigating why both systems were online, it was found that a brown out condition existed onsite.  Due to the extraordinary services the gas cabinet controller recovered after the electrical event to keep supplying critically needed gas to the Fab thereby avoiding the expense of an unplanned shutdown.  I found out the nature of this program is called an auto-recovery program to keep systems online during a electrically challenged event.  To recover the systems back to normal operations you need to change states of the internal flags in the programming for the Gas Cabinet controllers to be cleared and readied for one system online and the other to be in standby. This one feature of the controller’s is not widely published but would enhance the “selling features” of the equipment.

Perseverance pays off correcting an alarm

A pesky alarm had been plaguing our site for the last half a year. The issues, trying to track down where this alarm was, to who would be responsible for it, to why is this alarm even being monitored were some of the responses being said.  I finally got a lead on who to call regarding the panel when the tech arrived I proceeded with him to the suspected panel and found the panel to be confusing in what it was saying.  According to the tech, the panel was indicating no problem but was outputting to the site monitoring system a trouble, after further investigation the point of connection was mounted to the correct set of points, normally open, close on alarm.  I’ll explain this in a future post but now the status according to the site monitoring system was correctly issuing the correct response, no alarm.  Much gratitude ensued following the “Clearing of the alarm” and it was said that only through  my perseverance was this alarm corrected.  Also asking the right questions to the tech, why would our monitoring system be seeing an alarm.