Water Specifications :

Water Quality Specifications for the Microelectronics Industries :

NCCLS / CAP Reagent Water Specifications :

USP XXIV Purified Water Specifications:

Remark: Chloride, Sulfate, Ammonia, Calcium, Carbon Dioxide, Heavy Metals, and Total Solids requirements replaced by conductivity measurement; Oxidizable substances requirement replaced by TOC measurement

Frequently Asked Questions :

Q1: What is High Purity Water?
A1: For the purpose of manufacturing electronic components, pure water means almost free of extraneous minerals, particles, organisms, organics and dissolved gases. The evolution of technology and the continuous quest for even more advanced electronic products has almost pushed the requirement for pure water to a limit. Water purity specified by some semiconductor manufacturer has reached 99.999999999%. In terms of mass, such a purity means various contaminant levels in the range of a few tenths of trillion gram per liter of water.

Q2: Why do I need High Purity Water for cleaning and rinsing?
A2: In its pure state, water is one of the most aggressive solvents (aqueous solution) known. Water, which is called the "universal solvent", will dissolve virtually everything exposed to it to a certain degree.

Q3: How can High Purity Water be produced?
A3: To High Purity Water, various treatment processes are synergistically used which can be grouped under the following categories:
1. Filtration
2. Membrane Separation
3. Ion Exchange
4. Degasification
5. UV Sterilization
6. UV Oxidation of Dissolved Organics

Q4: What is Ultrafiltration (UF)?
A4: Ultrafiltration is a pressure driven membrane separation operation in which particulates, colloids, emulsified oils, and macromolecules are separated from a liquid feed stream upon passage through a porous semi-permeable membrane. The separation is based primary on the size of the species in the liquid relative to the size of the membrane pores.

Q5: How Ultrafiltration Membranes (UF) are rated?
A5: UF are rated on their ability to remove certain sized molecules. The “size” of a molecule is roughly proportional to its weight, and therefore the MWCO specified for an UF indicates the minimum size (weight) of molecules that will be removed by a particular UF device.

Q6: What is Osmosis?
A6: Osmosis is the passage of a liquid through a semi-permeable membrane.

Q7: What is Reverse Osmosis (RO)?
A7: In osmosis, there is a tendency for liquid to go from an area of less concentration to an area of more concentration through a semi permeable membrane. This is an osmotic flow. A semi permeable membrane is a membrane, which allow one component of a solution to pass through it and not the other. The osmosis continues, the level of the concentrated solution rises until the pressure created by Osmotic Head equals the Osmotic pressure created by the different concentration of the two solutions. This is an Osmotic Equilibrium. If pressure is applied to the concentrated side, Reverse Osmosis will take place. The pressure causes a flow through the semi permeable membrane into the diluted solution as a result of the passage of water molecules through the membrane while the mineral ions are rejected. The semi permeable membrane acts as a barrier to ions and does not allow them to pass through into the dilute solution. When applied to water, this means that the product water has a reduced total dissolved solids content.

Q8: How does water migrate through the Reverse Osmosis Membranes ?
A8: The exact mechanism of the transport of water across a semipermeable membrane is still subject to debate. The type of membrane in use for water has pore sizes of less than 0.05 micron with most of the pores probably in the size range of 0.02 micron or less , i.e., 200 angstrom. Since the pores will be lined with polar hydroxyl groups, hydrated sites, and less polar acetate groups, the most probably mechanism for the transport of water through the membrane would appear to be the relatively low energy exchange of water molecules from one polar group to another in the pores involving diffusion type process. Hydrated ions, on the other hand, bind water more strongly and would require more exchange energy for the same process. Hydrated ions therefore would move through the pores by a much slower process.

Q9: What is Deionization ?
A9: Deionization is an ion exchange processes. It uses certain types of synthetic resins in the proper state and arrangements to remove most or all of the total dissolved solids, in the form of ions, from water. Water with ions taken out by ion exchange is deionized water, or ion free water.

Q10: What is Ion Exchange ?
Ion exchange is the substitution of one kind of positive ion for another. Or the substitution of one kind of negative ion for another. We can call it Ion Trade.

A clearer definition might be: Ion exchange is the reversible interchange of ions of similar electrical charge between a solution and a solid insoluble body in contact with the solution. The solid insoluble body is called an Ion Exchanger. The most typical solution but by no means the only one is water. The commonest ion exchanger is soil.

Q11: What are ions ?
A11: Sodium atoms react with chlorine atoms to form sodium chloride (table salt). When table salt dissolved in water, it ionizes. The sodium atom gives up an electron and becomes a sodium ion with a positive electrical charge. The chloride atom gains an electron and becomes chloride ion with a negative electrical charge. Ions, then, are electrically charged derivatives of atoms or groups of atoms, but are neither atoms nor molecules. Some ions have positive electrical charge; some have negative electrical charge. Ions of metal have positive charge. Ions of non-metals have negative charge. Hydrogen, a gas, can have either a positive or a negative charge depending on the chemical compound of which it is a component. Ions of only one type of charge cannot exist by themselves. A positive ion must have a negative ion in the immediate vicinity, and vice versa.

Q12: What are TDS ?
The letter TDS refer to Total Dissolved Solids in water. Hardness minerals are only a part of the total dissolved solids. TDS for ion exchange calculation is the sum of the cations or the sum of the anions, depending on which resins are being considered.

Q13: What is Regeneration ?
A13: Regeneration is the conversion of an ion exchange resin to a desired ionic form. Regeneration involves the passage of a regenerant containing high concentrations of a desired ion through a resin bed to create an equilibrium situation that favors removal of some portion (ideally most) of the ions accumulated during the service run, leaving the bed in an ions form that is again useful to the process. The regenerant may be passed through the bed in the same direction as the service flow (co-current regeneration) or in the opposite direction from the service flow (counter-current regeneration).

Q14: What is Electro-deionization (EDI) ?
A14: The EDI process employs an alternating arrangement of anion and cation permeable membranes, between which mixed bed ion exchange resin is sandwiched. Desired flow rates are obtained by aligning numerous membranes/resin assemblies (known as dilute spacers) hydraulically in parallel, and electrically in series. Separating the dilute spacers and forming the waste compartment are screen type concentrate spacers. The combination of a dilute spacer and an adjacent concentrate spacer is sometimes referred to as a cell pair. By applying a DC electric potential across a stack of cell pairs, ions move from one stream to another, effecting a separation. Diluted product water is produced in one stream (diluting stream) and concentrated waste water is produced in the other (concentrating stream). As water flows down the length of the diluting stream, cationic contaminants first attached onto cation exchange resin beads. Under the influence of the electrical field, these ions will migrate through the resin in the direction of the negatively charged cathode. Once the ions reach the cation permeable membrane, they are pulled through into the concentrating stream. An anion permeable membrane on the other side of that stream prevents further migration, effectively trapping the cations in the concentrating stream and allowing them to be flushed to drain. The process for anion removal is similar, but in the opposite direction, toward the positively charged anode.

Q15: What is a Forced Draft Degasifier?
A15: The forced draft degasifier is a vertical, cylindrical vessel containing essentially polypropylene packing materials. Water entering at the top of the vessel trickles downward while a blower located at the base forces a counter-current air stream against the falling water. The packing inside the vessel provide large free volume to avoid pressure drop and sufficient surface contact area for gas and liquid phase interface. Since carbon dioxide is more soluble in the gas phase, the increasing gas-liquid contact area results in the removal of the majority of the carbon dioxide by the upward airflow.

Q16: What is Catalytic Oxygen Removal System (CORS) ?
A16: The catalytic oxygen removal system (CORS) uses a palladium doped anion resin to catalyze the reduction of dissolved oxygen in water or other solutions with either hydrogen or hydrazine. The reaction takes place at ambient temperatures and a pressure of approximately 100 psi. The dissolved oxygen level can be reduced in a single pass from the 6.0 to 8.0 ppm range down to less than 10 ppb, less than 5 ppb, less than 1 ppb – depending on design. The reaction by-products are water for hydrogen system and nitrogen for hydrazine. The anion resins acts only as carrier for the palladium catalyst and is not regenerated.

Q17: What is Membrane Contactor (Membrane Degasifier) ?
A17: Membrane contactors are devices, which can be used to permit mass transfer between a gaseous phase and a liquid phase of a materials without dispersing one phase into another. The membrane contactors utilize a hydrophobic porous membrane made of PP materials. The membrane material is fabricated in the form of a hollow fibers which are bundled together inside a SS outer shell. The hydrophobic porous membrane acts as a support to prevent disperse of the water while allowing the water to come to contact with the gas phase. Vacuum is applied to reduce the partial pressure of the gas phase. And as the partial pressure of the gases on the gas phase is reduced the concentration of the gases remain dissolved in the water is reduced in proportional to the partial pressure.

Q18: What is Vacuum Degasifier?
A18: Vacuum Degasifier are typically tall columns filled with packing or trays and are used to bring a liquid phase in contact with a gas phase for the purpose of removing dissolved gases from the liquid. The liquid runs from the top of the column down around the packing. The packing creates a large surface area for the gas phase to contact the liquid phase.

Q19: What is Ultraviolet Light?
A19: Ultraviolet light is a form of electromagnetic or radian energy, radian travels, in the form of waves, in straight line paths and in all directions from its source. The wave lengths range from very long radio waves to very short X-rays. The most familiar part of the spectrum is a narrow band of wavelengths visible to the human eye. Another band with wavelengths shorter than those of visible light, and not visible to the eye, is the ultraviolet part of the spectrum. Ultraviolet radiation can cause changes in living matter. When applied to microorganism, it causes changes to the DNA of the microorganism rendering them unable to multiply.

Q20: What is a Ultraviolet Lamp?
A20: Ultraviolet lamp works on the following principles:
An electric arc is struck through an inert gas carrier (usually proprietary), in a sealed special glass tube. Heating from the arc cause vaporization of the small amount of mercury contained in the sealed tube. The mercury when vaporized becomes ionized and in the electric arc gives off UV radiation.

Q21: What is Validation?
A21: Establishing documented evidence which provides a high degree of assurance that a specific process will consistently produce a product meeting its pre-determined specifications and quality attributes.

Q22: What is Validation Protocol?
A22: A written plan stating how validation will be implemented including test parameters, product characteristics, product equipment, and decision points on what constitutes acceptable test results.

Q23: Why Process Validation is necessary?
A23: Process validation is required, in both general and specific terms, by the Current Good Manufacturing Practice Regulations for Finished Pharmaceuticals, 21 CFR Part 210 and 211, and of the Good Manufacturing Practices Regulations for Medical Devices, 21 CFR Part 820, and therefore, is applicable to the manufacture of Pharmaceuticals and medical devices.

Q24: What is Validation Master Plan (VMP)?
A24: Validation Master Plan is a document that describes the approach and methods to be used during the entire validation effort. The master validation plan is the SOP for the entire validation.

Q25: What is Installation Qualification (IQ)?
A25: Installation qualification (IQ) is a protocol to check that the equipment, pipe, and instrumentation are installed properly and in accordance with the design documents.

Q26: What is Operational Qualification (OQ)?
A26: Operational Qualification (OQ) is a protocol designed to ensure that the various equipment operates as designed. This protocol includes instrument calibrations, flow rates, pump rotation, and other system factors.

Q27: What is Performance Qualification (PQ)?
A27: Performance Qualification (PQ) measures the system’s overall performance to establish its level of control. The PQ will consist of samples that are taken and tested against the United States Pharmacopoeia (USP) monograph tests and other internal standards.

Q28: What is Standard Operating Procedures(SOPs)?
A28: OSHA’s Laboratory Standard (29 CFR 1910,1450) requires that all Standard Operating Procedures include health and safety information. An SOP is a written procedure that all workers must follow when performing a routine laboratory task. Most SOPs detail the steps of an operation in the order in which they should be performed.