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U.H.P Cleaning Process

 
 
 
 
 

 
 
 
 
 
 
 
 
 

Ultra Clean Technology Overview


Ham-Let’s U.H.P. cleaning process Ultra Clean Technology describes Ultra High Purity (U.H.P.) cleaning process which is a comprehensive approach to producing high purity fluid system components. The process consists of five interdependent links. Clean operation , cleanability, purgeability, minimal in-service particle generation and no entrapment areas.Ham-let is maintaining the integrity of the clean design through the other processes such as: manufacturing, cleaning, verification and packaging.

The specification details are as follows:

  • Product and process specifications
  • Processes and process controls
  • Process verification
  • Product testing

Where operating limits have been established, they are stated. The processes are monitored for consistency and to develop data for future specifications. Ham-Let products, processes and controls are improved continuously according to the specification that defines the current process. As Ham-let develops better technologies to meet the evolving needs of the Ultra High Purity (U.H.P.) and the process industries. The specification is revised accordingly.

Product Specification

Stainless steel: ASTM A276 & A479 with restricted composition:


Type

Carbon content %

Sulfur content %

 316 L

 0.030 max

 0.020 to 0.030

 316 L VAR or VIM/VAR

 0.010 to 0.020

 0.008 max


JK microcleanliness of VAR or VIM/VAR material is monitored in accordance with ASTM E45.

Surface Finish: Two process designators, H & E.


"H" PROCESS

"E" PROCESS

 Manufacturing with statistical
  process Control (SPC)

 Manufacturing with statistical
  process Control (SPC)

 

 Special internal polish.

 

 Electropolishing of wetted surface

 Cleaning

 Final Cleaning in Clean Room


See data in Ham-Let catalogue.


Electropolishing: Chromium to iron atomic percentage ratio: equal to or greater than 1.5 within the first 25 Å of the surface layer. Tests are conducted per Semaspec 91060573B.

UCT Process Specification


Where a process or material is designated, it referes to the specifications below:

Cleanrooms: Cleanroom class 10, work areas and cleanrooms ovens, class 10. Areas approved quarterly in accordance with Federal Standard 209E.

Deionized (DI) Water: Controlled final resistivity level of 18 M Ω cm. Other properties monitored to ensure consistent processes:

  • Intermediate resistivity
  • Bacteria
  • Particles
  • Silica

Ultrasonic Cleaning System


Ultrasonic Cleaning System also monitored for:

  • DI water temperature at each wet process station
  • Drying process temperature
  • Resistivity of DI water at final ultrasonic rinse
  • Ultrasonic generator power outputHelium:

Helium:Clean, dry 0.02 µm filtered.

Process Sequence


Material Analysis


Ham-Let products are made of raw materials that meet restricted standards. The chemical analysis and mechanical properties surpass ASTM requirements. Low-carbon materials are selected for components which must be welded, in order to avoid carbide precipitation. Likewise sulfur content is carefully controlled to ensure consistent welds. Selected fittings and bodies of certain valves are made of VIM/VAR stainless steel material which contains less sulfur. The objective is to lessen inclusions, improve the surfaces which are electropolished and above all to reduce surface defects. Each heat of this VIM/VAR stainless steel is verified by a test method based on ASTM E45 that uses a standard metallographic examination or scanning electron microscopy (SEM) to determine JK ratings at 100 and 1000x

Manufacturing with Statistical Process Control (SPC)


Surface finish, dimensions and various other product attributes of fittings and valves are regulated by Ham-Let through a statistical process control (SPC). SPC ensures continuous monitoring of parts, instead of inspecting finished products – thus ensuring that all parts meet spec limitations. SPC is a pro-active approach that allows Ham-Let to promptly identify manufacturing process changes that could affect products – thus ensuring that adjustments are made so that reject parts are not produced. This “on-line, real-time” monitoring ensures more consistent and reliable products, more efficient production processes, and more competitive pricing as customers do not have to absorb hidden costs of production line problems.

Surface Finishing


A quality surface finish ensures that cleaned parts meet performance specs in service. This includes whether or not the device can be cleaned and purged quickly and completely so that no stray particles will be trapped or accumulated.  Finished parts are carefully examined. ANSI/ASME B.46.1 standards apply to the surface roughness measurements.

Measurements are taken on each bore of the fitting or valve over the maximum available traverse length, but not on tapered surfaces, intersections, or welds. Certain fitting components of longer length may have a minimal inside diameter mismatch. Two surface finish processes are available: “H” and “E”. Average and maximum Ra max values for production samples of U.H.P. products are listed in HTC catalogue.

Electropolishing


Electro-polishing is the process used for internal surfaces of fittings and valve bodies. This ensures a corrosion-resistant surface layer of chromium oxide which is passive. After manufacturing or after any mechanical process, the following sequence is followed for cleaned U.H.P. products:

  • For a uniform surface, the UHP devices are precleaned
  • Electropolish and a (DI) deionized water rinse
  • Where appropriate, passivation and DI water rinses follow.

Reference Spec: SEMI F19-95.

Deionized (DI) Water Cleaning and Drying


Final cleaning is the crucial touch of making the perfect UHP part – therefore Ham-Let employs a DI water cleaning process prior to assembly, testing and product packaging. The UHP parts move straight from production into a multi-stage DI water rinse process. After that, they receive a high-velocity DI water rinse in a class 10 cleanroom. UHP cleaning process: Nitrogen is used to blow off excess moisture. The fittings are then dried in a class 10 cleanroom oven.

Reference Spec: SEMI E49.2-0298.

Class 10 Assembly, Testing and Packing


Following the strict production procedures, UHP parts are transferred to class 10 workstations in a class 10 cleanroom where the parts are assembled, tested and packaged, so as to avoid any possibility of airborne contamination. Ham-Let uses nylon inner bags to prevent contamination and an outside bag of polyethylene to ensure a strong, break-resistant package.

Fittings Packaging: The inner bag is vacuum sealed to protect the fitting from contamination and to prevent it from cutting the bag. The box is padded.

Background


Ham-Let also employs ASTM test methods based on SEMATECH test methods (SEMASPECs) for additional random sample checks from production lots. These methods provide reproducible data and they are based on industry standards. The gathered data can also be used for additional process control specs.

Surface Analysis


SEM/EDX (energy-dispersive X-ray) analysis is used to monitor production samples (since surface analysis is not part of the average surface roughness measurements). This process uses a standardized system of operating parameters to ensure that all the results are consistent. Randomly selected sample surfaces are examined at 3600x. Test methods are based on ASTM F1372 and ASTM F1375. Surface defects are counted, measured and analyzed using SEM. Base material and any inclusion material or contamination can be identified by EDX when necessary.

Surface Composition


Auger electron spectroscopy (AES) analysis is used to ascertain that a corrosion-resistant, passive layer of chromium oxide has been formed, based on test method of SEMSPEC 91060573A-STD. This AES analysis measures iron, chromium, carbon, oxygen and nickel. Within the first100 Å (10 nm), the chromium-to-iron atomic percentage ratio must reach values of 1.5 – greater or equal to. To verify the complete cleaning and rinsing process, surface quantities of the following contaminants are verified:
calcium, sodium, phosphorus, chlorine, sulfur and silicon oxide.

Moisture Analysis


Ham-Let employs a highly sensitive (0.1 ppb moisture concentration) moisture outgassing test to monitor the consistency of drying processes. The products are tested in a dry, controlled chamber. Continuous purging with ultra clean nitrogen ensures no contamination. Nitrogen passes through the test component at a rate of 1 std L/min and a gauge pressure of 30 psi (2 bar) (based on ASTM F1397) and is followed by a bake-out sequence once the test piece has dried-down.

Helium Leak Test


Ham-let conducts Helium leak tests with ultra clean process Helium in accordance with ASTM E98, Method A. UHP products are tested in a class 10 environment.

Face Seal Fittings: Samples are Helium leak tested to ensure that they can be assembled leak tight to a rate of 3 x 10-11 std cm3 /s.

Particle Contribution Test


Ham-let tests on Fittings shows no more then 4 particles of 0.01 micro meter and above, measured by use of Particle Counters.
Tests are performed per Semaspec Standard 90120390 B.

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