Leak Testing

Our full clean room services include a range of testing including leak testing, for helium and positive pressure testing. Macfab’s focus on providing a low total cost of ownership through quality work is added through our leak testing of prototype and production parts.

Leak testing is a form of Non-destructive Testing (NDT). This form of testing allows validation of the part and process while not requiring it to be a sacrificial (scrap) part. Using our Agilent vacuum and leak detectors combined with our innovative custom testing systems, your parts will arrive as expected.

Leak Testing in Static and Dynamic Conditions

As a supply chain partner, focusing on mutual success, Macfab conducts leak testing on all prototype type parts that require it. If a crack or hole is found, we careful review our internal process and retest the part. Our engineering team has developed fixturing to allow our testing to be done in both static (stationary) and dynamic (moving) conditions painting a more realistic

As a part moves into production, so too does our leak testing. The focus remains to identify defects that can only be found using this testing method. Our engineering and quality teams develop sampling plans based on consistency of the process and experience, to conduct periodic inspection of the parts validating the process remains in control. A stable process generates steady a flow of products to our customers.

Macfab practices these leak testing methods in order of sensitivity:

Air Pressure (Vacuum) Decay

Air Pressure (Vacuum) Decay utilizes air at a vacuum up to 80 pounds per square inch (PSI). This process reduces the variation caused by temperature, has a higher throughput compared to other methods, and can detect multiple defects if present.

Bubble Immersion

The Bubble Immersion method is used to test welds and sealing of assemblies. The test piece can be pressurized at 3 to 40 PSI with a maximum of 125 PSI and submerged in a tank of water. The inspector then looks for bubbles indicating a defect.

Helium Mass Spectrometry

At nearly double the sensitivity of the bubble test method is Helium Mass Spectrometry 100x to 1,000,000x. This method requires being able to develop a negative pressure difference between the test part and the atmosphere. Using this method, a quantitative measurement volume of cubic centimeters per second (atm cc/sec) of the leak rate can be recorded. Depending on the configuration of the part/assembly, the precision with which this testing is done, the location of the leak(s) can often be identified on the part.

Highlighted in yellow are the testing methods Macfab performs, additional information in the table are other testing methods and their comparison for reference.

Method	Quantifiable Result	Locate Leak	Global ¹	Go/ No Go	Test Media	Test Volume Dept.²	Relative Cost
Air Pressure (Vacuum) Decay	Yes	No	Yes	Yes	Air	Yes	Medium
Mass Flow	Yes	No	Yes	Yes	Air	Yes	Medium
Dye Liquid Tracers	No	Yes	No	No	Liquid	No	Low
Bubble Immersion	No	Yes	No	No	Air	No	Low
Thermal Conductivity Sniffing	Limited	Yes	No	Yes³	Helium	No	Low
Sulfur Hexafluoride (SF6) Sniffing	Limited	Yes	No	Yes³	SF₆	No	Low-Med
Helium Mass Spec Sniffing	Limited	Yes	No	Yes³	Helium	No	Med-High
Helium Mass spec Atmosphere Accumulation	Yes	No	Yes	Yes	Helium	Yes	High
Helium Mass Spec Hard Vacuum	Yes	Yes	Yes	Yes	Helium	No	High
Trace Gas Mass Spec Hard Vacuum	Yes	Yes	Yes	Yes	R134_a, SF₆, Air, H₂, NO₂, CO₂	No	High

Clarification Points
1. The test method measure the global leak rate of the part, versus individual leaks.
2. The test volume significantly affects the test cycle time and/or sensitivity.
3. Result may vary based on skill of operator.

While no process is error free, our investment in multiple methods and a range of leak testing sensitivities provides us with options to meet a customer’s range of expectations from engineering specifications, quality verifications, and supply chain requirements.

Let’s discuss the option best suited for your part and total cost of ownership.