Ultra Fine Leak Test System

Ultra Fine Leak Testing

Compact electronic components and MEMS parts such as angular velocity sensors and infrared image sensors are required to maintain a sealing performance within products that lasts over many years, and therefore a higher level of airtightness is required. At FUKUDA, we have developed the ‘Capsule-Accumulation Method’, a high-sensitivity helium leak detection technology as part of our ultra fine leak testing technology. The MUH-0100 series dedicated ultra fine leak airtight testing system features the Capsule-Accumulation Method.

Ultra Fine Leak Test System

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System Testing Range

Considering background effects, the helium leak volume in previous methods could only in practice reach the 10^-10Pa・m³/s(He)range. This technology enables further leak volume testing down to the 10^-15 Pa・m³/s (He) range*.
* The leak volume that can be tested varies by test parts type and conditions of use.

Fig 1. MUH-0100 Leak Testing Range

“Capsule-Accumulation Method”

In order to detect fine helium leaks from test parts, the Capsule-Accumulation Method employs a small-volume capsule inside a large-volume chamber. Ultra fine leak testing is conducted by the following three steps:

Testing Process
(1) After creating a vacuum in the capsule (containing the test parts) and chamber, the capsule is closed,
and helium is added to a level where it can be detected with a mass spectrometer.
(2) The capsule is opened, releasing the gas inside the capsule into the chamber.
(3) The helium dispersed becomes a molecular flow, is passed through an orifice, and is then tested by the mass spectrometer.

Fig 2. Principle diagram

Characteristic of “Capsule-Accumulation Method”

The helium background was significantly reduced
This enables testing of ultra-fine helium leaks.
Helium leak testing performance* 4x10^-15Pa・m³/s（He）～
*For an accumulation time of two hours.
The equipment is dependent on test conditions such as the bombing conditions, capsule size, and exposure time.

Reduction in non-target gases, which cause errors
A heater or cryogenic pump is no longer necessary, making startup time and maintenance equivalent to a
regular helium leak detector.

Calibration of the helium accumulation volume can be carried out with a commercially-available standard leak device

Fig 3. Sensitivity of the helium leak

Fig. 3 shows the accumulation time (x-axis) against the sensitivity of the helium to be tested (y-axis).

Points to note when testing ultra fine leaks

Package materials
Helium gas permeation will occur if glass is included in the package or bonding surface materials. Take great care with the materials used. The helium gas permeation deposit tolerance quantity must be no more than approximately 1/10 of the tested leak volume.

Gross leaks
If gross leaks are present, the helium gas inside the test parts will escape quickly, rendering the fine leak test value inaccurate. It is necessary to accurately test for gross leaks at 1×10^-6Pa・m³/s （(Equivalent standard leak rate). We recommend our gross leak test system for gross leak testing. Maintaining an internal volume of at least 0.1mm³ in the test piece is also necessary.

Testing methods/procedures
・Refer to the application notes (examples of procedures etc.) for testing methods and procedures for individual test parts.
・We can send technicians to conduct on-site operations on request. Please contact us regarding