What is RGA Testing?

We have already discussed the importance of the hermetic leak test  on these pages

And yet the tests involving containers, environments and hermetic packaging do not end there.

Another important test is called RGA Testing, which stands for Residual Gas Analysis Testing, a procedure that is less widespread in industry but of vital importance for some specific sectors.

Let's see it together.

What is RGA Testing Used For?

Modern vacuum sealing techniques can eliminate up to 99.9% of the air present.

And that 0.1% you have left?

That is the object of RGA Testing.

RGA Testing analyzes the residual gases present in a container or vacuum environment to determine their quantity, composition, and actual hazardousness.

Contrary to popular belief, RGA testing is not used on mass-produced vacuum containers but rather in two specific sectors: aerospace and electronic components.

In these sectors, RGA Testing plays similar roles but with important differences.

In the aerospace sector it is used to analyse the residual gases of real environments, i.e. chambers thermal vacuum.

While in consumer electronics its object is the so-called packaging of microelectronic components: hermetic casings that surround the processors and the most delicate components of an electronic device.

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How RGA Testing Works

As you can imagine, depending on the environment to be tested, RGA Testing takes different forms, although the substance remains the same.

Whether it is a thermal vacuum chamber or the packaging of microelectronic components, the test consists of two phases.

First, a probe is introduced into the vacuum environment, which extracts the gas.

This gas is then analysed with specific laboratory instruments, such as a mass spectrometer, capable of separating the various types of extracted gases and therefore conducting both a qualitative and quantitative analysis.

The international standards that concern the various types of RGA Testing are MIL-STD-883, ASTM E595 and JESD22.

RGA Testing and Environmental Chambers

What do environmental chambers and climate tests in general have to do with waste gas analysis?

As in various cases we have addressed, climatic chambers offer a supporting role in some specific cases.

These cases almost exclusively concern tests conducted on small samples, such as the microelectronics packaging we discussed. To conduct tests on certain types of gases, the sample to be analyzed must first be thermally conditioned. Gases, as we know, behave differently at different temperatures, and there are some procedures that, for example, require conditioning the sample at 100°C to ensure a proper analysis of the gases contained within.

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FDM Environmental Chambers for RGA Testing Conditioning

FDM environmental chambers are capable of reaching extreme temperatures and therefore thermally conditioning the RGA Testing samples, reaching the degrees required by conventionally accepted procedures.

Furthermore, our environmental chambers can be appropriately modified to meet the specific needs of each customer.

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Reference Standards

• MIL-STD-883 Method 1018 — Internal Gas Analysis. Military standard for internal gas analysis in hermetically sealed microelectronic packages; typical limit H₂O ≤ 5,000 ppm.
• MIL-STD-750 Method 1018 — Equivalent to Method 1018 for discrete semiconductor devices.
• ASTM E996 — Standard Practice for Reporting Data in Auger Electron Spectroscopy and X-ray Photoelectron Spectroscopy (Reference for Related Surface Characterization).
• ASTM F1982 — Standard Test Methods for Analyzing the Interior Atmospheres of Hermetically Sealed Microelectronic Packages.
• ISO 3530 — Vacuum technology – Mass-spectrometer-type leak-detector calibration.
• ECSS-Q-ST-70-04C — ESA Space product assurance – Thermal testing for assessment of electronic components.
• JEDEC JESD202 — Method for Characterizing Residual Gases in Hermetic Packages.

Authoritative Sources

• DLA – Defense Logistics Agency (MIL-STD database). Agency that publishes the MIL-STD-883/750 standards referenced by the AEC and space.
• JEDEC Solid State Technology Association. Publishes JESD202 and related standards for microelectronic test packages.
• ASTM International. ASTM F1982 Methods for the Analysis of Internal Atmospheres of Hermetic Packages.
• ESA – European Space Agency. Publishes ECSS for the qualification of aerospace electronic components with RGA requirements.

Frequently Asked Questions about RGA Testing

What is Residual Gas Analysis and when is it mandatory?

Residual Gas Analysis (RGA) measures the composition of gases inside hermetically sealed cavities of electronic, hybrid, MEMS, and optical device packages. The standard MIL-STD-883 Method 1018 involves puncturing the package in a vacuum chamber (< 10⁻⁵ Pa) coupled to a quadrupole mass spectrometer with a range of 1-100 amu, followed by evaporation transient analysis to quantify H₂O, O₂, N₂, Ar, CO, CO₂, hydrocarbons, and hydrogen. Mandatory for the qualification of MIL/aerospace Class H/K and AEC-Q100/Q101 automotive Grade 0/1 devices. The most stringent limit is H₂O ≤ 5,000 ppm (0.5%), the threshold above which internal condensation forms with corrosion and electrical shorts at temperatures < 0 °C.

How do you distinguish between welding gas and contamination?

The typical sealing atmosphere is N₂ (>99%) or N₂/He mixtures to facilitate subsequent fine leak testing. The presence of O₂ >1,000 ppm indicates contaminated backfill or incomplete sealing; residual Ar comes from the inert atmosphere of laser/parallel gap seam-sealing welding. Hydrocarbons (C_nH_m, mass 40-100 amu) come from outgassing of flux, epoxy resins, and silicone adhesives; H₂ comes from electrolysis/corrosion or dealing with Ni-plating; CO/CO₂ from thermal degradation of polymers. A bakeout at 125-150 °C for 8-24 hours under vacuum reduces the outgassing of organic materials. An out-of-spec RGA requires root cause analysis (FA) with deformation of the suspect components.

What sensitivity and uncertainty does a quadrupole RGA achieve?

RGA quadrupole mass spectrometers operate at base pressure < 10⁻⁷ Pa, typical sensitivity 10⁻¹⁴ torr·L partial (equivalent to 10–100 ppm in 10–100 μL free volume). Unity resolution over the entire 1–100 amu range readily separates H₂O (18) from N₂ (28) and CO (28, requires cracking pattern analysis). Quantification uncertainty for H₂O is typically ± 500 ppm or ± 15% of the value (whichever is greater) according to MIL-STD-883 Method 1018. Calibration uses standard packages with known injected amounts (NIST traceable) or calibrated H₂O permeation. Puncture temperature and desorption transient are critical: recommended gradient 100 °C, acquisition time 30-120 s.

What minimum volumes do RGA allow and what to do with cavities < 0.1 cc?

MIL-STD-883 Method 1018 specifies a minimum cavity volume of 0.1 cm³ (100 μL) to have a signal above the bottom of the vacuum system. TO, LCC, and PGA packages retract easily; MEMS and microoptics often have cavities of 1–50 μL, below the threshold. For low-volume devices, alternative techniques are used: laser ablation coupled mass spectrometry (aperture with a 1064 nm Nd:YAG laser), an optical moisture sensor based on an internal miniaturized FTIR (pre-installed during assembly), or a CMOS dew point sensor integrated as a companion die. For cavities < 0.01 cm³, data is considered qualitative. Condition B (5,000 ppm H₂O) is maintained as a requirement even for small-volume packages through statistical process control on representative batches.