1. Impacts of Electronic Equipment on Outer Space
When electronic equipment is used in space, such as satellites, it must withstand extremely severe operating environments, such as the effects of radiation and severe temperature changes.
If a satellite fails, it cannot be repaired, and there are significant impacts such as cost losses (launch costs for HII-A rockets: approximately 10 billion yen, satellite manufacturing costs: several tens of billions of yen) and satellite becomes to space debris ( Fig. 1). Therefore, high reliability is required for components of space applications.

Fig.1 Image of impact on spacecraft in space environment
(The red letters in the frame are considered items in the design.)

2. Requirements for space-use components
General requirements for components for space applications are listed below.

・ Operating temperature range :-55 ℃ ～ +125 ℃
・ Hermetic package
・ High vibration resistance
・ Control of outgas and flammability
・ Long-term reliability
・ Radiation tolerance
・ Lot assurance test
・ Traceability at lot level

3. Policy for reliability assurance of oscillators for space use
High reliability is guaranteed by incorporating the following four points into the design and quality control, including the requirements for components for space applications, as oscillators for onboard satellites.

(1) Reliability assured at the mounted onboard component level
(2) Oscillator Structure Considering Environmental Resistance Performance
(3) Implement thorough process control (check and inspect each process)
(4) Conducted quality verification tests for screening and Lot assurance
Common Specification for Reliability Assurance Mixed Integrated Circuits for Space Development: Applied to JAXA-QTS-2020
Each item is described in detail below.

(1) Reliability assured at the onboard component level
We guarantee the reliability of oscillators by adopting JAXA certified parts and MIL certified parts (Space grade) whose reliability is guaranteed at the part level, or parts whose quality verification test is equivalent to MIL certified parts.
In particular, for radiation-resistant (SEE and TID) (*1), we use semiconductors with guaranteed radiation-resistance of a certain level or higher as semiconductor components, and for crystal unit, we use crystal blank cut from high-quality quartz raw stone, which is the same as JAXA certified crystal unit, which has a proven track record for space use.
As an oscillator, a radiation resistance test (TID) is conducted during the quality confirmation test to ensure quality.

(2) Oscillator Structure Considering Environmental Resistance Performances
A characteristic feature of required specifications for this oscillator is its wide range of operating temperatures. If the oscillator is repeatedly subjected to low and high temperatures, the solder may deteriorate due to heat stress on the part mount (soldering part). Some active parts are large in size and affected by heat stress. Electrical connections are made not by soldering, but by adhesive fixation and wire bonding.
Because of its small size, passive components are mounted with proven soldering for space use.
Crystal unit has a double-sealed structure that uses a packaged crystal unit to ensure the environmental resistance performance of crystal unit itself and improve performance of the oscillator. In addition, we have adopted a structure with a large number of terminals for the purpose of dispersing vibrations and shocks during launch.
The structure described above has proven to be a component for space use, and by adopting these components, quality in terms of structure has been secured. (Fig. 2)

Fig.2 Oscillator Structure Diagram

(3) Implement thorough process control (check and inspect each process)
As well as ISO9001 (Quality Management System), we have established a quality assurance program plan that conforms to the General Common Specifications (JAXA-QTS-2000) for common components for space development, and we control the quality of processes through reliable operation.

(4) Conducted quality verification tests for screening and Lot assurance
JAXA standard (JAXA-QTS-2020) conforming to MIL-STD-883 is applied.

a) Screening
In order to reject the initial defects, we conduct a full number of inspections for the items shown in Table 1.

Table 1 Screening

^(*2) 4 -digit number indicates MIL-STD-883 test procedure number.
^(*3) Stabilized bakes shall be conducted in-process inspections and omitted in screening.

b) Quality verification test for Lot assurance
To the sampling test for the items shown in Table 2 as a quality confirmation test to assure the quality at the lot level
We are doing this.

Table 2 Quality verification tests

^(*4)4 -digit number indicates MIL-STD-883 test method number.

As described above, we guarantee high reliability as oscillators for onborad satellites through quality control in parts, structure, process control, and assurance tests. As a result, we have been certified by the Japan Aerospace Exploration Agency (JAXA) as conforming to JAXA-QTS-2020 of common specifications for reliability assurance mixed integrated circuits for space development.

The external appearance of the oscillator for space is shown in Fig. 3, and the electrical characteristics are shown in Table 3.

Fig. 3 Space Oscillator Appearance (15.8 x 15. x 3.5 mm)

Table 3 Electrical performance

4. Summary
In the future, we will consider expanding the frequency and adding packages as required.
We will also apply the structure and quality control methods established in this design to highly reliable products in other markets.