Brief Analysis of Vehicle Regulation Levels in In-Vehicle Displays

What is the automotive grade? What are the specific contents of the automotive grade standards? As a practitioner in the automotive display industry, I will briefly introduce it from this perspective.

Display products are distributed in various industries and have various specifications. At present, the general specification standards are military industry > automobile > industry > consumer electronics. Of course, industry is a very broad range, and only conventional industrial products are selected here for analogy.

If a company wants to enter the automotive field, make its products part of the car, and enter the supply chain of major Tier 1 suppliers, it must pass several extremely strict automotive specifications and standards in the world: first, the AEC-Q100 (IC), 101 (discrete components), and 200 (passive parts) reliability standards promoted by the North American automotive industry; second, it must comply with the zero-defect supply chain quality management standard ISO/TS 16949 specification (Quality Management System).

AEC-Q100 is a failure mechanism based on stress testing of packaged integrated circuits. The Automotive Electronics Council (AEC) is headquartered in the United States and was originally established by the three major automakers (Chrysler, Ford and General Motors) to establish common component qualification and quality system standards. This standard is more of an assessment of chips, and the quality standards are divided by temperature:

Level 0 -40℃ ~ +150℃

Level 1 -40℃ ~ +125℃

Level 2 -40℃ ~ +105℃

Level 3 -40℃ ~ +85℃

The core chip in the car needs to meet the level 0 standard. For the whole car display, it only needs to meet the level 3 standard, that is, the temperature range of -40 to 85.

In addition to the need for products to meet AEC standards, if a company itself needs to be recognized by a car manufacturer or Tier 1 manufacturer, they also need to pass a quality system requirement published by the International Organization for Standardization, which is what we often call TS16949. It was renamed IATF16949 in 2016. Its full name is "Quality Management System - Particular Requirements for the Organization and Implementation of ISO9001 for Production Parts and Related Service Parts in the Automotive Industry".

Before China started to manufacture cars on its own, the two major car manufacturing bases in the world: the United States and Europe, both had their own independent quality management standards. Among them, the three major automobile companies in the United States (GM, Ford, and Chrysler) jointly adopted QS-9000 as the unified quality management system standard for their suppliers since 1994, while the car companies in Germany and France, another production base in Europe, were using their own independent quality management systems, such as VDA6.1, AVSQ94, EAQF, etc., and the parts manufacturers of these car companies needed to meet the standards of both production bases at the same time, so the birth of IATF16949 came into being naturally.

The above briefly introduces some international standards and their differences. Next, from the perspective of the vehicle display unit, we will specifically introduce the technical specifications of a complete vehicle display screen set by the vehicle manufacturer and the whole machine manufacturer. First, let's take a look at the test level, which is generally divided into the following four levels:

A: Technical performance indicators are normal, no abnormalities

B: Performance degrades during the test but does not become abnormal, and recovers automatically after the test is completed

C: Lost during testing but recoverable after human intervention

R: Except for protection components, no irreversible loss of function or performance degradation due to equipment or software damage or data loss is allowed

The specifications of vehicle display components are generally as follows

1

Voltage

Standard voltage, the signal part is 3.3V, and the working voltage range is basically 2.7~3.6V.

2

Temperature requirements

The temperature here is divided into working temperature and storage temperature. Generally speaking, the working temperature definition range is: -30℃~﹢85℃; the storage temperature definition range is: -40℃~﹢90℃.

The above temperatures are usually accompanied by notes: when the relative humidity is between 25% and 75%, the product will have mechanical and electronic effects.

There should not be any abnormality in the work, no damage should be caused to the product itself, and the product should guarantee its performance.

3

Display surface temperature

Generally speaking, at room temperature, place the sample in a simulated actual vehicle loading state, power on and adjust the brightness to a certain value (usually 600~800cd/m²) for a period of time (usually 120min), and test it near the light bar. The surface temperature of the display screen is no higher than 45℃.

4

Optical requirements

In theory, optical requirements are not within the requirements of vehicle specifications. However, for vehicle display modules, optical requirements are the most important evaluation indicators, which include many items, each of which is different. Generally speaking, they include the following indicators:

Resolution, display area (AA area in the industry), display mode, brightness, contrast, aspect ratio, pixel size and shape, white screen uniformity, black screen uniformity, color saturation (color gamut), response time at different temperatures, viewing angle, color coordinates (including white, red, green, and blue), surface reflectivity, color cast, Mura, integrated black, etc.

Customers' demands for display screens will define different resolutions based on different sizes. The larger the size, the higher the resolution requirement. Customers will also customize other optical data based on application scenarios, their own cost requirements, and the requirements of terminal car manufacturers. As for central control products, since touch is involved, it is also necessary to work with touch and cover manufacturers to propose some hard indicators, such as the surface treatment of polarizers, bonding methods, frame requirements, integrated black, etc.

The above are some of the optical requirements for screen displays. A complete vehicle display module needs to combine various components such as panels, polarizers, backlight sources, etc. to finally show its shining side.

5

Electrical requirements

In addition to optics, electrical aspects must also meet customer requirements, which includes the backlight interface definition, power-on and power-off timing, etc.

6

Reliability requirements

A High and low temperature operation: Regarding reliability, the temperature mentioned above is mentioned again. Most screens are required to be able to work continuously for 500 hours under extreme high and low temperature conditions. Due to cost issues, customers may allow only 240 hours of testing for some products.

B High and low temperature storage: Storage is the most basic non-working state requirement, generally requiring operation at extreme temperatures for 500 hours.

C. Thermal shock resistance: Place the product in a test chamber without power supply and perform 400 cycles of thermal shock according to Table 6. After the test, place the product at room temperature for 2 hours and then perform appearance, mechanical structure and function inspections and main electrical performance tests. The following figure shows some requirements of a certain car manufacturer for thermal shock:

7

Mechanical environmental testing

Mechanical tests mainly include positive vibration, random vibration, transportation vibration, mechanical shock, packaging drop and other items, which mainly examine the stress performance of display components.

Positive rotation vibration: Install according to the installation angle of the product specification, power off, acceleration 5g, frequency range: 10HZ-60HZ-10HZ, power off, acceleration 5g, 3 axes, duration 20min per axis, scanning cycle 2min.

After the test, it shall comply with the requirements in 4.2 and 4.3 and the functional level shall meet Class A requirements.

Random vibration: The product is fixed on the vibration table according to the actual vehicle installation angle, 3Sigma limit, as shown below, the average acceleration is generally 3g, three axes, each axis vibrates for a certain time, generally 8 hours

Transport vibration: The sample is packaged, and a total of 2 packages are tested. The direction of the vibration table remains unchanged (Z axis), and only the direction of the package is changed. The sine vibration frequency is 10~15HZ, the acceleration is 1~5g, the amplitude peak is 8~10mm, and the vibration time is 15min per side. The three weakest sides (the sides with the most stitched edges) of the first package are tested, and the remaining three sides of the other package are tested. During the test, the package must be fixed tightly and the corner protection tape must be used to prevent damage to the package during the test.