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Automotive PCB Requirements, Performance Properties and Features

Automotive PCB Requirements, Performance Properties and Features

Introduction:

A large part of the automotive industry consists of electronic components. Car cockpits are being fitted with sensors and processors along with around 200 various electronic control units. They are used in the automotive body, chassis, power system, and dynamical system. However, there are a number of requirements which must be met by the PCBs used in automobiles.

Requirements for Automotive PCBs:

1: Quality Assurance:

For quality assurance manufacturers use a sound quality management system i.e. ISO9001. Another quality management system was established in 1994, the QS9000. And the beginning of the 21st century brought a new quality management system based on the ISO9001 and called the ISO/TS16949. This integrates special requirements for the automotive industry and focuses on producing quality automobiles while reducing waste and defects. Therefore automotive are usually ISO/TS16949 certified prior to their introduction in the market.

2: Performance Requirement:

  • High reliability: There are two aspects to automotive reliability: service life and environmental resistance. The service life of most automotive is from 10-12 years during which only parts can be replaced. And if we talk about environmental resistance it is the amount of resistance the PCB, automotive or electronic system shows to severe environmental conditions such as humidity, cold, heat, rain, EMI, etc.
  • Lightweight and miniaturization: Lightweight and miniaturization of components help to reduce the volume and save fuel. In the beginning of the 21st century, the volume of automotive-applied ECU (Electronic Control Unit) was around 1200cm3which has now been reduced to nearly one-quarter of its former size.

Automotive PCB Requirements, Performance Properties and Features 4

Automotive PCBs Performance Properties:

1: Multiple Types

The type of PCB used for a particular component is different depending on the application and function. Depending on the type of substrate material used they may be inorganic ceramic-based PCBs or organic resin-based PCBs. Ceramic-based PCBs are heat resistive and show dimensional stability, perfect for engine systems used in a high-temperature environment. They are however expensive and show bad manufacturability. Nowadays resin-based PCBs are being used in the majority of automobiles, they also show heat resistance. Generally, we can classify the vehicle device with the type of PCB suitable for use as follows.

  • Speedometer; air conditioner: Single/double-layer PCB (may be flexible PCB)
  • Car stereo; monitor: Double/Multi-layer PCB. Flexible PCB
  • Automotive communication devices; wireless location appliances; security control system: Multi-layer PCB. Flexible PCB. HDI PCB.
  • Engine system; power transmission control system: Metal-core PCB. Rigid-flex PCB
  • Vehicle power controller; navigation device: Embedded PCB

2: PCB Reliability Requirements for Different Sections of a Vehicle

Automotives tend to consist of components with high reliability. There are a number of tests which are implements on the electronics used in automobiles. We will discuss three of them here.



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  • TCT (Thermal Cycling Test): The different sections of a vehicle are subject to the following thermal cycling temperatures depending on five levels
    • A: Within Vehicle Body: -40°C to 85°C
    • B: Vehicle chassis below: -40°C to 125°C
    • C: Above engine: -40°C to 145°C
    • D: Transmission parts: -40°C to 155°C
    • E: Within engine: -40°C to 165°C

 

  • TST (Thermal Shock Test): High heat us something automotive PCBs will have to face and so they usually undergo a thermal shock test to ensure heat resistance. For this automotive PCBs are immersed in solder paste with a high temperature of around 260°C – 288°C for ten-second three times. The qualified PCBs will have no issues with lamination, have no bumps or copper cracks. Nowadays lead-free soldering is used with high soldering temperature which makes this test even more essential.
  • THB (Temperature-Humidity Bias) Test: Automotive PCBs have to face humid environments at times hence this test is important. This is also capable of inspecting PCB Conductive Anodic Filament (CAF) mobility. CAF occurs between adjacent bias on circuit board, adjacent vias, and wires or adjacent layers and wires. This may lead to shortcuts due to decreased insulative.

 Automotive PCB Requirements, Performance Properties and Features 5

Automotive PCB Manufacturing Features:

1: High-frequency PCBs

Radars incorporated in automotive require PCBs which transmit microwave high-frequency signals. In these cases, substrate materials with low dielectric loss are suggested. The substrate also consists of polytetrafluoroethylene (PTFE). This is different from the common FR-4 used. They also have different and distinct manufacturability.

2: Heavy copper PCBs

More advanced devices require more heat dissipation and larger current. In order to achieve this, the thickness of copper in PCB is increased. Heavy copper multi-layer PCBs are generally more difficult to fabricate than heavy copper double-layer PCBs. The inner circuit of heavy copper multi-layer PCB is heavy copper. The graphics transferring require a heavy film which shows resistance to corrosion. Similarly, the etching time is longer and the overall aim should be to ensure excellent quality of heavy copper circuits. In the case of generation of cavities in multi-layer PCB, then thin prepreg (containing a high amount of resin) is used.

3: Component embedment

Embedment technology is used in automotive electronics because it helps to increase assembly density and reduce the size of the product. There are many embedded PCB manufacturing options based on component embedment methods.  These include:

  • First, the groove is milled then the SMD (Surface Mount Device) is assembled through wave soldering or conductive paste.
  • Thin-film Surface Mount Devices (SMDs) are assembled on inner circuits by wave soldering.
  • Thick-film components are printed on a ceramic base.
  • SMDs are first assembled through wave-soldering then resin is used for packaging.

4: HDI (High-Density Interconnect) technology

Just as smartphones and tablets call for HDI PCBs, so do vehicles. They allow for communication and have functions of entertainment. Resultantly, microvia drilling, electroplating, and interconnection technologies are applied in automotive PCBs.


This article and associated images are provided by PCB Manufacturer PCBGOGO. You can contact them even for small order.

 

 


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