PCB News - How to evaluate automotive HDI PCB manufacturers

The booming development of electronic industry has promoted the rapid development of many industries. In recent years, electronic products are widely used in automobile industry. The traditional automobile industry has put more effort into machinery, power, hydraulics and transmission. However, the modern automotive industry relies more on electronic applications, which are playing an increasingly important and potential role in automobiles. Automatic electrification is all about processing, sensing, information transmission and recording, which would not be possible without a printed circuit board (PCB). PCBS have been widely used in the automotive industry due to the requirements of automotive modernization and digitalization, as well as human requirements for vehicle safety, comfort, simple operation and digitalization. High density interconnect (HDI) PCBS may have cross layer blind holes or double layer structures.

In order to achieve high reliability and safety of automotive HDI PCB, HDI PCB manufacturers must follow strict policies and measures, which is the focus of this paper.

In automotive circuit boards, traditional single-layer PCB, double-layer PCB and multi-layer PCB can be used. In recent years, HDI PCB has been widely used in automotive electronic products. There is indeed a fundamental difference between regular AND automotive HDI PCBS: the former emphasizes practicality and versatility to serve consumer electronics, while the latter focuses on reliability, safety and high quality.

It is important to note that the regulations and measures discussed in this article are general rules and do not include those rules, since automobiles cover a wide variety of vehicles, such as cars, trucks or trucks, with different requirements for different performance expectations and functions. Special cases.

HDI PCB can be divided into single LAYER HDI PCB, double layer laminated PCB and three layer laminated PCB. In this context, the layer means the layer of the prepreg.

Automotive electronics are commonly used in two types of applications:

A. Automotive electronic controls, especially electronic fuel injection, anti-lock braking (ABS), anti-skid control (ASC), traction control, electronically controlled suspension (ECS), will not operate effectively until they are used in conjunction with the vehicle's mechanical systems (e.g. engine, chassis and vehicle digital controls). Electronic automatic transmission (EAT) and electronic power steering (EPS).

B. On-board automotive equipment that can be used independently in the automotive environment and is independent of vehicle performance includes automotive information systems or vehicle computers, GPS systems, automotive video systems, onboard communication systems and Internet device functions, which are implemented by HDI PCB-supported devices that are responsible for signal transmission and mass control.

Due to the high reliability and safety of automotive HDI printed circuit boards, automotive HDI PCB manufacturers must meet high-level requirements:

A. Automotive HDI PCB manufacturers must insist on integrated management systems and quality management systems that play a key role in judging or supporting the PCB manufacturer's management level. Certain systems cannot be owned by the PCB manufacturer until authenticated by a third party. For example, automotive PCB manufacturers must be ISO9001 and ISO/IATF16949 certified.

B.HDI PCB manufacturer must have solid technology and high HDI manufacturing capability. Specifically, manufacturers specializing in the manufacture of automotive circuit boards must manufacture circuit boards with a wire width/spacing of at least 75μm/75μm and a two-layer structure. It is recognized that HDI PCB manufacturers must have a process capability index (CPK) of at least 1.33 and a equipment manufacturing capability (CMK) of at least 1.67. No modification shall be made in subsequent manufacturing unless approved and confirmed by the customer.

C. Automotive HDI PCB manufacturers must follow the strictest rules when selecting PCB raw materials, as they play a key role in determining the reliability and performance of the final PCB.

Core plate and semi-cured sheet. They are the most basic and critical elements in the manufacture of automotive HDI PCBS. When it comes to raw materials for HDI PCBS, the core and prepreg are major considerations. In general, the HDI core plate and dielectric layer are relatively thin. Therefore, one layer of prepreg is sufficient for use on consumer HDI boards. However, automotive HDI PCBS must rely on the lamination of at least two layers of prepreg, as a single layer of prepreg can result in a reduction in insulation resistance if a cavity or binder deficiency occurs. After that, the end result could be a failure of the entire board or product.

? Membrane resistance welding. As a protective layer directly covering the surface circuit board, the solder resist plays the same important role as the core board and the prepreg. In addition to protecting external circuits, solder resisters also play a vital role in the appearance, quality and reliability of the product. Therefore, the solder resistance layer on the automotive circuit board must meet the most stringent requirements. Solder resist must pass a number of reliability tests, including heat storage tests and peel strength tests.

Qualified HDI PCB manufacturers never take material selection for granted. Instead, they had to run some tests on the reliability of the boards. The main reliability tests for automotive HDI PCB materials include CAF (conductive anode wire) test, high and low temperature thermal shock test, weather temperature cycle test and heat storage test.

CAF test. It is used to measure the insulation resistance between two conductors. The test covers many test values, such as minimum insulation resistance between layers, minimum insulation resistance between through holes, minimum insulation resistance between buried holes, minimum insulation resistance between blind holes, and minimum insulation resistance between parallel circuits.

High and low temperature thermal shock test. This test is designed to measure the rate of change of resistance which must be less than a certain percentage. Specifically, the parameters mentioned in this test include the resistance change rate between the through holes, the resistance change rate between the buried holes and the resistance change rate between the blind holes.

Climatic temperature cycle testing. The plate under test needs to be pretreated before reflow soldering. In the temperature range of -40 degree Celsius±3 degree Celsius to 140 degree Celsius±2 degree Celsius, the circuit board must be kept at the lowest and highest temperature for 15 minutes. As a result, qualified circuit boards do not laminate, white spot or explode.

High temperature storage test. The test is mainly aimed at the reliability of the solder resistance layer, especially its peel strength. This test is considered to be the most rigorous as far as welding resistance is concerned.

According to the testing requirements described above, potential risks may occur if the base material or raw material does not meet customer requirements. Therefore, whether or not the material is tested may be a key factor in determining a qualified HDI PCB manufacturer.

A number of strategies and measures can be used to identify automotive HDI PCB manufacturers, including certification of material suppliers, determination of technical conditions and parameters in the process, and application of accessories. They can be an important component in the search for reliable HDI PCB manufacturers. Determine and judge its reliability as a reference.