자동차 HDI PCB 분류 및 응용

게시일 : 2020-02-17

The rapid development of the electronics industry has promoted the rapid development of many industries. In recent years, electronic products have become more and more widely used in the automotive industry. The traditional automotive industry is working harder on mechanics, power, hydraulics, and transmission. However, the modern automotive industry relies more on electronic applications that play an increasingly important and potential role in automobiles. Automatic electrification is all used for processing, sensing, information transmission and recording, which is never possible with a printed circuit board (PCB). Due to the demands of automobile modernization and digitization, and people’s requirements for automobile safety, comfort, simple operation, and digitization, PCBs have been widely used in the automotive industry, from ordinary single-layer PCBs, double-layer PCBs to complex multi-layer PCBs. -Layer PCB or high-density interconnect (HDI) PCB, possibly with cross-layer blind vias or two-layer build-up layers.

Automotive PCB Type

In automotive circuit boards, traditional single-layer PCBs, double-layer PCBs, and multilayer PCBs are available. In recent years, the widespread application of HDI PCBs has become the first choice for automotive electronics. There is indeed an essential difference between ordinary HDI PCBs and automotive HDI PCBs: the former emphasizes practicality and versatility to provide services for consumer electronics, while the latter strives for reliability, safety and high quality.

It is necessary to explain that because cars cover a wide range of vehicles such as cars, trucks, or trucks, and require different performance expectations and functions, the rules and measures discussed in this article are just some of the general applications other than these special cases rule.

자동차 HDI PCB 분류 및 응용

HDI PCB can be divided into single-layer HDI PCB, double-layer construction PCB and three-layer laminated PCB. Here, the layer refers to a prepreg layer.

Automotive electronics are generally divided into two categories:
a. Automotive electronic controls do not work effectively before cooperating with mechanical systems on the vehicle (such as engine, chassis and vehicle digital controls), especially electronic fuel injection systems, anti-lock braking systems (ABS), anti-skid controls (ASC) Traction control, electronically controlled suspension (ECS), electronic automatic transmission (EAT), and electronic power steering (EPS).
b. Vehicle-mounted automotive equipment that can be used independently in the automotive environment and has nothing to do with vehicle performance, including automotive information systems or automotive computers, GPS systems, automotive video systems, automotive communication systems, and Internet equipment. Functions are implemented by equipment supported by the HDI PCB, responsible for signal transmission and multi- Kind of control.

Requirements for automotive HDI PCB manufacturers

Due to the high reliability and safety of automotive HDI PCBs, automotive HDI PCB manufacturers must meet high-level requirements:
a. Automotive HDI PCB manufacturers must adhere to comprehensive management systems and quality management systems that play a key role in determining or supporting the management level of PCB manufacturers. Some systems cannot be owned by a PCB manufacturer until identified by a third-party certification. For example, automotive PCB manufacturers must pass ISO9001 and ISO / TS16949 certification.
b. HDI PCB manufacturers must be equipped with rugged technology and high HDI manufacturing capabilities. Specifically, a manufacturer specializing in the manufacture of automotive circuit boards must manufacture boards with a line width / space of at least 75 μm / 75 μm and stacked in two layers. It is generally believed that HDI PCB manufacturers must have a process capability index (CPK) of at least 1.33 and a device manufacturing capability (CMK) of at least 1.67. Modifications are not allowed in future manufacturing unless approved and confirmed by the customer.
c. Automotive HDI PCB manufacturers must adhere to the strictest rules for selecting PCB raw materials because they play a key role in determining the reliability and performance of the final PCB.

Material requirements for Automotive HDI PCB

• Core board and prepreg. They are the most basic and critical factors for manufacturing automotive HDI PCBs. When it comes to HDI PCB raw materials, the core board and prepreg are the main considerations. HDI core boards and dielectric layers are generally relatively thin. Therefore, one layer of prepreg is sufficient for consumer HDI boards. However, automotive HDI PCBs must rely on the lamination of at least two layers of prepreg, because a single layer of prepreg may cause a reduction in insulation resistance if cavities or insufficient adhesives occur. After that, the end result could be a failure of the entire board or product.

• Welding mask. As a protective layer directly covering the surface circuit board, the solder mask also plays an important role as the core board and prepreg. In addition to protecting external circuits, solder masks also play a vital role in product appearance, quality, and reliability. As a result, solder masks for circuit boards used in automobiles must meet the most stringent requirements. The solder mask must pass multiple reliability tests, including thermal storage tests and peel strength tests.

About Automotive HDI PCB Material Reliability Test

Qualified HDI PCB manufacturers never take material selection for granted. Instead, they must perform some tests on the reliability of the board. The main tests on the reliability of automotive HDI PCB materials include CAF (Conductive Anode Wire) tests, high and low temperature thermal shock tests, weather temperature cycle tests and thermal storage tests.

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

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

• Weather temperature cycling test. The boards to be tested need to be pre-treated before reflow soldering. In the temperature range of -40 ° C ± 3 ° C to 140 ° C ± 2 ° C, the circuit board must be kept at the minimum temperature and the maximum temperature for 15 minutes. Therefore, qualified circuit boards do not undergo lamination, white spots, or explosions.

• Thermal storage test. This test is mainly used for the reliability of the solder resist film, especially its peel strength. This test can be considered the most rigorous in terms of solder mask judgement.

According to the requirements of the above tests, if the substrate materials or raw materials cannot be met, there will be some potential risks to the needs of customers. Therefore, whether to test the material may be a key factor in determining a qualified HDI PCB manufacturer.

There are many strategies and measures that can be used to judge automotive HDI PCB manufacturers, including material supplier certification, technical conditions and parameter determination in the process, and application of accessories. Finding a reliable HDI PCB manufacturer can be an important factor in determining and judging its reliability.