At present, PCB products have begun to move from traditional to higher-density HDI/BUM boards, IC packaging base (carrier) boards, embedded component boards and rigid-flex boards, and PCBs will eventually reach the limit of “printed circuit boards“. Ultimately, it will inevitably lead to a “qualitative change” from “electrical transmission signal” to “optical transmission signal”, replacing printed circuit boards with printed optical circuit boards.
Due to the rapid development of the miniaturization, high performance, multi-function and high frequency (speed) of signal transmission of electronic products, the PCB must quickly move from the traditional PCB industry to the products characterized by high density and refinement. PCB products have begun, partially or fully moved towards high-density interconnect laminate (HDI/BUM) boards, package base (carrier) boards, integrated (embedded) component printed boards (ICCB) and rigid-flex printed boards board (G-FPCB). In the next period of time, these four types of PCB products will definitely become the four major highlights of the PCB industry, and in the future, more advanced printed optical circuit boards that transmit and calculate with “optical signals” will also replace the current “electrical signals”. Printed circuit boards for transmission and computing.
The output value of HDI/BUM board with core board accounts for 95%.
HDI/BUM board is a type of PCB with higher density than conventional printed boards. It can be divided into two types, that is HDI/BUM board with “core board” and without “core board”.
The HDI/BUM board with “core board” is a PCB formed by several higher-density interconnect “layers” on one or both sides of the “conventional printed board”. In fact, HDI/BUM boards with core boards are a structural form of “transition” from “conventional printed boards” to higher-density PCBs to meet the requirements of very high-density installations. At the same time, no matter from equipment, process technology and management, it can also better adapt to the best method of transition from the original PCB industry to very high density PCB products. If a slight improvement can be made on the basis of the existing PCB production equipment, testing and technology, development and production can be carried out, with low investment, low cost, and good continuity and scalability in management and production, so it is widely used. Accepted by most PCB manufacturers, therefore, HDI/BUM boards with core boards account for about 95% of the current output value of HDI/BUM boards.
For HDI/BUM boards with core boards, the increase in high density is significant and outstanding. For example, 200×300cm2 HDI/BUM boards using 4+12+4, compared to 400×450cm2 46-layer buried/blind via high-rise boards, have higher capacity, better electrical performance and reliability and longevity.
At present, most of the HDI/BUM boards without “core board” use conductive adhesive technology, and their scope of use is limited, so the proportion is very small.
IC packaging substrate is the most important to solve the problem of CTE matching.
IC packaging substrates are developed on the basis of HDI/BUM boards by continuing to “deepen (high density)”, or IC packaging substrates are HDI/BUM boards with higher density. In essence, the primary problem of the IC packaging substrate is the compatibility problem with the CTE (coefficient of thermal expansion) of the components to be packaged (components), and the second is the problem of high density.
Essentially, PCBs provide interconnection and mechanical (physical) support for elements (components). In today’s electronic packaging market, there are mainly three types of packaging: (1) organic substrate packaging; (2) ceramic substrate packaging; (3) ideal size and speed (ie chip level) packaging, such as crystal Wafer Level Package (WLP, Wafer Level Package), Direct Die Attach (DDA). Obviously, conventional PCBs do not have these advanced packaging (low CTE occasions) capabilities. Therefore, the PCB industry must develop technologies and products that can perform these advanced packaging substrate materials.
The problem of CTE compatibility between the package substrate and the package element (component). When the CTEs of the two do not match or differ greatly, the internal stress generated after soldering the package threatens the reliability and life of electronic products. Therefore, the problem of CTE compatibility between the package substrate and the packaged components requires that the difference in CTE between the two is getting smaller and smaller as the mounting density increases and the solder joint area shrinks.
IC packaging substrates are mainly reflected in the following aspects. 1. The CTE of the substrate material is smaller or matched, that is, the CTE of such IC substrates must be significantly reduced and close to (compatible with) the CTE of the chip pins to ensure reliability. 2. Directly used for the packaging of bare chips (KGD), the IC substrate is required to be denser. 3. The thickness of the packaging substrate is thin and the size is small, most of which are less than 70mm × 70mm. 4. Most of the low-CTE substrates are used, such as PI material, ultra-thin glass fiber cloth and CCL material of carbon fiber.
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