The packaging substrate can provide electrical connection, protection, support, heat dissipation, assembly and other functions for chips and electronic components to achieve multi-pin, reduce the size of packaged products, improve electrical performance and heat dissipation, ultra-high density or multi-chip Modular and high-reliability electronic substrate packaging substrates can be simply understood as PCBs or thin-thick film circuit substrates with higher performance or special functions. The packaging substrate serves as the electrical interconnection and transition between different circuits of the chip and conventional printed circuit boards (mostly motherboards, sub-boards, backplanes, etc.). It also provides protection, support, heat dissipation, assembly and other functions for the chip.
PWB and PCB
PWB (printed wiring board) generally refer to an insulating substrate with conductor patterns arranged on the surface and inside. PWB itself is a semi-finished product and functions as a substrate on which electronic components are mounted. Through conductor wiring, connections are made to form unit electronic circuits and perform their circuit functions.
PCB (printed circuit board) refers to the entire substrate of the PWB equipped with electrical components as a printed circuit board. In most cases, PWB and PCB are usually treated as synonyms without distinction. In fact, there are differences between PWB and PCB in some cases. For example, PCB sometimes refers to the simple printing method on an insulating substrate to form a circuit including electronic components, which can be self-contained; while PWB puts more emphasis on carrying components. The carrier function of the device may constitute an installed circuit or a printed circuit board assembly. The two are usually referred to as printed boards.
Motherboard: Also known as motherboard. It is an electronic substrate that installs various active and passive electronic components on a large-area PCB and can interconnect with sub-boards and other devices. The communications industry generally calls it a backplane.
The word “implementation” comes from Japanese and is borrowed here. The “block” mounted on the “board” is called mounting, and the bare chip is mounted on the module substrate. Sub-board: also called sub-board or component board, it is to install some electronic components on a smaller PCB to form a variety of Functional cards, storage components, CPU components and substrates with other components. Then the load and interconnection with the motherboard are realized through connectors (connectors, cables or rigid-flex boards, etc.). This makes it easier to repair faulty components and upgrade electronic products.
Real-time installation specifically refers to the connection process and process of mounting the above-mentioned “block” on the substrate, covering commonly used insertion, plug-in, surface mount (SMT), installation, micro-assembly, etc.
Module: The “board” that will be discussed below can be regarded as a multi-dimensional body. A package with lead terminals is a “block”, and a chip mounted on a bare chip can also be considered a block.
Carrier board Carrier board: A printed circuit board that carries various active and passive electronic devices, connectors, units, sub-boards and other various electronic devices. Such as package carrier boards, similar carrier boards, various ordinary PCBs and assembly boards.
Substrate Like-PCB (SLP): As the name suggests, it is a PCB with similar specifications to a carrier board. It is originally an HDI board, but its specifications are close to the level of a carrier board for IC packaging. Class carrier boards are still a type of PCB hard board, but the manufacturing process is closer to semiconductor specifications. Currently, the line width/line spacing required for class carrier boards is <30um/30um, which cannot be produced by the subtractive method and requires the use of MSAP (semi semi-conductor board). Additive method) process technology, which will replace the previous HDIPCB technology. It is a substrate material that integrates the functions of packaging substrate and carrier board. But the manufacturing process, raw materials and design (one piece or multiple pieces) have not yet been determined. The catalyst for carrier-like boards is Apple’s new mobile phone. In the 2017 iPhone 8, for the first time, a carrier-like HDI board produced with a process close to the IC was used, which can make the phone thinner, lighter and smaller. The base material of the carrier-like board is also similar to the carrier board for IC packaging, mainly a laminated dielectric film of CCL of BT resin and ABF* resin.
Multilayer board: With the improvement of LSI integration, the speed of signal transmission and the development of electronic equipment in the direction of light, thin and short, it is no longer sufficient to rely solely on single and double-sided conductor wiring. Furthermore, if the power line, ground line and signal line are Arrangement in the same conductor layer will be subject to many restrictions, thus greatly reducing the freedom of wiring. If the power layer, ground layer and signal layer are specially designed and arranged on the inner layer of the multi-layer board, it can not only improve the freedom of wiring but also prevent signal interference and electromagnetic wave radiation. This requirement further promotes the development of multi-layered substrates. Therefore, PCB integrates the key technologies of electronic packaging and plays an increasingly important role. It can be said that contemporary PCB is a master of various modern technologies.
HDI substrate HDI substrate: Generally manufactured using the build-up method. The more times the layers are built up, the higher the technical grade of the board. Ordinary HDI boards are basically one-time lamination, while high-end HDI uses two or more lamination technologies, as well as advanced PCB technologies such as stacked holes, electroplated hole filling, and laser direct drilling. High-end HDI boards are mainly used in 4G mobile phones, advanced digital cameras, IC carrier boards, etc.
In electronic packaging engineering, electronic substrates (PCBs) can be used at different levels of electronic packaging (mainly used for levels 2 to 5 of level 1 to level 3 packaging), but the packaging substrate is used for levels 2 and 3 of level 1 and level 2 packaging. , Ordinary PCB is used for levels 3, 4, and 5 of level 2 and 3 packaging. However, they all provide interconnection, protection, support, heat dissipation, assembly and other functions for electronic components to achieve multi-pin, reduce the size of packaged products, improve electrical performance and heat dissipation, ultra-high density or multi-chip modularization and For the purpose of high reliability
Main board (motherboard), secondary board and carrier board (class carrier) Conventional PCB (mostly motherboard, secondary board, backplane, etc.) are mainly used for levels 3, 4, and 5 of level 2 and 3 packaging. It is equipped with active devices, passive discrete devices and electronic components packaged such as LSI and IC, and performs its circuit function through interconnection to form unit electronic circuits.
With the continuous progress and development of electronic installation technology, the boundaries between various levels of electronic installation are becoming increasingly unclear. The intersection and integration of various levels of installation have made the role of PCB more and more important in this process. The role of PCB and its substrate materials in Higher and newer requirements have been put forward in terms of function and performance. The process and reasons for the separation of the packaging substrate from the PCB. After the 1980s, with the widespread application of new materials and new equipment, integrated circuit design and manufacturing technology followed the “Moore’s Law” “With rapid development, the advent of tiny and sensitive semiconductor components, the emergence of large-scale integrated circuit and very large-scale integrated circuit designs, and the emergence of high-density multi-layer packaging substrates have separated integrated circuit packaging substrates from ordinary printed circuit boards, forming Proprietary integrated circuit packaging substrate manufacturing technology.
At present, among the mainstream products of conventional PCB boards, products with line width/line spacing of 50um/50um are high-end PCB products, but this technology still cannot meet the technical requirements of current mainstream chip packaging. In the field of packaging substrate manufacturing, products with line width/line spacing of 25um/25um have become routine products. This reflects from the side that packaging substrate manufacturing is more technologically advanced than conventional PCB manufacturing. There are two fundamental reasons why the packaging substrate is separated from the conventional printed circuit board: on the one hand, because the refinement development speed of the PCB board is lower than the refinement development speed of the chip, the direct connection between the chip and the PCB board is difficult. On the other hand, the overall refinement of the PCB board increases the cost much higher than the cost of interconnecting the PCB and the chip through the packaging substrate.
Main structure and production technology of packaging substrate
At present, there is no unified classification standard in the packaging substrate industry. It is usually classified according to the substrate materials and manufacturing technology suitable for substrate manufacturing. According to different substrate materials, packaging substrates can be divided into inorganic packaging substrates and organic packaging substrates. Inorganic packaging substrates mainly include: ceramic-based packaging substrates and glass-based packaging substrates. Organic packaging substrates mainly include: phenolic packaging substrates, polycool packaging substrates and epoxy resin packaging substrates. According to different manufacturing methods of packaging substrates, packaging substrates can be divided into core packaging substrates and new coreless packaging substrates
Core and coreless packaging substrates
The core packaging substrate is mainly divided into two parts in structure, the middle part is the core board, and the upper and lower parts are the laminated boards. Core packaging substrate manufacturing technology is based on high-density interconnect (HDI) printed circuit board manufacturing technology and its improved technology.
Coreless substrate, also called coreless substrate, refers to the packaging substrate with the core board removed. The production of new coreless packaging substrates mainly uses bottom-up electrodeposition technology to produce interlayer conductive structures – copper pillars. It only uses an insulating layer (Build-up Layer) and a copper layer to achieve high-density wiring through a semi-additive process (SAP) build-up process.
Advantages and disadvantages of coreless packaging substrate
Advantage
Thin;
The electrical transmission path is reduced, the AC impedance is further reduced, and its signal line effectively avoids the return loss caused by PTH (copper plated through hole) on the traditional core substrate, which reduces the inductance of the power system loop and improves transmission. characteristics, especially frequency characteristics
Direct transmission of signals can be achieved because all line layers can be used as signal layers, which can improve the freedom of wiring, achieve high-density wiring, and reduce the limitations of C4 layout:
Except for part of the process, the original production equipment can be used, and the process steps are reduced.
Disadvantages
Without core board support, coreless substrates are prone to warping and deformation. This is currently the most common and biggest problem.
Laminate breakage is prone to occur
It is necessary to introduce some new equipment for semiconductor packaging coreless substrates. Therefore, the challenges of semiconductor packaging coreless substrates mainly lie in materials and processes.
