① Flip-chip method and wire bonding method: It is a direct mounting method with small mounting area, but the chip cannot be predicted (aging screening), which affects the qualification rate and reliability of hybrid circuits or microelectronic assembly components.
(2) Chip carrier method: This is a predictable packaging type of microchips, with more than 300 microchips with pads (or leads) on the four sides and bottom. There are many structural types of carriers (Figure 1). Lead sealed carrier with tower radiator and 4-chip carrier. The sealed ceramic carrier has high reliability and wide application, and its area is about 1/4 ~ 1/20 of that of the dual in-line housing (Figure 2).
③ Carrier tape method: a special flexible printed circuit for chip installation, interconnection and prediction, which looks like a film. It is characterized by a high degree of production automation. Modern technology includes automatic welding of carrier tape and automatic welding of bump carrier tape. Include thick film hybrid circuits, thin film hybrid circuits and microwave integrated circuits.
① The sealed carrier-multilayer thin wire substrate module is a module adopting high-density interconnection and assembly technology. The advantage of this module is that it can use various substrates (such as ceramic substrates, glazed steel substrates, printed circuit boards and phenolic cardboard, etc.). ); The sensitive chip can be packaged in a sealed carrier, and the components do not need a large packaging shell, so the volume and weight are much smaller than those of the hybrid circuit; Good manufacturability, debugging and maintainability; Good heat dissipation; The carrier can be mounted on both sides of the substrate by vapor remelting welding technology, which improves the assembly density.
② Multilayer ceramic substrate is the most widely used substrate in modern times. Generally, the line width of thick film conductor printed by screen printing is 0. 1 ~ 0.2 mm, and the grid spacing of wiring is 0.25 ~ 0.5 mm Its manufacturing methods include dry method and wet method. Generally, the number of layers of dry wiring does not exceed 10, and the number of layers of wet wiring can reach 33, but its manufacturing process is more complicated than dry wiring. More than 100 chips (carriers and tapes) can be assembled on a substrate, and its function is equivalent to an extension, subsystem or even the whole machine of conventional electronic assembly. In this way, the assembly level and the number of external interconnection points are greatly reduced. Printed circuit board components of digital circuits or analog circuits can be assembled by chip (carrier, carrier tape)-substrate assembly, and its volume and weight can be reduced to one-fifth to one-tenth of the original.
Surface mount technology of thin-line printed board is also a new microelectronic assembly method.
③ Organic polymer thick film circuit is an organic polymer thick film circuit printed on phenolic cardboard, epoxy glass fiber cloth and other substrates. Can be assembled and welded with chips, carriers and carrier tapes, and has the characteristics of low curing temperature and low price.
④ The interconnection wiring density of organic thin film multilayer thin film circuit is higher than that of thick film circuit, and the wiring grid can reach 0. 1mm or even smaller.
⑤ Microwave components include monolithic microwave integrated circuits and microwave power amplifier components. The former is to fabricate microwave transistors and microwave integrated circuits on very small GaAs substrates; The latter is to assemble a microwave transistor carrier on a microwave integrated circuit with an alumina substrate. The output power of L-band is 100W, which can make the transmitter solid and compact, and has been used in phased array radar.
The heat conduction module of IBM308 1 processor is a new type of microelectronic module. Using 28 ~ 33 layers of wet wiring, 1 18 large-scale integrated high-speed bipolar logic circuit chips and gate array chips are mounted on a 90×90 mm ceramic substrate. Each chip has more than 120 pads arranged in a grid matrix of 0.25 × 0.25mm. The module * * * contains 350,000 through holes, and the thinnest film conductor is 0.08mm. Its production, testing and debugging processes are all controlled by computer. The input and output are 1800 pin array leads, which are interconnected with a large 20-layer thin-line printed board (600×700 mm) through a socket with zero insertion force. When the power consumption reaches 300 watts, heat dissipation measures such as heat conduction, water cooling and helium filling are adopted to keep the junction temperature of all chips. Later, Japan and the United States successfully developed micro-gap heat conduction and air-cooled heat dissipation modules, which made the module structure simpler and lighter. From the late 1970s to the early 1980s, higher density microelectronic assembly products were used in airborne, missile-borne and shipborne electronic equipment. For example, an airborne computer consists of 8 sealed carriers-multilayer ceramic substrates 108× 150 mm, with a volume of only 30×160× 230 mm. IBM's 438 1 computer adopts 22 micro-gap heat conduction air-cooled modules (each module size is 64×) Only one printed circuit board is used to complete the function of the central processing unit, which can be completed by the cabinet with traditional electronic components. NEC's SX-2 supercomputer adopts advanced high-speed large-scale integrated chips and high-speed high-density microelectronic assembly technology, achieving a machine cycle of 6 nanoseconds and a floating-point operation speed of 65.438+0.3 billion times per second.
Heat dissipation and cooling technology
One of the key technologies of microelectronic assembly. Because of its small size, high circuit density and high power density, the maximum power of the new single chip is 12 watt, and the power density of the module is 4 watt/cm2. Therefore, effective cooling methods must be adopted. In addition to air cooling with radiator, there are cold plate, liquid cooling, heat pipe and boiling cooling.
Micro connector
It has the advantages of small volume, many pins, reliable contact and zero or very low plug-in force.
Microelectronic component design
Problems such as circuit division, assembly structure, wiring design, signal transmission delay, influence of distributed parameters, impedance matching, crosstalk suppression, voltage drop of power supply and grounding system, * * coupling, decoupling, shielding and heat dissipation must be considered in the design.
Microelectronic assembly process
It mainly includes fine substrate manufacturing, chip installation, welding, aging test, packaging and circuit debugging.
The use of large-scale, ultra-large-scale and ultra-high-speed integrated circuits needs to be combined with advanced assembly technology to manufacture advanced electronic equipment. Modern electronic equipment needs more and more microelectronic components. The new technologies of microelectronic assembly under study include multi-substrate high-density stacked components, new multi-layer thin-wire substrate technology, heat dissipation technology, solderless micro-interconnection technology, and microelectronic assembly technology combining sound and photoelectricity.