In the 1980s, the second-generation memory packaging technology TSOP appeared and was widely recognized by the industry. It is still the mainstream technology for memory packaging today. TSOP is the abbreviation of "Thin Small Outline Package", which means thin small size package. TSOP memory has pins made around the chip and is directly attached to the surface of the PCB board using SMT technology (surface mounting technology). When the TSOP package size is used, the parasitic parameters (output voltage disturbance caused when the current changes significantly) are reduced, which is suitable for high-frequency applications, is easier to operate, and has higher reliability. At the same time, TSOP packaging has the advantages of high yield and low price, so it has been widely used.
In the TSOP packaging method, the memory chip is welded to the PCB board through the chip pins. The contact area between the solder joints and the PCB board is small, making it relatively difficult to transfer heat from the chip to the PCB. Moreover, TSOP packaged memory will produce greater signal interference and electromagnetic interference after exceeding 150MHz. With the advancement of technology in the 1990s, chip integration continued to increase, the number of I/O pins increased dramatically, power consumption also increased, and the requirements for integrated circuit packaging became more stringent. In order to meet the needs of development, BGA packaging began to be used in production. BGA is the abbreviation of English Ball Grid Array Package, that is, ball grid array package.
Memory packaged with BGA technology can increase the memory capacity by two to three times while maintaining the same volume. Compared with TSOP, BGA has a smaller size, better heat dissipation performance and electrical properties. BGA packaging technology has greatly improved the storage capacity per square inch. Memory products using BGA packaging technology are only one-third of the size of TSOP packaging at the same capacity. In addition, compared with traditional TSOP packaging, BGA packaging The method has a faster and more effective way to dissipate heat.
The I/O terminals of the BGA package are distributed under the package in the form of circular or columnar solder joints in an array. The advantage of BGA technology is that although the number of I/O pins has increased, the pin spacing has not. The reduction has increased, thus improving the assembly yield; although its power consumption has increased, BGA can be welded with a controlled collapse chip method, which can improve its electrothermal performance; the thickness and weight are both higher than previous packaging technologies. Reduce; the parasitic parameters are reduced, the signal transmission delay is small, and the frequency of use is greatly increased; the assembly can be welded on the front surface, and the reliability is high.
When it comes to BGA packaging, we must mention Kingmax’s patented TinyBGA technology. TinyBGA’s full name in English is Tiny Ball Grid Array (small ball grid array packaging). It is a branch of BGA packaging technology and is owned by Kingmax. Successfully developed in August 1998, the ratio of its chip area to package area is not less than 1:1.14, which can increase the memory capacity by 2 to 3 times while maintaining the same volume. Compared with TSOP package products, it has Smaller size, better heat dissipation performance and electrical performance.
Memory products using TinyBGA packaging technology are only 1/3 of TSOP packaging with the same capacity. The pins of TSOP packaged memory are led from the periphery of the chip, while the pins of TinyBGA are led from the center of the chip. This method effectively shortens the signal transmission distance. The length of the signal transmission line is only 1/4 of the traditional TSOP technology, so the signal attenuation is also reduced. This not only greatly improves the anti-interference and anti-noise performance of the chip, but also improves the electrical performance. Chips using TinyBGA packaging can withstand FSBs up to 300MHz, while traditional TSOP packaging technology can only withstand FSBs up to 150MHz.
TinyBGA packaged memory is also thinner (package height is less than 0.8mm), and the effective heat dissipation path from the metal substrate to the heat sink is only 0.36mm. Therefore, TinyBGA memory has higher heat conduction efficiency, is very suitable for systems that run for a long time, and has excellent stability. CSP (Chip Scale Package) means chip-scale packaging. CSP packaging is the latest generation of memory chip packaging technology, and its technical performance has been further improved.
CSP packaging can make the ratio of chip area to package area exceed 1:1.14, which is very close to the ideal situation of 1:1. The absolute size is only 32 square millimeters, which is about 1/3 of an ordinary BGA and is only equivalent to TSOP memory. 1/6 of the chip area. Compared with BGA packaging, CSP packaging can triple the storage capacity in the same space.
CSP packaged memory is not only small in size, but also thinner. The most effective heat dissipation path from the metal substrate to the heat sink is only 0.2 mm, which greatly improves the reliability of the memory chip after long-term operation. The impedance is significantly reduced and the chip speed is greatly increased.
The center pin form of the CSP packaged memory chip effectively shortens the signal transmission distance, and its attenuation is reduced accordingly. The anti-interference and anti-noise performance of the chip can also be greatly improved, which also makes the CSP The access time is improved by 15%-20% compared with BGA. In the CSP packaging method, the memory particles are soldered to the PCB board through solder balls. Since the contact area between the solder joints and the PCB board is large, the heat generated by the memory chip during operation can be easily conducted to the PCB. board and spread out. The CSP package can dissipate heat from the back and has good thermal efficiency. The thermal resistance of CSP is 35℃/W, while the thermal resistance of TSOP is 40℃/W. WLCSP (Wafer Level Chip Scale Package), this technology is different from the traditional method of cutting the wafer first and then packaging and testing. Instead, it first packages and tests the entire wafer and then cuts it. . WLCSP has more obvious advantages. First, the process procedures are greatly optimized. The wafers directly enter the packaging process, while the traditional process requires cutting and classifying the wafers before packaging. All integrated circuits are packaged at once, marking work is performed directly on the wafer, and equipment testing is completed at once, which is unimaginable in traditional processes. Secondly, the production cycle and cost have been significantly reduced, and the production cycle of WLCSP has been shortened to one and a half days. Moreover, the new process brings excellent performance, and the use of WLCSP packaging technology reduces the number of pins required for the chip and improves integration. Another advantage brought by WLCSP is the improvement of electrical performance, and the electromagnetic interference generated by the pins is almost eliminated. Memory packaged in WLCSP can support a frequency of 800MHz and a maximum capacity of 1GB!