Breakthrough application of high-density SIP system level packaging technology in the field of bank card fingerprint key chips

This case demonstrates the significant breakthrough of high-density SIP (System in Package) technology in the field of financial payment security. Through innovative heterogeneous integration packaging technology, the four core functional chips of fingerprint sensor chip, security chip, control chip, and boost chip have been successfully integrated and packaged in a single chip with a thickness of only 0.35mm. The project team has overcome multiple technical challenges such as multi chip stacking, signal integrity, and low-power design in ultra-thin packaging, and innovatively adopted IO port conversion design and top mounted copper pillar connection scheme, perfectly meeting the strict requirements of bank cards for ultra-thin size, low-power operation, and high security. This product has passed strict certification by the three major international card organizations, Master card, Visa, and Amex, and has achieved large-scale commercial use. It has become one of the few suppliers in the world that can provide ultra-thin fingerprint bank card chip packaging solutions that meet international standards, providing solid technical support for the upgrading and replacement of financial payment security technology.

1、 Project Background

With the rapid development of mobile payment and biometric technology, traditional password payment methods are gradually showing limitations in terms of security and convenience. Fingerprint recognition, as a mature and secure biometric recognition technology, is widely regarded as the core authentication method for the next generation of financial payments. However, integrating fingerprint recognition functionality into standard thickness bank cards faces significant technological challenges.

The thickness of a standard bank card is only 0.76mm, leaving extremely limited space for chips and packaging. The traditional single-chip packaging solution cannot simultaneously accommodate multiple functions such as fingerprint acquisition, data processing, secure encryption, and power management, while the multi chip discrete solution will result in an overall thickness exceeding the standard and unable to meet the physical specifications of bank cards. In addition, bank cards have extremely strict requirements for power consumption, and the chip must be able to operate stably under limited power supply, while also ensuring extremely high security to prevent user fingerprint information and transaction data from being stolen or tampered with.

In this context, the market urgently needs an advanced packaging technology solution that can achieve multi chip integration, low-power operation, and high security assurance in ultra-thin spaces. This project is aimed at meeting this market demand, relying on self-developed high-density SIP system level packaging technology, and successfully developing an ultra-thin fingerprint key chip packaging product suitable for fingerprint bank cards.

2、 Core technology challenges

During the project development process, the team faces the following three core technical challenges:

Ultra thin multi chip integration challenge: It is necessary to integrate four chips with different processes, sizes, and functions into a package with a thickness of no more than 0.35mm, which puts unprecedented demands on the accuracy and reliability of the packaging process. Traditional wire bonding and flip chip bonding techniques cannot achieve reliable connection of multiple chips in such a thin space, and are prone to stress concentration and warping issues.

Signal integrity and electromagnetic interference challenges: High density integration of multiple chips in a small space can exacerbate crosstalk and electromagnetic interference problems between signals, affecting the normal operation of chips and the accuracy of data transmission. Especially the high-speed data transmission between security chips and fingerprint sensor chips requires extremely high signal integrity.

Low power consumption and connection challenges: Bank cards use passive power supply, and the chip must operate at extremely low power consumption. Meanwhile, the traditional bottom pin connection method increases the overall thickness and is not conducive to integration with bank card antennas, requiring the development of a new connection solution.

3、 Innovative solutions

In response to the above technical challenges, the project team has adopted a series of innovative technological means and successfully overcome various difficulties:

Heterogeneous Integration Packaging Technology: Advanced 2.5D/3D heterogeneous integration packaging technology is adopted to stack and integrate fingerprint sensor chips, security chips, control chips, and boost chips according to the optimal spatial layout. Through precise chip thinning technology, the thickness of each chip is reduced to below 50 μ m, and high-precision chip bonding processes are used to ensure alignment accuracy between multiple chips within ± 1 μ m. The team has also developed specialized low stress packaging materials and processes, effectively solving the warping and reliability issues of ultra-thin packaging bodies.

IO port conversion design: Innovatively designed a dedicated IO port conversion circuit to uniformly plan and manage the input and output interfaces of each chip. By reusing IO ports and optimizing signal routing, the number of interconnections between chips has been significantly reduced, reducing signal crosstalk and electromagnetic interference. At the same time, packaging wiring has been simplified, and packaging density has been improved. This design also implements power management and power consumption control between various chips, ensuring stable operation of the entire system in low-power mode.

Top mounted copper pillar connection scheme: abandons the traditional bottom pin connection method and adopts top mounted copper pillar technology to place all external connection points on the top of the package. Through high-precision electroplating technology, a highly consistent and highly conductive copper pillar array is formed on the top of the package, which is directly connected to the antenna and circuit layer of the bank card. This connection method not only significantly reduces the overall packaging thickness, but also improves the reliability and conductivity of the connection, while also facilitating subsequent bank card manufacturing processes.

4、 Core advantages of the product

The high-density SIP system level encapsulated fingerprint key chip developed in this project has the following significant advantages:

Ultra slim design: With an overall packaging thickness of only 0.35mm, it is currently one of the thinnest fingerprint bank card chips in the world. This thickness fully meets the total thickness requirement of 0.76mm for standard bank cards, leaving sufficient space for other functional modules of the bank card.

Highly integrated: Four core functional chips are integrated into one, achieving full functional integration of fingerprint acquisition, data processing, security encryption, and power management. Compared to traditional multi chip discrete solutions, the volume has been reduced by over 70% and the weight has been reduced by over 60%.

Ultra low power consumption operation: Through optimized power management design and low-power circuit design, the standby power consumption of the chip is less than 1 μ A, and the working power consumption is less than 5mA. With passive power supply from bank cards, it can stably complete the entire process of fingerprint recognition and transaction authentication without the need for additional power supply.

High security guarantee: Integrated with internationally certified dedicated security chips, hardware encryption technology is used to encrypt user fingerprint information and transaction data throughout the entire process. Fingerprint information is only stored in a secure area inside the chip and will not be read or copied externally, effectively preventing information leakage and fraudulent transactions.

High reliability: Passed strict environmental reliability tests, including high and low temperature cycling tests, wet heat tests, mechanical impact tests, and bending tests. The product can operate normally within a temperature range of -40 ℃ to+85 ℃ and can withstand various mechanical stresses and environmental impacts during daily use of bank cards.

5、 Commercial landing results

With excellent technical performance and reliable product quality, this product has obtained comprehensive certification from the three major international card organizations, Master card, Visa, and Amex, and has established deep partnerships with many well-known banks and card manufacturers worldwide, achieving large-scale commercial use.

As of now, fingerprint bank cards using this packaging technology have been issued in over 30 countries and regions worldwide, with a cumulative issuance of over 50 million cards. The product has demonstrated extremely high stability and reliability in practical applications, with a good user experience and a transaction success rate of over 99.9%, receiving unanimous praise from banks, card organizations, and end users.

The successful commercialization of this product not only breaks the monopoly of foreign companies in the high-end financial chip packaging field, but also promotes the application and development of semiconductor packaging technology in the financial security field in China, enhancing China's competitiveness in the global financial payment industry chain.

6、 Industry Value and Future Prospects

The successful implementation of this project fully demonstrates the enormous advantages of high-density SIP system level packaging technology in solving multi chip integration, ultra-thin packaging, and low-power design, opening up new directions for the development of semiconductor packaging technology. This technology is not only suitable for the financial payment field, but can also be widely applied in fields such as smart wearables, the Internet of Things, and automotive electronics that have strict requirements for size, power consumption, and integration.

In the future, we will continue to increase our research and development investment in high-density SIP system level packaging technology, continuously improve our process level and integration capabilities, and develop more advanced packaging products that meet market demand. We will further deepen cooperation with financial institutions, chip design companies, and terminal manufacturers, promote the application of fingerprint recognition technology in more financial payment scenarios, and contribute to building a more secure, convenient, and intelligent financial payment ecosystem. At the same time, we will actively explore the application of heterogeneous integration technology in emerging fields such as artificial intelligence and 5G communication, to help China's semiconductor industry achieve high-quality development.