Flip chip bonding process for base plate

Abstract

The invention relates to a flip chip bonding process for a large-deformation pre-pressed base plate. The process is characterized in that: firstly, a soldering flux is printed on the base plate; after the soldering flux is coated and a chip is aligned with the base plate, certain pre-pressure is applied to one side of a suction head at a chip end, so that salient points undergo large deformation under the pre-pressure and is tightly connected with a Cu soldering-pan on a PCB in a more effective mode; and the height of a welding spot is recovered under the effect of surface tension in a subsequent refluxing process. The interconnection rate between a high-density welding spot and a PCB base plate is greatly enhanced, basically to 100 percent, and reliable interconnection between the welding spot and the PCB base plate can also be realized even under the condition of poor coplanarity of array salient points or severe alignment error between the welding spot and the Cu soldering-pan. The process solves the problem of low conduction rate between the high-density salient points and the soldering-pan, and has the advantages of high welding intensity, good technical stability and high repeatability.

Description

technical field [0001] The invention relates to a substrate flip-chip welding process, more precisely relates to a substrate flip-chip welding process with large deformation and preloading, and belongs to the field of electronic packaging. Background technique [0002] The traditional flip-chip soldering process first prints flux on the substrate, and the flux plays a role in fixing the chip on the pad position before reflow, and plays a role in reducing oxidation during reflow. After the flux is printed, the substrate is placed on the base of the flip-chip welding machine, and the diced chip bump is placed on the carrier table, and the chip is picked up from the back by the vacuum suction head, and the bump is carried out by using the beam splitter. After alignment with the pads on the substrate, the suction head mounts the chip solder balls on the pads of the substrate. In addition to paying attention to the alignment of the solder ball and the pad when mounting the chip,...

AI Technical Summary

Problems solved by technology

The traditional flip-chip soldering process has high requirements on the coplanarity of the chip solder joints, the process is difficult to control, and the stability is poor. The conduction rate of the flip-chip soldered interconnect components obtained is not high, and there is poor contact between the solder joints and the substrate pads. And the problem of low soldering strength [1.Xiao G W, Chan P C H, Teng A, et al. Reliability Study and Failure Analysis of Fine Pitch Solder Bumped Flip Chip on Low-Cost Printed Circuit Board Substrate.Proc.of 51 st International Conference on Electronic Components and Technology, 2001: 598.2. Wolflick P. Feldman K. Lead-Free Low-Cost Flip-Chips ProcessChain: Layout Process, Reliability. International Electronics Manufacturing Technology (IEMT) Symposium, 2002: 27.]

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