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Technical Briefs

Investigation on Laser Direct Welding of Quad Flat Pack Components

[+] Author and Article Information
Jimin Chen

e-mail: Jimin@bjut.edu.cn

Yi Qiu

Institute of Laser Engineering,
Beijing University of Technology,
Beijing 100124, China

1Corresponding author.

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received April 10, 2013; final manuscript received July 25, 2013; published online September 6, 2013. Assoc. Editor: Yi-Shao Lai.

J. Electron. Packag 135(4), 044501 (Sep 06, 2013) (9 pages) Paper No: EP-13-1024; doi: 10.1115/1.4025251 History: Received April 10, 2013; Revised July 25, 2013

The feasibility of laser direct welding quad flat pack (QFP) device without solder is analyzed and practiced. The relations between the tensile strength of QFP joints and laser welding parameters are investigated, and the optimized parameters are obtained. Further study of weld microstructure under the optimum parameters indicates the dependable metallurgical bonding has been formed. In accordance with the experimental parameters, the finite-element method is employed to simulate the temperature field of the welding process. The simulation results at optimum parameters of the welding spot's temperature distribution are discussed. The temperature rises linearly with the increment of loaded laser heating time, and the center temperature is rising much faster than other locations. The temperature is similar with actual measured highest temperature in this circumstance. It demonstrates the established model is satisfied, and the simulation result is reliable, which is significant to guide practical application.

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References

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Figures

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Fig. 1

The dynamic curve of pad Cu dissolving to SnPb solder by numerical calculation [10]

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Fig. 2

Schematic of the arrangement used for laser welding

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Fig. 3

The appearance of the QFP after laser direct welding

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Fig. 4

Relation between laser output power and tensile force of QFP microjoints

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Fig. 5

Relation between laser scanning speed and tensile force of QFP microjoints

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Fig. 6

Relation between laser repetition rate and tensile force of QFP microjoints

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Fig. 7

Fracture microstructures of QFP microjoints by laser direct welding (a) 14 W, 20 mm/s, 20 kHz and (b) 20 W, 12 mm/s, 20 kHz

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Fig. 8

Microstructures of the QFP joints welded by fiber laser without solder on Sn/Cu pad: (a) transverse section of the welding spot; (b) BSE of the welding bead; (c) EDS of marked a; and (d) EDS of marked b

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Fig. 9

The schematic diagram of the model

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Fig. 11

The temperature field distribution of different laser power welding

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Fig. 12

The temperature field distribution of different laser scanning speed

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Fig. 13

The temperature distribution at parameters of 20 W, 12 mm/s

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Fig. 14

The actual measurement maximum temperature at parameters of 20 W, 12 mm/s

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