Improvement of drop reliability in OSP/Cu pad finished packages

Kim, Pyoung-Wan; Kim, Bo-Seong; Ahn, Eun-Chul; Chung, Taeyoung

doi:10.1109/eptc.2006.342710

Cited by 5 publications

(5 citation statements)

References 6 publications

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“…CuOSP Finish: For Cu OSP pad finish on the package, it has been shown that SAC125Ni solder alloy performs better in drop test compared to SAC305 and SAC405 solder alloys [1,3]. This is again shown in Figure 4a and 4b.…”

Section: Solder Alloymentioning

confidence: 77%

“…On the other hand, the solder bump only contributed about 50% of the final joint volume in the case of LGA, resulting in final joint composition of close to Sn2.0Ag0.5Cu. As it has been shown previously that high Ag in the joint results in lower drop performance [1,2,3], the lower performance of LGA here is primarily due to this factor. This can also been seen clearly by combining results of Figure 12a, 7.5x7.5mm die, with those from Figure 5 where solder paste was also SAC105.…”

Section: Solder Joint Sizementioning

confidence: 78%

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Impact of package design and materials on reliability for temperature cycling, bend, and drop loading conditions

Syed

Scanlan

Cha

et al. 2008

2008 58th Electronic Components and Technology Conference

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This paper presents a collection of test data showing how the choice of package design and material can have a different effect on performance depending on the loading conditions. Board level temperature cycling, drop (JESD22-B111), and cyclic bend (JESD22-B113) tests were performed on 0.4mm ball pitch packages. Factors investigated for this evaluation include mold compound material, mold cap thickness (0.45 vs. 0.7mm), ball pad finish (NiAu vs. Cu OSP), solder ball composition (SAC305, SAC105, SAC125Ni, Sn3.5Ag), solder volume (ball vs. bump), package material (RoHS vs Green), and board material (RoHS vs Green). The data presented in this paper indicates that lower silver content solder balls perform better under drop conditions, while temperature cycling reliability suffers as silver content decreases.In addition, mold compound material and thickness, die size, and solder volume have the opposite effect depending on the loading condition. The Green material for test board also showed lower performance than RoHS compliant board material. IntroductionThe reliability of an electronic package is ultimately determined by the environment and application in which it is used. Traditionally, only temperature and power cycling were of concern for board level reliability, and CTE mismatch between the package and the board was considered as the primary failure mechanism. However, due to the proliferation of electronic devices across market segments ranging from automotive to small, hand-held devices, electronic packages experience mechanical loading conditions other than just temperature cycling. Handheld products are prone to being dropped and their keys are pressed millions of times during the useful life to send text messages. Similarly electronic assemblies for telecom and automotive applications experience mechanical bending and shock conditions during installation and actual use conditions. This mechanical drop and cyclic bending due to key press have introduced failure modes where flexibility of the package is more important than the CTE mismatch. These additional failure mechanisms have their implications on package design and material selection. The one-size-fits-all model is no longer suitable for package design and material selection and customization is necessary

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Section: Solder Alloymentioning

confidence: 77%

Section: Solder Joint Sizementioning

confidence: 78%

Impact of package design and materials on reliability for temperature cycling, bend, and drop loading conditions

Syed

Scanlan

Cha

et al. 2008

2008 58th Electronic Components and Technology Conference

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“…There are many publications reporting that SnAgCu solder joints with low Ag content performed better in drop test of μBGA [3][4][5][6][7][8][9][10][11][12]. In contrast, the performance of SnAgCu solder joints in thermal cycling improved as the Ag content increases [10,[13][14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 93%

Thermal cycling reliability of SnAgCu solder joints in WLCSP

Zeng

Nangia

2014

2014 IEEE 16th Electronics Packaging Technology Conference (EPTC)

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It has been widely reported in the literature that for packages that are required to pass thermal cycling test, the SnAgCu solder joints should have high Ag content. In this study, thermal cycling performance of a wafer level chip-scale package was evaluated with different combinations of high Ag solder (Sn3.9Ag0.6Cu) and low Ag solder (Sn1.2Ag0.5Cu) with thick and thin PCB. It was found that with the low Ag solder ball the package mounted on a thin PCB had better performance. Metallurgical analysis of solder joints, mechanical modeling of the package mounted on boards, and coplanarity measurement of the printed circuit boards were performed to understand the results. Because of the CTE mismatch between PCB and die, PCB warpage resulted in high tensile stress in solder joints in the central area, causing cracking of re-distribution layer Cu. The softer solder alloy Sn1.2Ag0.5Cu helped reduce the stress, leading to better performance in thermal cycling test. IntroductionWafer level chip-scale package (WLCSP) brings benefit to the miniaturization of devices and low cost. Compared to μBGA, the printed circuitry board (PCB) assembly with WLCSP has simpler structure and but greater stress in solder joints. See Fig. 1. In μBGA, Si die is glued on a polymer substrate and wire bonded to the pads on the substrate. Solder balls are between two polymer materials. Since the die is attached on polymer substrate by adhesive, the stress due to mismatch of coefficien of thermal expansion (CTE) between die and polymer substrate can be largely released by the glue and wires. However, for WLCSP, solder balls are placed on die. It is flip chip assembled directly on the PCB. The CTE mismatch between Si die and PCB is much larger than between substrate and PCB in the case of μBGA. The solder balls between die and PCB are under higher stress than the ones between μBGA substrate and PCB. The CTE of RF-4 PCB is about 16 ppm/°C [1], but it is only 2.5 ppm/°C for die [2]. Because of this, underfill encapsulate is recommended for WLCSP to get better package reliability. However, because of

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“…The presence of voids are one of the major detects in solder that may be unavoidable in the lead-free electronic assembly industry [10]. Kirkendall holes were one of the reasons that descended the solder joints, because when it was forced, stress concentration prior to emergement near the holes, consequently evolved into cracks [12][13]. HASL and OSP finishes had the best crack resistant because holes have never been found from the beginning to the end.…”

Section: Growth Kinetics On Multiple Reflowsmentioning

confidence: 99%

“…However, many shortages have limited the use of it, such as the weak of high temperature shock resistant and the brittle of the intermatellic compounds (IMCs). OSP pad treatment has high strength solder joints and is environment friendly, so it is widely used in electronic assembly industry [2][3]. The ENIG finish is less expensive than electrolytic Ni/Au but the former may cause"black-pad" phenomenon [4][5], so resulting in soldering joint reliability decreasing.…”

Section: Introductionmentioning

confidence: 99%

Influence of multiple reflows and thermal shock on interfacial IMC of solder joints between Sn0.3Ag0.7Cu solder/pads(HASL, OSP, electrolytic Ni/Au and ENIG PCB finishes)

Wei

Luo

Shi

et al. 2011

2011 International Symposium on Advanced Packaging Materials (APM)

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The effects of multiple reflows and thermal shock on interfacial reaction of the solder joints between Sn-0.3Ag-0.7Cu solder/pads (HASL, OSP, electrolytic Ni/Au and ENIG PCB finishes) were systematically investigated in this work. The results showed that the scallop Cu 6 Sn 5 phase were formed in HASL and OSP finish pads during reflows, whereas the cylinder-type (Cu,Ni) 6 Sn 5 near the solder and needle-type (Ni,Cu) 3 Sn 4 adjacent to the Ni layer were formed in electrolytic Ni/Au and ENIG finish pads. For all the four kinds of finishes, the thickness of IMCs increased with reflow times increasing, and the interfacial IMCs growth was controlled by grain boundary diffusion; the growth rate at Cu surface was faster than at Ni surface. Furthermore, it was also indicated that the interfacial IMCs growth were not notable with thermal shock cycle numbers increasing, but Kirkendall voids could be observed in the Sn-Cu-Ni intermetallic compounds layer for electrolytic Ni/Au and ENIG Finish Under thermal shock tests.

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Improvement of drop reliability in OSP/Cu pad finished packages

Cited by 5 publications

References 6 publications

Impact of package design and materials on reliability for temperature cycling, bend, and drop loading conditions

Impact of package design and materials on reliability for temperature cycling, bend, and drop loading conditions

Thermal cycling reliability of SnAgCu solder joints in WLCSP

Influence of multiple reflows and thermal shock on interfacial IMC of solder joints between Sn0.3Ag0.7Cu solder/pads(HASL, OSP, electrolytic Ni/Au and ENIG PCB finishes)

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