표제지
국문초록
영문초록
목차
1. 서론 13
2. 이론적 배경 15
2.1. 솔더 접합부의 취성파괴(Brittle fracture) 15
2.2. PCB 표면처리 17
2.2.1. HASL(Hot Air Solder Leveling) 17
2.2.2. OSP(Organic Solderability Preservative) 17
2.2.3. ENIG(Electroless Ni / Immersion Au) & ENEPIG(Electroless Ni / Immersion Pd / Immersion Au) 18
2.2.2. Immersion Ag & Tin 19
2.3. 금속간화합물 (Intermetallic compound) 19
2.3.1. Sn / Ni system 19
2.3.2. Sn / Cu system 21
2.3.3. Sn-3.0Ag-0.5Cu based 솔더와 무전해 Ni/Au UBM 계면 반응 21
2.4. 솔더 접합부 파괴 (Fracture) 23
2.4.1. Black pad 23
2.4.2. 취성파괴에 영향을 주는 인자 25
3. 실험 방법 36
3.1. Test vehicle board 디자인 36
3.2. 솔더 접합부 충격특성 평가 방법 37
3.2.1. 고속전단시험 (High Speed Shear Test) 37
3.2.2. 낙하충격시험 (Board Level Drop Test) 37
3.2.3. 취성파괴율(Brittle Fracture%) 평가 지표 37
4. 결과 및 고찰 46
4.1. 전단강도 평가 46
4.2. 취성파괴 평가 48
4.2.1. 파괴모드 (Fracture Mode) 분석 48
4.2.2. 취성파괴율 (Brittle Fracture%) 분석 52
4.3. 낙하충격(Drop) 신뢰성 분석 54
4.4. Electroless Ni/Sn 취성파괴 메커니즘 56
4.4.1. 금속간 화합물 및 미세구조 56
4.4.2. NiSnP IMC 58
5. 결론 62
Reference 63
Table 2-1. Application of PCB surface finish. 28
Table 2-2. Interfacial reation layers formed between Sn-3.0Ag-0.5Cu solder, and OSP Cu, Ni-P base metals Formulations of epoxy adhesive samples. 32
Table 3-1. Schematic view of BGA package for a drop test. 42
Table 4-1. Comparison of vrittle fracture rate(rate data). 53
Fig.2-1. Phase diagram of Sn-Ni. 29
Fig.2-2. Phase diagram of Sn-Cu. 30
Fig.2-3. IMC formation process of ENIG/Sn. 31
Fig.2-4. Correlation of Fracture mode & shear strength. 33
Fig.2-5. Fracture mode of solder joint (ductile & brittle fracture). 34
Fig.2-6. Black pad. 35
Fig.3-1. Test vehicle board design. 39
Fig.3-2. Condition of reflow process. 40
Fig.3-3. Schematic of ball shear test. 41
Fig.3-4. Schematic view of a test vehicle for a drop test. 43
Fig.3-5. Schematic of drop tester. 44
Fig.3-6. Fracture mode determination by the percentage of the brittle fracture region on the fracture surface. 45
Fig.4-1. Comparison results of shear strength. 47
Fig.4-2. Fracture comparision on ductile & brittle area. 48
Fig.4-3. EDS results on ductile & brittle area. 49
Fig.4-4. Fracture mode variation with strain rate of HSS test. 51
Fig.4-5. Comparision of brittle fracture rate. 53
Fig.4-6. Drop reliability results 54
Fig.4-7. Cross-section SEM image of BGA package after drop test(x10k) 55
Fig.4-8. Cross section point of Ni-Sn-P layer. 56
Fig.4-9. Microstructure comparision in the solder 57
Fig.4-10. IMC thickness ans shape of solder joints 57
Fig.4-11. The TEM results of the (Cu, Ni) 6Sn5 IMC/Ni(P) interfaces. Thickness of P-rich Ni layer and size of nano-void formed in NiSnP layer vary with the type of surface finishing 59
Fig.4-12. The TEM micrographs of the (Cu,Ni)6Sn5 IMC/Ni-P interfaces(이미지참조) 60
Fig.4-13. EDX results 61