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In this study, solar ribbon solder joints were investigated to ensure the reliability of photovoltaic (PV) modules. Ribbon joints comprising two different solder compositions (wt. %: 60Sn40Pb, 62Sn36Pb2Ag) were used to perform thermal aging tests at three different temperatures (150 °C, 120 °C, and 90 °C) during a 1000-h period to analyze the resultant thermal degradation; shear tests were also performed to measure bond strengths. Initial bond strengths were 271.3 MPa and 241.3 MPa for 62Sn36Pb2Ag and 60Sn40Pb solder joints, respectively. Bonding strength decreased as a result of thermal aging, but was maintained at a value of around 130 MPa regardless of solder composition. Fracture surfaces from the shear test were observed to analyze for the constant bond strength phenomenon. It was verified that the shear fracture surface changed from the solder/sintered Ag interface and the sintered silver (Ag)/silicon (Si) wafer interface during thermal aging. Thus, the bond strengths and bonding characteristics of PV ribbon solder joints decreased under a thermal load, which could be attributed to a weakening of the bonding characteristics for sintered Ag silicon interfaces as opposed to a degradation of solder metallurgy.

In this study, the characteristics of growing an intermetallic compound(IMC) layer at solder joint in photovoltaic (PV) ribbon solder joint were investigated through the thermal ageing test. Also, the growth rate of IMC in the ribbon solder joint, which depend on the temperature and time, was predicted through the ageing test. That the ageing test were performed under three different conditions: 90 °C, 120 °C and 150 °C. Also, we prepare the two type solder composition(60Sn40Pb, 62Sn2Ag36Pb) to analyze Ag addition effect in solder to forming IMC layer. Following testing, the IMC layer formed Ag3Sn in Ag sintered layer by Sn diffusion phenomena at high temperature. The thickness of Ag3Sn in solder joint was measured by cross-section images during the thermal ageing test. The Ag3Sn IMC layer was filled in sintered Ag layer in 70 h under the harshest conditions of 150 °C and 750 h at 120 °C. The Ag3Sn thicknesses were calculated to activation energies forming IMC layer in solder joints. The results, the Ag3Sn growth rates under the various temperatures were predicted for long-term reliability of PV modules.

In this study, the degradation characteristics in MLCCs SAC305 lead-free solder joints were verified by thermal shock testing (from −40°C to 125°C). The thermal stress distribution in the solder joints was simulated utilizing ANSYS 13.0 and the thermal stress concentration was verified between the Ni plating layer and Cu electrode. After the test, the degradation of the mechanical characteristics was compared by conducting shear tests. The shear force decreased by 21.1% after 1200 cycles in C1608. In the case of C1005, the shear force decreased by 21.3% after 1000 cycles. The Ni3Sn4 IMCs were confirmed at the starting point at the shear fracture surface through ingredient analysis after the thermal shock test. Also, by observation of the cross-sections before and after the test, cracks were verified after thermal shock at the 1400th cycle. The cracks formed between the Ni plating layer and the solder joint. After the 1800th cycle, the Ni3Sn4 IMC thickness in C1608 grew to 8 μm. In C1005, the IMC thickness increased to 9 μm. Therefore, the Ni3Sn4 IMC growth affected the degradation and reliability reduction characteristics in the MLCC SAC305 lead-free solder joints. In the future, research aimed at preventing Ni3Sn4 IMCs should be carried out.

In this paper, Thermal Shock tests were performed varying the composition of the solder and ribbon thickness (A-type:0.2mm/60Sn40Pb, B-type:0.25mm/60Sn40Pb, C-type:0.2 /62Sn36Ag2Pb, D-type:0.25mm/ 62Sn36Ag2Pb) for evaluating the long-term reliability about Ribbon junction of Silicon solar cells. Thermal Shock test condition was performed during the 600cycles having -40 ~85 temperature range each 15 minutes; Ai Ai One cycle time was 30min. As a result, the initial efficiency of the A-type, B-type, and C, D-type were showed 15.0%, 15.4% and 15.8% respectively. After thermal shock test, the efficiency decreasing-rate of each type were as follow that A-type was 13.8%, B-Type was 15.4%. C-Type and D-Type was 15.3% and 16.2%, respectively. Also, degradation of surface changes and I-V characteristic curves were showed that the series resistance of the A, C-type was increased. Also, current lowering starting point of C-type shown 0.05volt(v) earlier than that of A-type. And B, D-type shown characteristics of composite lowering efficiency such as increase of series resistance, decrease of parallel resistance and cell damage. Therefore Initial solderability and efficiency of

Currently, only certification tests for photovoltaic modules are being made, so the exact cause of efficiency reductions due to aging are not fully analyzed. Before making a photovoltaic module in this study, we manufactured 3 line ribbon tabbed solar cells. After thermal shock and high-temperature and high-humidity testing, the changes in each solar cell component were analyzed and the cause of output reduction was identified. For the thermal shock testing, 500 cycles were performed for 15 min at each temperature, totaling 30 min per cycle, including ramp time to low temperature (−40°) and high temperature (85°). For the high-temperature and highhumidity tests, electrical characteristics were examined by exposing the cells to a temperature of 85° and relative humidity (RH) of 85% for 1000 h. After thermal shock and high-temperature and high-humidity testing, the relative efficiency reduction rates were 11.3% and 5.9%, respectively, and relative fill-factor-reduction rates were 6.0% and 0.7%, respectively. The causes of output power reduction were found to be grid finger disconnect due to damage of the internal cell and cell cracking after the thermal shock test. This meant that concentrated current was not collected and therefore lost. The light collection ability was also degraded by surface damage. Through this experiment, it was identified that the major cause of output power reduction after thermal shock and hightemperature and high-humidity testing was increased series resistance (RS) caused by external damage and not by deterioration of the cell itself.

Kang Min-Soo s³ Jeon Yu-Jae s³ Shin Young-EuiSchool of Mechanical Engineering, Chung-Ang University(Received 16 November 2013, Revised 18 December 2013, Accepted 18 December 2013)요 약본 논문에서는 태양전지의 두께 에 따라 가지 온도조건Ribbon (A-type:0.2mm, B-type:0.25mm) 3(-40~65 , -40~85 , -40~105 ) . , A, B type c’ c’ c’으로 열충격 시험을 수행하였다그 결과 별 초기 평균효율은 로 같았다하지만열충격 시험 후 에서 15.2% . , (600 Cycle) Condition 1 A-type 7.5%, B-type 7.7%, Condition 2 8.6%, 13.2% . Condition 3 11.6%, 19.에서는 를 나타내었다 에서는 각각 의 감소9%율을 나타내었다열충격 시험 후 보다 두께가 두꺼운 의 효율이 크게 감소하였다. A-type Ribbon B-type . 이는 모두 이종재료 접합부의 금속간화합물 층이 형성되어 전기적 저항이 증대된 것으A, B type (IMC)로 판단된다또한 의 특성 곡선 및 을 분석한 결과 층이 파괴되고병렬저항이 감소. , B-type I-V EL , p-n , 하여장기적 신뢰성에서 보다 더 취약한 것으로 나타났다향후 태양전지 형상에 따른 , A-type . Ribbon 장기 신뢰성 특성에 대해 수치해석 및 시뮬레이션 분석이 수반되어야 할 것이다 . 주요어

Kang Min-Soo s³ Jeon Yu-Jae s³ Shin Young-EuiSchool of Mechanical Engineering, Chung-Ang University(Received 16 November 2013, Revised 18 December 2013, Accepted 18 December 2013)요 약일본 연구에서는 열충격 시험을 통한 태양전지의 파괴모드에 따른 전기적 특성을 분석하였다시편은. Photovoltaic Module 3 line Ribbon Tabbing Solar Cell . 을 만들기 전 을 한 단결정 을 제작하였다열충격 시험 의 온도조건은 저온 고온 는 저온 고온 에서 Test 1 -40 , 85 , Test 2 -40 , 120 Ramping c’ c’ c’ c’Time 15 , 30 1 500 . 을 포함하여 각각 분씩총 분을 사이클로 사이클을 각각의 조건으로 수행하였다열충격 시험 후 에서는 의 효율 감소율과 의 감소율을 확인하였으며 에Test 1 4.0% 1.5% Fill Factor , Test 2서는 의 효율 감소율과 의 감소율을 확인하였다 촬영 24.5% 11.8% Fill Factor . EL(Electroluminescence)및 단면을 분석한 결과 과 시편 모두 표면 및 내부에서의 이 발견되었다, Test 1 Test 2 Cell Crack . 하지만 의 시험이 보다 가혹한 온도조건의 시험으로 인해 에서 나타나지 않았던, Test 2 Test 1 Test 1 , Cell Test 2 . , Test 1 Cell 파괴를 에서 확인하였다결국 에서 효율의 직접적인 감소 원인은 내부에서의 Crack , Test 2 Cell Crack Cell Cell 이며 에서는 내부에서의 및 파괴로 인한 자체의 성능저하로 효율이 크게 감소한다는 것을 본 실험을 통하여 규명하였다 . 주요어

In this study, The report analysed the characteristics of power drop in solar cell through thermal shock test. The solar cells were tested 500 cycles in lowest temperature and highest temperature by thermal shock test on ironbound conditions, that excerpted standard of PV Module(KS C IEC-61215). The result of the efficiency analysis through measure of I-V, efficiency of Cell decreased from 13.9% to 11.0% and decreasing rate was 20.9% after test. The result of the surface analysis through EL, solar cell has damage of gridfinger and ribbon joint. Cell cracks were founded in damage of cells through cross section of solar cells. Also, Fill factors were decreased from 72.3% to 62.0% after thermal shock test and decreasing rate is 11.8%. therefore, Yearly power drop is aggravated with facts that cell crack, damage of surface and power loss of cell by change of I-V characteristic curve with decreasing of parallel resistance.

In this study, The report analysed the characteristics of power drop and damage of surface in solar cell through high temperature and humidity test. The solar cells were tested during the 1000hr in temperature and 85% humidity conditions, that excerpted standard of PV Module(KS C IEC-61215). An analysis of the cell surface through EL(Electroluminescence), the cell has partly change of surface in yearly. Single-crystalline Solar cell efficiency is decreased from 17.7% to 15.6% and decreasing rate is 11.9%. On the other hand, Poly-crystalline Solar cell efficiency is decreased from 15.5% to 14.0% and decreasing rate is 9.3%. A comparison of the fill factor for analysis of electro characteristic in yearly, Single-crystalline Solar cell efficiency is decreased from 78.7% to 78.1% and decreasing rate is 4.7%. On the other hand, Poly-crystalline Solar cell efficiency is decreased from 78.1% to 76.7% and decreasing rate is 1.8%. Single-crystalline has more bigger power drop than poly-crystalline by the silicon purity and silicon atom arrangement. Also, FF decreasing rate has more bigger drop than efficiency decreasing rate for the reason that the damage of surface by exterior environmental factor is the more influence in cell than other reason that is decreasing FF by damage of p-n junction.

In this study, the characteristics and error ranges of the mechanical bonding strength were analyzed according to before and after thermal shock test for various chips of automotive application component using Sn-3.0Ag-0.5Cu solder. In the after thermal shock test, the mechanical bonding strengths tend to decrease, meanwhile decreasing rates of mechanical strengths were less then 12% at specimen`s bonding area below 3.5, and were from 17 to 21% at specimen`s bonding area above 12 . On the other hand, Specimen`s mean deviation rates were about 5% at specimen`s bonding area more than 12 . Inversely, at specimen`s bonding area is less then 3.5 , mean deviation rates were increased to about 8%. It means that the smaller device size is, the larger mean deviation rate. In addition, error ranges and deviation rates of the mechanical bonding strengths may differ slightly depending on their bonding area. Furthermore, process conditions as well as method of mechanical reliability evaluation should be established to reduce the error ranges of bonding strength.

This study investigated the characteristics of fracture behavior and mode on solder joints before and after thermal shock test for automotive application component using Sn-3.0Ag-0.5Cu solder, which has a outstanding property as lead-free solder. The shear strength was decreased with thermal cycle number, after 432 cycles of thermal shock test. In addition, fracture mode was verified to ductile, brittle fracture and base materials fracture such as different kind fractured mode using SEM and EDS. Before the thermal shock, the fractured mode was found to typical ductile fracture in solder layer. After thermal shock test, especially, Ag was found on fractured portion as roughest surface. Moreover, it occurred delamination between a PCB and a Cu land. Before thermal shock test, most of fractured mode in solder layer has dimples by ductile fracture. However, after thermal shock test, the fractured mode became a combination of ductile and brittle fracture, and it also could find that the fracture behavior varied including delamination between substrate and Cu land.

In this study, the characteristics of a photovoltaic (PV) ribbon (t = 0.25 mm) joint with 60Sn40Pb and 62Sn2Ag36Pb solders were evaluated using thermal shock tests. The thermal shock tests were performed under three conditions: −40–65 °C, −40–85 °C, and −40–105 °C. The results of these tests were analyzed using electroluminescence (EL) and cross-sectional images. Following testing, broken metal fingers (MFs) were confirmed near the solder joint. PV module degradation was attributed to the broken finger ratio (BFR) based on quantitative analysis of the dark rectangular (DR) regions on the EL images. In addition, the activation energy of the broken MFs was calculated from the increasing BFR. Thermal characteristic variations due to the added Ag in the PV ribbon solder joints were evaluated through observation of solder micro-structure changes following thermal shock tests.