Study on the Behavior Characteristics of Solder Balls for FCBGA Package

조승현,최진원,김한구 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.2

Warpage issues are of concern for flip chip Ball Grid Array (FCBGA) package reliability on thin substrates. Despite advantages in electrical performance of thin substrates, FCBGA warpage hampers reliability of the solder balls making up the ball grid array. Warpage and plastic strain of both the FCBGA package and solder balls are calculated under assembly conditions. Temperature dependent material properties were investigated using finite element analysis. FEM calculations of thermal deformation and equivalent plastic strain of solder balls considered to determine overall reliability of the solder balls. Solder ball plastic strain decreased with substrate core thickness. This can explain why solder ball reliability decreases with substrate thickness. Substrate surface warpage fluctuated significantly as core thickness decreased due to reduced stiffness. In addition, it is possible that solder balls and surface mounted components can be affected by surface fluctuations. Although thinner substrates have advantages in terms of electrical performance, high warpage is a critical root cause of package failure. Despite these tradeoffs, developing thinner substrates while avoiding warpage is a forefront issue. Warpage issues are of concern for flip chip Ball Grid Array (FCBGA) package reliability on thin substrates. Despite advantages in electrical performance of thin substrates, FCBGA warpage hampers reliability of the solder balls making up the ball grid array. Warpage and plastic strain of both the FCBGA package and solder balls are calculated under assembly conditions. Temperature dependent material properties were investigated using finite element analysis. FEM calculations of thermal deformation and equivalent plastic strain of solder balls considered to determine overall reliability of the solder balls. Solder ball plastic strain decreased with substrate core thickness. This can explain why solder ball reliability decreases with substrate thickness. Substrate surface warpage fluctuated significantly as core thickness decreased due to reduced stiffness. In addition, it is possible that solder balls and surface mounted components can be affected by surface fluctuations. Although thinner substrates have advantages in terms of electrical performance, high warpage is a critical root cause of package failure. Despite these tradeoffs, developing thinner substrates while avoiding warpage is a forefront issue.

Signal characteristic and test exploitation for intermittent nanometer-scale cracks

Lee, Hosung,Baeg, Sanghyeon Elsevier 2018 Microelectronics reliability Vol.84 No.-

<P><B>Abstract</B></P> <P>This paper analyzes signal distortion caused by nanometer-scale solder ball fractures. A solder ball fracture causes an intermittent open circuit on the transmission line. The resulting basic failure mechanism is a drop in signal voltage, due to the capacitance-induced Alternating Current (AC)-coupling effect (which is induced by the fractured solder ball). The two major contributing factors to this error are fracture height and the persisting duration of the consecutive same-logic-value signal. The required signal that induces a voltage drop, sufficient to detect nanometer-scale solder ball fractures, can be composed by repetition of certain signal patterns even for the I/O connections with run-length restrictions. The methodology is newly proposed to determine potential ranges of solder ball fractures. Test pattern generation is made by maximally exploiting the compounding effect of various sizes of same data bits to generate effective run-length that is larger than maximum run length for the purpose of detecting intermittent solder ball fractures. In DDR3 memory systems with 5-nm solder ball fractures, at least 29 bits of consecutive logic “1” or “0” signals are required to detect fractures. If the system has a maximum run-length of 10, 20, or 30 bits, the test signal—which has the equivalent voltage-dropping effect as 29-consecutive bits—can be generated with six, two, or one repetition of the test pattern, respectively; the test pattern is in the form of concatenated N-1 bits of consecutive logic “1” and 1 bit of logic “0” where N is the maximum run length. In addition, a SPICE simulation was conducted to confirm correlation between calculations and actual results. In the simulation, in order to detect a 5-nm solder ball fracture, at least 37 bits of consecutive signal were required.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The basic mechanism of the error by the nano-meter scale solder ball fracture </LI> <LI> The compounding effects of the switching signal for the fractured solder ball </LI> <LI> The methodology for selecting the target solder-ball-fracture range </LI> <LI> The methodology for generating the test pattern for the solder ball fracture </LI> </UL> </P>

Sn-3.0Ag-0.5Cu와 Sn-0.75Cu(-Ni,Bi) 솔더볼 합금조성에 따른 Heterogeneous BGA 솔더 접합부 열사이클 특성

배주영,김미송,현소희,이종현,문정탁,이영우,이슬기,김형태,백승관,홍원식 대한용접접합학회 2024 대한용접·접합학회지 Vol.42 No.2

Sn-3.0Ag-0.5Cu (SAC305) is one of the most commonly used Pb-free solder composition nowadays. A minor alloying element addition can improve mechanical properties and thermal reliability of the solder joint. Minor amount of Bithmuth (Bi) or Nickel (Ni) addition can improve mechanical properties of solder by solid solution strengthening, or ensure the structural stability of the intermetalllic compounds. Also, low melting temperature solder with Bithmuth can reduce the cost of soldering process and keep components from deterioration. In this study, reliability of heterogeneous and homogeneous solder joint in the ball-grid-array (BGA) package solder joint were investigated. Using Sn-3.0Ag-0.5Cu (SAC305) solder paste and two kinds of solder balls, we have investigated which combination of solder joint improves the thermo-mechanical reliability. SAC305 and SCN (Sn-0.75Cu-Ni,Bi) balls were used for homogeneous and hetrogeneous joints. Solder balls were attached in BGA package. To examine the solder joint reliability, thermal cycling test was conducted after reflow soldering. Shear strength measurement and cross-sectional analysis of the BGA package solder joints were carried out before and after 2000 cycles of the test. The shear strength of homogeneous solder joint decreased to 68.2% and heterogeneous decreased to 43.5%. The crosssectional analysis using scanning electorn microscopy (SEM) and electorn back-scattered diffraction (EBSD) showed the (Ni,Cu)6Sn5 and Cu6Sn5 IMCs which were generated in the solder joint, and the crack propagated longer in the homogeneous solder joint of SAC305 after the thermal cycling test. IPFM showed the grain refinement effect of the SCN solder joint after thermal cycling. The minor addition of Bi had played a role as dislocation pinning site and became to equiaxied grain, so that the lifetime of heterogeneous SCN solder joint was superior than that of the SAC305.

Bonding Property of Middle Temperature Sn-Ag-Cu Solder Ball Joint of Ball Grid Array Package

Joo Young Bae,Mi-Song Kim,Hye Min Lee,Seul Gi Lee,Young-Woo Lee,문정탁,Won Sik Hong 대한용접접합학회 2023 대한용접·접합학회지 Vol.41 No.5

Alloying effects of Nickel and Bismuth in SAC solder to achieve mechanical and microstructural evolution were investigated by comparing three different chemical composition of solders. Sn-3.0Ag-0.5Cu (SAC305) is the most commonly used for Pb-free solder and solder balls are based on Sn-Ag-Cu alloy composition. Compositions of solder balls were Sn-3.0Ag-0.5Cu (SAC305), Sn-1.2Ag-0.5Cu-0.05Ni (SAC1205N) and Sn-Ag-Cu-Ni-Bi based solder (SACNB). Organic solderability preservative (OSP) surface finished substrate, ball grid array (BGA) package arranged by 300 ㎛ diameter solder ball and Type 4 solder paste were used. Solder ball shear test of the BGA package was conducted before the reflow soldering. Board level package bonding process was carried out by hot air reflow soldering. Void content of the BGA solder joint was investigated after soldering. The microstructure evolution before and after thermal cycle test (TCT) was observed using scanning eletron microscopy (SEM) and energy dispersive spectroscopy (EDS). After TCT, intermetallic compound (IMC) refinement and solid solution strengthening effects of Bi element addition were observed in the solder matrix, and also any segregation of Bi element was not founded. Based on these result, it was found that the solder joint reliability of the middle and low temperature solder joints was improved.

Droplet-Based Manufacturing 공정에 의해 제조된 무연 솔더볼의 제조공정 변수 연구

엄호천,조경목,송인혁,한유동 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.1

Uniform droplet of lead-free solder balls was produced by using the Droplet-Based Manufacturing(DBM) process. Compositions of solder were Sn, Sn-3.6 wt.% Ag, and Sn-3.8 wt.%Ag-0.6 wt.% Zn. Effect of parameters such as orifice size, pressure difference, and frequency on the solder ball production was also investigated. Mean size, size distribution, and surface defect of solder balls were analyzed with variations of the parameters. Droplet spacing decreased with increasing frequency and decreasing pressure difference. Thus the size of solder ball decreased with increasing frequency and decreasing pressure difference. Size distribution fell within the narrow range of ±5% from the mean diameter of solder balls. The experimentally measured diameter of the solder balls fabricated by DBM process coincided quite well with the theoretically anticipated value of d_d=A d_o^2/3.

${\mu}BGA$ 패키지에서 솔더 볼의 초기 접합강도와 금 확산에 관한 연구

김경섭,이석,김헌희,윤준호,Kim, Kyung-Seob,Lee, Suk,Kim, Heon-Hee,Yoon, Jun-Ho 대한용접접합학회 2001 대한용접·접합학회지 Vol.19 No.3

This paper presents that the affecting factors to the solderability and initial reliability. It is the factor that the coefficient of thermal expansion between package and PCB(Printed Circuit Board), the quantity of solder paste and reflow condition, and Au thickness of the solder ball pad on polyimide tape. As the reflow soldering condition for 48 ${\mu}BGA$ is changed, it is estimated that the quantity of Au diffusion at eutectic Sn-Pb solder surface and initial bonding strength of eutectic Sn-Pb solder and lead free solder. It is the result that quantitative measurement of Au diffusion quantity is difficult, but the shear strength of eutectic Sn-Pb solder joint is 842 mN at first reflow and increases 879 mN at third reflow. The major failure mode in solder is judged solder fracture. So, Au diffusion quantity is more affected by reflow temperature than by the reflow times.

BGA용 Sn-3.5Ag 롤의 리플로 솔더링 특성

한현주,정재필,하범용,신영의,박재용,강춘식 대한용접접합학회 2001 대한용접·접합학회지 Vol.19 No.2

Reflow soldering characteristics of Sn-3.5Ag and Sn-37Pb balls for BGA(Ball grid Array) were investigated. Diameter of 0.76mm ball was set on a Cu/Ni/Au-coated pad and reflowed in air with changing peak soldering temperature and conveyor speed. Peak temperatures were changed from 240 to 28$0^{\circ}C$ for Sn-3.5Ag, and from 220 to 26$0^{\circ}C$ for Sn-37Pb balls. As results, heights of solder balls increased and widths decreased with peak soldering temperature. Through aging treatment at 10$0^{\circ}C$ for 1.000 hrs, average hardness of Sn-3.5Ag balls bonded at 25$0^{\circ}C$ cecreased from 14.90Hv to 12.83Hv And with same aging conditions, average shear strength of Sn-3.5Ag balls bonded at 26$0^{\circ}C$ decreased from 1727gf to 1650gf.

Electromigration Behavior of Cu Core Solder Joints Under High Current Density

Haksan Jeong,Choong‑Jae Lee,Jae‑Ha Kim,Jae‑yeol Son,Seung‑Boo Jung 대한금속·재료학회 2020 ELECTRONIC MATERIALS LETTERS Vol.16 No.6

Cu core solder ball (CCSB) is formed by a Cu core surrounded by solder alloy and is used as an interconnection material for 3D packaging. Herein, the electromigration behavior of CCSBs with an organic solderability preservative surface finish is compared with that of Sn–3.0Ag–0.5Cu (SAC) solder joint. The current density and temperature for electromigration test are 0.9 × 104 A/cm2 and 100 °C, which are in compliance with JEP154. The current density of the solder joint is analyzed using finite element method analysis and maximum current density of the SAC solder joint is 1.1 times higher than the CCSB solder joint. The CCSB solder joint is less affected by the current crowding effect because electrons move through the Cu core located at the center of the solder. A void form in the Cu electrode of the cathode that coincides with the simulated maximum current area of the solder joint. The electromigration reliability of the CCSB solder joint is superior to that of the SAC solder joint.

3-Dimensional Micro Solder Ball Inspection Using LED Reflection Image

Jee Hong Kim 한국인터넷방송통신학회 2019 Journal of Advanced Smart Convergence Vol.8 No.3

This paper presents an optical technique for the three-dimensional (3D) shape inspection of micro solder balls used in ball-grid array (BGA) packaging. The proposed technique uses an optical source composed of spatially arranged light-emitting diodes (LEDs) and the results are derived based on the specular reflection characteristics of the micro solder balls for BGA A vision system comprising a camera and LEDs is designed to capture the reflected images of multiple solder balls arranged arbitrarily on a tray and the locations of the LED point-light-source reflections in each ball are determined via image processing, for shape inspection. The proposed methodology aims to determine the presence of defects in 3D BGA shape using the statistical information of the relative positions of multiple BGA balls, which are included in the image. The presence of the BGA balls with large deviations in relative position imply the inconsistencies in their shape. Experiments were conducted to verify that the proposed method could be applied to inspection without sophisticated mechanism and productivity problem

Sn-3.5Ag, Sn-3.5Ag-0.7Cu, Sn-3.5Ag-3.0In-0.5Bi Solder를 이용한 $\mu$BGA Solder접합부의 열피로 수명예측

김연성,김형일,김종민,신영의 대한용접접합학회 2003 대한용접·접합학회지 Vol.21 No.3

This paper describes the numerical prediction of the thermal fatigue life of a $\mu$BGA(Micro Ball Grid Array) solder joint. Finite element analysis(FEA) was employed to simulate thermal cycling loading for solder joint reliability. Strain values, along with the result of mechanical fatigue tests for solder alloys were then used to predict the solder joint fatigue life using the Coffin-Manson equation. The results show that Sn-3.5mass%Ag solder had the longest thermal fatigue life in low cycle fatigue. Also a practical correlation for the prediction of the thermal fatigue life was suggested by using the dimensionless variable ${\gamma}$, which was possible to use several lead free solder alloys for prediction of thermal fatigue life. Furthermore, when the contact angle of the ball and chip has 50 degrees, solder joint has longest fatigue life.