On the failure mechanism in lead-free flip-chip interconnects comprising ENIG finish during electromigration

Gorywoda, Marek; Dohle, Rainer; Wirth, Andreas; Burger, Bernd; Goßler, Jörg

doi:10.1109/ectc.2015.7159881

Cited by 6 publications

(6 citation statements)

References 9 publications

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“…Such catastrophic consumption of the Ni-P metallization is observed when Ni-P was deposited on a Cu layer. Cu seems to promote the dissolution of Ni-P layers and their catastrophic thinning [8,9]. In our study, we have observed a development of a very narrow separation (gap or crack) at the interface between UBM and solder or inside the UBM, respectively (see Fig.…”

Section: Discussionsupporting

confidence: 54%

“…Ceramic substrates possess higher heat conductivity than PCBs; consequently they dissipate heat more effectively. The temperature increase measured on chips assembled on PCBs amounted to 20 °C for the current of 141 mA (60 µm bumps) and to 28 °C for the current of 157 °C (50 µm bumps) [9]. From Fig.…”

Section: Discussionmentioning

confidence: 91%

“…For the sake of comparison, the result of our previous study on electromigration in lead-free bumps on conventional PCBs can be taken into account. The study used the same chip design; the diameter of the bumps was however equal to 60 µm or 50 µm [9]. Among other conditions, EM tests there were conducted at a temperature of 125 °C with applied currents of 141 mA (current density of 5 kA/cm²) for 60 µm bumps or 157 mA (current density of 8 kA/cm²) for 50 µm bumps, respectively [9].…”

Section: Discussionmentioning

confidence: 99%

“…The study used the same chip design; the diameter of the bumps was however equal to 60 µm or 50 µm [9]. Among other conditions, EM tests there were conducted at a temperature of 125 °C with applied currents of 141 mA (current density of 5 kA/cm²) for 60 µm bumps or 157 mA (current density of 8 kA/cm²) for 50 µm bumps, respectively [9]. The MTTF for these conditions were experimentally determined to amount to 1,120 h for chips with 60 µm solder joints or 2,416 h for chips with 50 µm bumps, respectively.…”

Section: Discussionmentioning

confidence: 99%

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Study on electromigration in flip chip lead-free solder connections with 40 μm or 30 μm diameter on thin film ceramic substrates

Gorywoda

Dohle

Kandler

et al. 2015

International Symposium on Microelectronics

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Electromigration comprises one of the processes affecting the long-term reliability of electronic devices; it has therefore been the focus of many investigations in recent years. In regards to flip chip packaging technology, the majority of published data is concerned with electromigration in solder connections to metallized organic substrates. Hardly any information is available in the literature on electromigration in lead-free solder connections on thin film ceramic substrates. This work presents results of a study of electromigration in lead-free (SAC305) flip chip solder bumps with a nominal diameter of 40 μm or 30 μm with a pitch of 100 μm on silicon chips assembled onto thin film Al2O3 ceramic substrates. The under bump metallization (UBM) comprised of a 5 μm thick electroless nickel immersion gold (ENIG) layer directly deposited on the AlCu0.5 trace. The ceramic substrates were metallized using a thin film multilayer (NiCr-Au(1.5 μm)-Ni(2 μm) structure on the top of which wettable areas were produced with high precision by depositing flash Au (60 nm) of the required diameter (40 μm or 30 μm). All electromigration tests were performed at the temperature of 125 °C. Initially, one chip assembly with 40 μm and one with 30 μm solder bumps was loaded with the current density of 8 kA/cm2 for 1,000 h. The assemblies did not fail and an investigation with SEM revealed no significant changes to the microstructure of the bumps. Thereafter seven chip assemblies with 40 μm solder bumps and five assemblies with 30 μm bumps were subjected to electromigration tests of 14 kA/cm2 or 25 kA/cm2, respectively. Six of the 40 μm-assemblies failed after 7,000 h and none of the 30 μm-assemblies failed after 2,500 h of test duration so far. Investigation of failed samples performed with SEM and EDX showed asymmetric changes of microstructure in respect to current flow. Several intermetallic phases were found to form in the solder. The predominant damage of the interconnects was found to occur at the cathode contact to chip; the Ni-P layers there showed typical columnar Kirkendall voids caused by migration of Ni from the layers into the solder. Failure of the contacts apparently occurred at the interface between Ni-P and solder. In summary, the results of the study indicate a very high stability of lead-free solder connections on ceramic substrates against electromigration. This high stability is primarily due to a better heat dissipation and thus to a relatively low temperature increase of the ceramic packages caused by resistive heating during flow of electric current. In addition, the type of the metallization used in the study seems to be more resistant to electromigration than the standard PCB metallization as it does not contain a copper layer.

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Section: Discussionsupporting

confidence: 54%

Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Study on electromigration in flip chip lead-free solder connections with 40 μm or 30 μm diameter on thin film ceramic substrates

Gorywoda

Dohle

Kandler

et al. 2015

International Symposium on Microelectronics

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“…Manakala, jelas kelihatan dua lapisan terbentuk pada antaramuka substrat-pateri bagi PCB/Ni iaitu lapisan IMC dan lapisan Ni (Rajah 1(c)). Lapisan IMC yang terbentuk ialah (Cu, Ni) 3 Sn 4 tumbuh kesan daripada salutan Ni (Gorywoda et al 2015;Yoon & Jung 2016…”

Section: Bahan Dan Kaedahunclassified

Pengawalan Pertumbuhan Sebatian antara Logam Sambungan Pateri-Papan Litar Bercetak Menggunakan Salutan Nikel

Bakar

Jalar²,

Abdullah

et al. 2018

JSM

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ABSTRAKBahan aloi pateri dalam kumpulan Sn-Ag-Cu (SAC) merupakan bahan pematerian yang bebas plumbum digunakan secara meluas dalam industri elektronik. Antarasambungan pateri bertindak untuk menghubungkan komponen elektronik pada papan litar bercetak (PCB). PCB memainkan peranan yang penting dalam tindak balas pematerian dan mikrostruktur antarasambungan pateri-substrat seterusnya mempengaruhi kebolehharapan suatu sambungan pateri. Pes pateri Sn0.3Ag0.7Cu (SAC0307) dipaterikan pada tiga jenis PCB iaitu PCB tanpa salutan (PCB/Cu) sebagai sampel kawalan, PCB dengan salutan timah (PCB/Sn) dan PCB dengan salutan nikel (PCB/Ni). Kajian ini bertujuan untuk mengkaji kesan salutan permukaan PCB ke atas pertumbuhan sebatian antara logam (IMC) selepas uji kaji penuaan sesuhu yang berbeza selama 1000 jam. Keputusan menunjukkan purata ketebalan lapisan IMC ~ 5.7 μm serta kadar pertumbuhan lapisan IMC yang paling rendah adalah selari dengan tenaga pengaktifan tertinggi dengan salutan Ni iaitu 41 kJ/mol berbanding PCB/Cu dan PCB/Sn. Ini bermakna salutan Ni pada PCB mampu mengawal pertumbuhan IMC sehingga lebih kurang 40% berbanding salutan Sn dan tanpa salutan.Kata kunci: Antarasambungan pateri; salutan Ni; sebatian antara logam; Sn-Ag-Cu; tenaga pengaktifan ABSTRACT Solder alloy materials in Sn-Ag-Cu (SAC) group is a lead free soldering materials which widely used in the electronics industry. Solder interconnection act to attach electronic components to printed circuit boards (PCBs). PCB plays an important role in soldering reactions and microstructure solder interconnection-substrate which further affects the reliability of a solder joint. Solder paste of Sn0.3Ag0.7Cu (SAC0307) is soldered on three types of PCB ie PCB without coating (PCB/Cu) as controlled sample, PCB with tin coating (PCB/Sn) and PCB with nickel coating (PCB/Ni). The purpose of this study was to investigate the effect of PCB surface coating on the growth of intermetallic compound (IMC) after different aging tests for 1000 h. The results showed that the average IMC layer thickness ~ 5.7 μm together with lowest IMC layer growth rate is in line with highest activation energy, 41 kJ/mol with the usage of Ni coating as compared to PCB/Cu and PCB/Sn. This means that the Ni coating on PCB is able to control IMC growth up to 40% compared to Sn coating and non-coating.

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Advancement of Printed Circuit Board (PCB) Surface Finishes in Controlling the Intermetallic Compound (IMC) Growth in Solder Joints

Atiqah

Jalar

Bakar

et al. 2022

Topics in Mining, Metallurgy and Materials Engineering

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On the failure mechanism in lead-free flip-chip interconnects comprising ENIG finish during electromigration

Cited by 6 publications

References 9 publications

Study on electromigration in flip chip lead-free solder connections with 40 μm or 30 μm diameter on thin film ceramic substrates

Study on electromigration in flip chip lead-free solder connections with 40 μm or 30 μm diameter on thin film ceramic substrates

Pengawalan Pertumbuhan Sebatian antara Logam Sambungan Pateri-Papan Litar Bercetak Menggunakan Salutan Nikel

Advancement of Printed Circuit Board (PCB) Surface Finishes in Controlling the Intermetallic Compound (IMC) Growth in Solder Joints

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