Evaluation of Secondary Wire Bond Integrity on Ag Plated and Ni/Pd Based Lead Frame Plating Finishes

2009 ◽  
Author(s):  
G. Srinivasan ◽  
R. Murcko ◽  
K. Srihari
Keyword(s):  
High Temperature ◽  
Failure Analysis ◽  
Wire Bonding ◽  
Strength Test ◽  
Lead Frame ◽  
Wire Bond ◽  
Pull Strength ◽  
High Temperature Storage ◽  
The Wire ◽  
Temperature Storage

As the legislatures demand the use of lead (Pb) free plating finishes in lead frame manufacturing, different plating finishes are being offered by the lead frame makers. Lead frames are most often designed with two different Pb free plating finishes, primarily tin and nickel/palladium (Ni/Pd) based. The tin post mold plated lead frames use silver selective plating on the lead fingers for secondary wire bonding whereas the pre-plated Ni/Pd based lead frames use the same Ni/Pd based finish throughout. Enhanced versions of Ni/Pd based plating finishes such as nickel/palladium/gold (Ni/Pd/Au), nickel/palladium/gold-palladium (Ni/Pd/Au-Pd) and nickel/palladium/gold-silver (Ni/Pd/Au – Ag) are now available to further improve the wirebondability, solderability and reliability of the package. The development of a new lead frame finish involves a wide variety of concerns which must be addressed and thus mandates further evaluation of these new structures. Using the common Pb free lead frame plating finish of selectively plated silver (Ag) as the basis, a comparative approach was used to evaluate the secondary wire bond integrity of a 25 micron (1 mil) thick gold wire on Ni/Pd based lead frame plating finishes. The integrity of the secondary wire bonds for different plating finishes was investigated at various assembly thermal exposure stages using the wire pull strength test as the arbiter. Reliability tests, such as High Temperature Storage (HTS) and Unbiased Highly Accelerated Stress Test (UBHAST), were also conducted. Finally, failure analysis was conducted with the help of metallographic cross sectioning, SEM/EDX (Scanning Electron Microscope/Energy Dispersive X-ray) analysis and statistical analysis of the wire pull strength test results. Before wire bonding the lead frames, the plating surface was investigated for its surface integrity with the help of plating quality tests, such as: (i) adhesive tape test, (ii) bend test, (iii) heating test and the (iv) scribing test. Also, since wire pull is a destructive test, a statistical method called a nested gauge R&R study was used to estimate the repeatability and reproducibility of the measurement system. Failure analysis showed that there were silver and copper migrations over the Ag plated lead frame when exposed to a high temperature storage test at 175°C for 1000 hrs, but this did not affect the bond integrity. However, the Ni/Pd based lead frames did not show any metal migration since nickel acts as a barrier against the base metal diffusion.

High temperature storage reliability investigation of the Al–Cu wire bond interface

2012 ◽  
Vol 52 (9-10) ◽  
pp. 1966-1970 ◽  
Author(s):  
R. Pelzer ◽  
M. Nelhiebel ◽  
R. Zink ◽  
S. Wöhlert ◽  
A. Lassnig ◽  
...  
Keyword(s):  
High Temperature ◽  
Wire Bond ◽  
High Temperature Storage ◽  
Bond Interface ◽  
Temperature Storage

Nanoindentation Study on Heat Treated Gold Wire Bonding

2016 ◽  
Vol 857 ◽  
pp. 31-35
Author(s):  
Wan Yusmawati Wan Yusoff ◽  
Azman Jalar ◽  
Norinsan Kamil Othman ◽  
Irman Abdul Rahman
Keyword(s):  
High Temperature ◽  
Storage Period ◽  
Gold Wire ◽  
Constant Load ◽  
Wire Bonding ◽  
Nanoindentation Test ◽  
High Temperature Storage ◽  
Gold Ball ◽  
Ball Bonds ◽  
Temperature Storage

The effect of high temperature storage of gold ball bonds towards micromechanical properties has been investigated. Gold wire from thermosonic wire bonding exposed to high temperature storage at 150 °C for 10, 100 and 1000 hours. The nanoindentation test was used in order to evaluate the high temperature storage effect on wire bonding in more details and localized. Prior to nanoindentation test, the specimens were cross-sectioned diagonally. The constant load nanoindentation was performed at the center of gold ball bond to investigate the hardness and reduced modulus. The load-depth curve of nanoindentation for the high temperature storage gold wire has apparent the discontinuity during loading compared to as-received gold wire. The hardness value increased after subjected to high temperature storage. However, the hardness decreased when the storage period is extended. The decreasing in the hardness value may due to the grain size of Au metal which recrystallized after subjected to high temperature storage. The results obtained from nanoindentation is important in assessing the high temperature storage of wire bonding.

High-Temperature Reliability of Wire Bonds on Thick Film

2017 ◽  
Vol 2017 (1) ◽  
pp. 000531-000535 ◽  
Author(s):  
Zhenzhen Shen ◽  
Aleksey Reiderman
Keyword(s):  
Thin Film ◽  
High Temperature ◽  
Thick Film ◽  
Thick Films ◽  
Wire Bonding ◽  
Substrate Side ◽  
Pull Strength ◽  
Wire Bonds ◽  
The Wire ◽  
Gold Wires

Abstract In a harsh environment, wire-bonded interconnects are critical for overall reliability of microelectronic assemblies. Aluminum is the dominating metallization of the die wire bonding pads and aluminum wires are used to achieve monometallic bonding system on die side. On the substrate side, a monometallic connection is not readily available and typically involves expensive aluminum thin-film deposition or labor-intensive bonding tabs. Nickel-palladium-gold galvanic or electro-less plating stacks are also used to improve bondability and reliability of non-monometallic Al wire bonds on the substrate side. However, these plating stacks do not perform well after excursions above 330°C that are needed for the attachment of die and passives prior to wire bonding. At these temperatures, both palladium and nickel diffuse through the gold and form surface oxides that degrade wire bondability. In monometallic wire-bonding schemes, in addition to aluminum wires gold wires within same assembly are often also needed, for example, when some die is only available with gold-plated bond pads, or to connect substrates to gold-plated pins of hybrid housings. A universal substrate metallization, compatible with aluminum wire and gold wire, is therefore desirable. Thin-film substrates produced by sequential deposition and etching of gold metal, barrier metals, then aluminum metal is a good working solution, but it can be as much as ten times more expensive than other types of substrates. Printed thick-film metallization, a well-established technology, have been widely used for hybrid substrates. Silver-based thick films are inexpensive and capable of accepting aluminum and gold bonds. However, the silver-aluminum bonds are seldom used because of intermetallic formation and subsequent degradation triggered by multiple factors like temperature, humidity, and the presence of halogens. Pd and Pt are often added to the Ag thick films to decrease this effect, but potential usability and the reliability of these formulations in extreme temperature environments is not well researched. For this study, samples of Pt/Ag thick-film metallization were printed on Al2O3 substrates, and 25-um and 250-um aluminum wires and 50-um gold wires were wedge bonded in daisy chain to the substrate. The test vehicles were subjected to high-temperature testing at 260°C and 280°C. Thermal cycling tests from −20°C to 280°C were also performed. Mechanical and electrical characterizations of the wire bonds were conducted periodically. These tests included resistance and pull-strength measurements. Failure analysis of the bond joints was performed to understand the results of the tests. The 250-um Al wire and 25-um Al wire showed no significant changes until a critical time-at-temperature was reached. After reaching this temperature, the wire/substrate interface resistance rapidly increased to values as high as 40 Ohms for the 25-um Al wires. However, the pull strength remained within standard throughout the tests of up to 1200 hours. The relationship between time to failure and the temperature is presented in the paper. There was a four times life increase of bonds with every 20°C. With gold wires, no dramatic increase of bond resistance was observed, only a slight increase with time. The pull strength of Au wires remained stable throughout the time at high temperature. The tested Ag/Pt thick film metallization was found to be compatible with bonding of the gold wires and the aluminum wires for high-temperature applications up to an Arrhenius equivalent of 800 hours at 260°C. Additionally, Parylene HT coating was vapor-deposited on one set of 250-um Al wire-bonding samples. This set of samples demonstrated doubling of its useful life as compared to the uncoated samples.

NSOP Reduction for QFN RF-IC Packages

2016 ◽  
Vol 2016 (1) ◽  
pp. 000530-000534
Author(s):  
Mumtaz Y. Bora
Keyword(s):  
Form Factor ◽  
Failure Modes ◽  
Cost Effective ◽  
Wire Bonding ◽  
Lead Frame ◽  
Front End ◽  
Wire Bond ◽  
The Wire ◽  
Copper Lead ◽  
Rf Ic

Abstract Wire bonded packages using conventional copper lead frame have been used in industry for quite some time. The growth of portable and wireless products is driving the miniaturization of packages resulting in the development of many types of thin form factor packages and cost effective assembly processes. Proper optimization of wire bond parameters and machine settings are essential for good yields. Wire bond process can generate a variety of defects such as lifted bond, cracked metallization, poor intermetallic etc. NSOP – Non- stick on Pad is a defect in wire bonding which can affect front end assembly yields. In this condition, the imprint of the bond is left on the bond pad without the wire being attached. NSOP failures are costly as the entire device is rejected if there is one such failure on any bond pad. The paper presents some of the failure modes observed and the efforts to address NSOP reduction [1].

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