Improving Stitch Bond on Hybrid Thick Film Substrate using Stand-Off Stitch Wire Bond Technique

2015 ◽  
Vol 2015 (1) ◽  
pp. 000425-000429 ◽  
Author(s):  
Richard C. Garcia
Keyword(s):  
Thick Film ◽  
Dielectric Materials ◽  
Glass Frit ◽  
Ceramic Substrate ◽  
Wire Bond ◽  
Design Requirements ◽  
The Wire ◽  
Film Substrate ◽  
Pull Tests ◽  
Associated Variables

Thick film technology is based on a paste containing glass frit that is screen printed and fused at high temperature onto various ceramic substrate materials. Softening or melting this glassy frit forms a cohesive layer, binding the conductors, resistors or dielectric materials to the ceramic. The dynamics of the printing process and inherent number of associated variables negatively impact the uniformity of the fired surface on a micro scale, which can lead to variation in the wire bonding process. Other processes associated with thick film substrate fabrication can cause problems as well. Laser trimming is used to adjust the value of printed resistors to meet design requirements. This ablation of printed resistors by high–powered pulse laser leaves a halo of debris and contamination on the ceramic substrate, which can cause wire bond lifting. In this paper, we will demonstrate a way to eliminate these problems using a bonding technique called Stand- Off Stitch bonding (SOS). This wire bond type is formed by first placing a ball bump at the second bond, or stitch, location on the thick film substrate, and then forming a normal wire that terminates on that bump. This places two ball bumps at each end of the wire, similar to a security bond. However, the ball bump is located under the stitch instead of on top. This SOS wire bond technique is compliant with the MIL-STD- 883 for a compound bond, where one bond is placed on top of another bond. With the gold bump placed on top of the gold thick film pad, the bump acts as a foundation for the stitch bond, providing a wider contact area and clean bond surface to secure a reliable stitch bond interconnect. With this change, an abrupt improvement to the resultant destruct wire pull tests can be achieved, promoting a robust, controlled process for wire bond interconnects.

Bonding behavior of Cu/CuO thick film on a low-firing ceramic substrate

1997 ◽  
Vol 12 (9) ◽  
pp. 2411-2418 ◽  
Author(s):  
Sang-Jin Lee ◽  
Waltraud M. Kriven ◽  
Jeong-Hyun Park ◽  
Young-Soo Yoon
Keyword(s):  
Thick Film ◽  
Adhesion Strength ◽  
Softening Point ◽  
Cupric Oxide ◽  
Glass Frit ◽  
Ceramic Substrate ◽  
Firing Process ◽  
Interfacial Region ◽  
Oxide Content ◽  
Barium Borosilicate Glass

The adhesion strength between a low-firing substrate consisting of an alumina/glass composite and a copper thick film was affected by the addition of cupric oxide and glass frit to the copper paste in a new co-firing process. An interlayer, 3–4 μm in thickness, was produced in the metal-ceramic interface during the new co-firing process due to the diffusion of copper. At the same time, the adhesion strength was improved by controlling the cupric oxide content. The addition of about 3 wt.% glass frit (softening point = 670 °C, based on the calcium-barium borosilicate glass composition) to the metal paste resulted in highest adhesion strength of 3 kg/mm2 with a shift of the debonding site toward the ceramic substrate within the interlayer. The shift of the debonding site could be observed by comparing the ratios of Al2O3/Cu and Ca concentration at the test pad areas on the substrate after debonding. The shift of the debonding site is attributed to the migration of glass frit into the interfacial region. The migration of glass frit occurred easily when the softening point of the glass frit was compatible with the new co-firing process, regardless of how much frit was used.

Reliability of Au-Ti for High Temperature Termination on Ferrite LTCC Inductors

2013 ◽  
Vol 2013 (HITEN) ◽  
pp. 000039-000045 ◽  
Author(s):  
James Galipeau ◽  
Matt Gerlach
Keyword(s):  
High Temperature ◽  
Thermal Shock ◽  
Thick Film ◽  
Thermal Ageing ◽  
Wire Bonding ◽  
Sputter Deposited ◽  
Commercial Applications ◽  
The Stability ◽  
Terminal Structure ◽  
Pull Tests

While ferrite Low Temperature Co-fired Ceramic (LTCC) inductor and transformer developments have undergone thermal shock and high temperature aging that focused on the stability of their electrical characteristics (resistance, inductance), little attention has been paid to their termination reliability at high temperatures. Testing has been done on AgPt and AgPd terminations with Ag5Cd95 and Pb88Sn10Ag2 solders for 2000 and 25 hrs, respectively. However, Ag5Cd95 is unusable in commercial applications due to ROHS restrictions while Pb88Sn10Ag2 is undesirable because of the high lead content. Sn96 solder and wire bonding are common attachment methods that have not been vetted. Initial investigations show that high Sn solders may interfere with bonding between the AgPt and AgPd termination materials and the ferrite bulk of the part. An alternative terminal structure for using Sn96 solder is created by electroplating Au and Ni; however, electroplating to ferrite is challenging due to the masking involved. Also, the preferred materials for wire bonding are thick film, thin film or electroplated Au. To this end an alternative termination structure using Au sputter deposited onto sputter deposited Ti is being investigated. This structure was chosen for its potential to be a lower cost alternative to thick film Au and for its potential for simpler manufacturing than electroplating. Tests involved measuring bond strength and resistance after thermal ageing and thermal shock. Baseline solder joint pull tests show strength comparable to other termination methods. Some issues with solder wetting of the terminals have been noted.

Mobile Packaging and Interconnect Trends

2014 ◽  
Vol 2014 (DPC) ◽  
pp. 1-21
Author(s):  
Brandon Prior
Keyword(s):  
Shear Strength ◽  
High Temperature ◽  
Thick Film ◽  
Cross Sections ◽  
Shear Test ◽  
Short Review ◽  
Test Machine ◽  
Die Attach ◽  
Shear Failures ◽  
Film Substrate

This paper will focus on emerging and fast growth package solutions to meet mobile products' density and cost requirements. A short review of where package miniaturization and modularization has taken us so far, and where it will lead in the next 5 years. Teardowns of high density systems and packages will be used to illustrate key points. Low temperature Ag sintering technology provides a lead-free die attachment compatible with high temperature (300°C) applications. Previous work with Ag sintering has required some pressure during the sintering process or been limited to small area die. In this paper, a pressureless sintering of micro-scale silver paste procedure is presented for large (8mm x 8mm) area die. Experimental combinations included: Ag metallized Si die, Au metallized Si die, Ag thick film substrate metallization, Au thick film substrate metallization, PdAg thick film metallization and sintering temperature. For Au metallization (die and/or substrate), the initial shear strength results were good with 8mm x 8mm die sintered at lower temperatures (200°C). The shear strength was out range of our shear test machine (100 kg), corresponding to >15.3 MPa. However, after aging for 24 hours at 300°C, the shear strength dropped significantly to 40.38 Kg (6.183 MPa). An SEM was used to characterize cross sections of as-built and aged sample. The decrease in die shear strength with high temperature sintering (250°C and 300°C) or high temperature aging is attributed to surface diffusion of Ag along the Au surface resulting in a dense Ag layer adjacent to the Au surface and a depletion layer within the die attach on the opposite side of the the dense Ag layer. Shear failures occurred through the depleted region. For Ag metallization, no decrease in shear strength was observed with 300°C aging. Shear strength of 8x8cm2 dies was out range of our shear test machine (>100 kg, >15.3 MPa) as-built. The shear strength remained out of range (>15.3MPa) after more than 2000 hours of 300C aging.

Evaluation of Glass Frits for Development of Lead-Free Thick Film Resistor

2010 ◽  
Vol 2010 (1) ◽  
pp. 000752-000759
Author(s):  
Xudong Chen ◽  
W. Kinzy Jones
Keyword(s):  
Electrical Properties ◽  
Temperature Coefficient ◽  
Thick Film ◽  
Glass Frit ◽  
Lead Free ◽  
Temperature Coefficient Of Resistance ◽  
Film Resistor ◽  
Thick Film Resistor ◽  
Glass Compositions ◽  
Free Glass

Glass frit is a major component of thick film resistor (TFR) for the production of hybrid circuits. More than thirty commercial lead-free glass frits with different compositions have been evaluated for developing a lead-free thick film resistor that is compatible with typical industry thick film processing and has comparable electrical properties as the lead bearing counterpart. Two glass compositions were selected out of 33 candidates for preparation of RuO2 based TFR inks, which were screen printed on alumina substrates and fired at 850°C. The preliminary results of these resistors showed that the sheet resistance spanned from 400 ohms per square (Ω/□) to 0.4 mega-ohms per square (MΩ/□) with 5–15% RuO2 and the hot temperature coefficient of resistance (HTCR) fell in a range of ±350ppm/°C.

Crystallization of Amorphous Thin BST/MgO(001) Films Grown by R.F. Magnetron Sputtering

1997 ◽  
Vol 493 ◽  
Author(s):  
D. Y. Noh ◽  
H. H. Lee ◽  
J. H. Je ◽  
H. K. Kim
Keyword(s):  
Thick Film ◽  
Intermediate Phase ◽  
Perovskite Phase ◽  
Pyrochlore Phase ◽  
Interface Area ◽  
Crystalline Orientation ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Experiment ◽  
Film Substrate

ABSTRACTThe crystallization of amorphous BST thin films was studied in a synchrotron x-ray scattering experiment. At around 600°C, an intermediate phase, which was suspected to be a metastable pyrochlore phase, was formed. The x-ray reflectivity curves showed that the film-substrate interface became rough as the pyrochlore-like phase was formed. This suggests that the pyrochlore phase was nucleated near the interface area. Upon further annealing to higher temperatures, the film transformed to the crystalline perovskite phase. The crystallization was sensitive to the film thickness. In the thin 550Å thick film, the crystallization occurred at 750 °C with the <001> preferred orientation. On the other hand, the 5500Å thick film became crystalline even at 500°C with random crystalline orientation. The observed thickness dependence of the crystallization suggests that the crystalline perovskite phase was nucleated in the bulk of the film, rather than the near interface area.

Assessment of 20 Micrometer Diameter Wires for Wire Bond Interconnect Technology

2007 ◽  
Author(s):  
S. Saiyed ◽  
S. A. Kudtarkar ◽  
R. Murcko ◽  
K. Srihari
Keyword(s):  
High Temperature ◽  
Stress Test ◽  
Small Diameter ◽  
Mechanical Tests ◽  
Stress Tests ◽  
Bonding Wire ◽  
Chip Area ◽  
Wire Bond ◽  
Ball Bonds ◽  
The Wire

In the domain of wire bonding technology, the size and pitch of bond pads and ball bonds are shrinking to accommodate the demand for higher I/Os and increased functionality per chip area. This trend serves as a catalyst for bonding wire manufacturers to continuously develop lower diameter bonding wires. One mil (25 μm) diameter bonding wire, used widely in this interconnection technique, is now being replaced by 0.8 mil (20 μm) diameter bonding wire. In keeping with the need for higher operating speeds and higher temperatures for today’s ICs, the reliability of ball bonds formed by small diameter wires is of concern and requires investigation. This study explores the effects of 0.8 mil (20 μm) diameter bonding wire on the wire bond ball joint reliability and compares these effects with 1.0 mil (25 μm) diameter bonding wire. The reliability of the ball bonds was assessed using mechanical tests (wire pull and ball shear) for units subjected to stress tests such as the unbiased highly accelerated stress test and high temperature storage tests. The results of this investigation reveal that both the wire diameters are able to sustain their integrity after moisture testing. But, the bond strength degrades after high temperature tests due to the Kirkendall voiding mechanism occurring between gold wire and the aluminum bond pad.

Optimization and Application of NTC Thick Film Segmented Thermistors

2013 ◽  
Vol 543 ◽  
pp. 491-494 ◽  
Author(s):  
Maria Vesna Nikolic ◽  
Obrad.S. Aleksic ◽  
Branka M. Radojcic ◽  
Miloljub D. Lukovic ◽  
Nenad Nikolic ◽  
...  
Keyword(s):  
Thick Film ◽  
Water Flow ◽  
Water Flow Rate ◽  
Input Voltage ◽  
Glass Frit ◽  
Water Current ◽  
Thermal Sensor ◽  
Layer By Layer ◽  
Reduced Dimensions ◽  
Water Mains

NTC thermistor paste for printing thermal sensors on alumina was formed of very fine Ni0.5Cu0.2Zn1.0Mn1.3O4 thermistor powder obtained by a combined mechanical activation/thermal treatment process, organic vehicle and glass frit. Sheet resistivity was measured using an R-test matrix and it was much lower than the value determined for pure nickel manganite thermistors. The thermistor exponential coefficient was calculated from the R[ diagram measured in the temperature range-30 to +120°C in a climatic chamber. Thick film segmented thermistors with reduced dimensions (optimized construction) were printed sequentially layer by layer, dried and fired at 850°C/10 min in air. Electrodes were printed of PdAg conductive and solderable paste. The samples obtained were characterized by electrical and thermal measurements. The obtained NTC segmented thermistors with reduced dimensions were applied in a thermal sensor for water flow in the water mains. It contained a cold thermistor for measuring input water temperature and a self-heating thermistor for measuring the dependence of water current on water flow rate at a set input voltage power. Initial measurements show that the thermal sensor system requires a low input voltage power making it much easier and safer for operation.

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