tips for creating consistency in solderingsome tips on the market are unnecessarily stylized; for...

BRAZING & SOLDERING TODAY

MARCH 201160

Poor hand soldering results are costingelectronic manufacturers thousands ofdollars every year. There’s no secret to pro-ducing a good solder joint; the challengecomes with repeating this feat for all jointsin the assembly at production speeds.

The characteristics of a good solderjoint are well understood, and establishedsoldering standards such as IPC J-STD-001, Requirements for Soldered Electricaland Electronic Assemblies, provide an ac-curate guide to achieving satisfactory re-sults. However, production departmentsfrequently experience yield and through-put deficiencies equating to more than thecost of employing an additional operator.Finding a solution can make an apprecia-ble difference to business performance.

Understanding four factors will helpestablish a robust and consistently repeat-able soldering process, resulting in lowerdefect rates and ownership costs. Theseinclude optimizing the flow of energy fromthe soldering iron to the joint, and thenunderstanding how performing multiplesoldering operations in rapid successioncan alter this flow. With this knowledge,the relevant equipment performance pa-rameters can be assessed.

The Tip-Heater Interplay

Figure 1 describes how energy is trans-ferred into the connection, from the sol-dering iron, to raise the joint to a suitablesoldering temperature. The IPC J-STD-001 soldering standard, as well as manyproprietary standards based on its recom-mendations, specify this as 40°C above thesolder alloy’s melting point. The best prac-tice, then, is to keep the iron on the jointfor between 2 and 5 s. This is the acceptedmethodology to produce a solder jointthat has an intermetallic layer around 1micron thick, which is considered optimalfor maximum electrical performance andphysical reliability. Figure 1 also focuses

on energy transfer as the mechanism thatdrives a temperature rise. This analysisdemonstrates how the soldering iron’sproperties influence a series of solderjoints getting formed.

When the soldering iron tip first comesinto contact with the pad, thermal energystored in the tip is transferred to the joint’ssite. As this stored energy is dissipated, thesoldering iron heater becomes the mainsource of energy necessary to form thejoint. Efficient delivery of heater energy,through the main body and face of the tip,will lead to rapid melting of the solderalloy as its temperature increases.

This energy-flow model highlights twoimportant aspects of the soldering iron’sperformance. First, the thermal propertiesof the tip, including its mass, dimensions,and constituent materials, are crucial in de-livering the heater energy to the site of thejoint to be created. Second, the heater mustrespond quickly to the sudden applicationof a thermal load, so that the joint can at-tain the recommended temperaturequickly and smoothly without experiencingexcessive temperature drop or overshoot.

Examining the performance of com-mercial soldering irons shows appreciabledifferences between indicated tempera-ture and actual tip temperature during thecreation of a soldered joint. This can pre-vent operators from meeting the condi-tions recommended in applicable solder-ing standards, leading to the risk ofsubstandard or rejected joints.

Tip Characteristics

Clearly, the tip’s size and shape has animportant influence on heat-transfer effi-ciency. If the tip has low thermal masscompared to that of the joint, the amountof stored energy will be low, and the initialtemperature rise will be slow. If the facesize is insufficient to ensure a suitable con-tact area with the solder joint, the transfer

of stored energy and heater energy will beimpaired, which will also act to slow downthe rate of temperature rise.

Figure 2 shows the effect of choosingan incorrect tip that maintains 50% con-tact with the joint, resulting in failure toreach the IPC-recommended solderingtemperature. During the heater-powerphase, the length and width of the tip willdetermine how efficiently the heater en-ergy can be conducted to the tip face.

Hence, if the tip is long and thin with alow thermal mass and a small face sizecompared to the joint, its ability to deliverthermal energy to the site of the joint willbe low. This will result in a slow tempera-ture rise, leading to slow joint formation.

An over-large tip is also undesirable.Excessive stored energy may damage theprinted circuit board pad, and a face sizethat is too large may result in bridging. Se-lecting a suitable tip size for the operationat hand is important if operators are toproduce large numbers of acceptable sol-der joints at a high rate of throughput.

The tip-plating thickness also has anappreciable effect on the transfer of en-ergy. A thick plating may be applied to ex-tend the lifetime of the tip, but it will neg-atively influence thermal conductivity. Theshape of the tip affects thermal perform-ance as well. Some tips on the market areunnecessarily stylized; for example, withvarious flats, step downs, and constrictionsalong the length. These may look attrac-tive, and in some cases serve a minor func-tional purpose, but they actually restrictthe thermal performance of the tip.

The best possible tip shape is not ex-cessively long, is smoothly tapered, has achisel-shaped face that should be matchedin size to the joint, and does not have ex-cessive plating thickness. It should havesufficient mass to help deliver the neces-sary energy into the thermal load to raisethe solder alloy above its melting pointwithin an acceptable time.

Based on information from OK International, Garden Grove, Calif., www.okinternational.com.

Tips for Creating Consistency in Soldering

Solderers can achieve lower defect rates by paying attention to key elements,including temperature control and energy flow from the soldering iron to the joint

OK International B and S Feature March 2011:Layout 1 2/8/11 8:13 AM Page 60


61WELDING JOURNAL

Many operators expect to use only onesize and type of tip while soldering. In prac-tice, having the freedom to choose a differ-ent tip for certain tasks will enable opera-tors to accelerate good joint production.

Heater-Control Strategy

Assuming the operator has chosen theoptimum tip for a given sequence of sol-dering tasks, solder joint formation de-pends on effective management of theheater power. Bearing in mind the role ofthe tip, implementing a heater with higherwattage — rather than setting a higher tiptemperature — is the most effective wayto quickly raise the solder to its moltenstate. In addition, the tip will experience asmaller temperature drop when applied tothe load, and it will also recover its normaloperating temperature more quickly aftercompletion. Both of these factors are im-portant if operators are to produce largenumbers of high-quality solder joints inrapid succession.

Ensuring adequate heater power forthe range of soldering tasks to be per-formed is a prerequisite. However, con-trolling that power is vitally important ifother hazards such as potentially damag-ing thermal overshoot are to be avoided.

If the heater has a fixed power rating,this will impair its ability to provide suit-able control. It can only operate at itsrated power to maintain the preset tiptemperature as energy is transferred fromthe tip to the solder joint. In addition, thetip-temperature sensor is usually locatedin the main body of the soldering iron,away from the face. It will always suffer

from some inherentlag as the tip tem-perature fluctuates.

A soldering ironstation with a built-in digital tempera-ture meter may ap-pear to offer asolution. The usercan preset the oper-ating temperatureand test that the tipmatches this presetvalue by touchingagainst a built-in testpoint. Many produc-tion managers be-lieve this offers a sat-isfactory assuranceof correct solderingiron adjustment andexpect the tool will deliver repeatable per-formance on the factory floor. The loadplaced on the soldering iron during such atest is appreciably lower than that imposedduring a soldering operation. It’s essen-tially a static test that, in practical terms,simply confirms the calibration of the tip-temperature sensor against that of the testsensor. The operator can gain no repre-sentative information regarding how thesoldering iron will perform when workingto complete a sequence of, for example,eight or more solder joints performed inrapid succession.

Under thermal load, the temperatureof a typical soldering iron tip can be shownto diverge markedly from that indicated bythe digital temperature gauge. Fitting athermocouple close to the end of the tip

and recording its response in relation tothe digital temperature gauge during a sol-dering operation has produced the resultsshown in Fig. 3. This shows a large drop inactual tip temperature as the tip is placedon the joint. The instrument’s digital tem-perature indicator does not show thisdrop. The temperature reading is dampeddue to the action of the sampling and av-eraging circuitry placed between the tip-temperature sensor and gauge.

In addition, Fig. 3 shows an appreciabletemperature overshoot as the heater con-trol overcompensates for the detected fallin tip temperature. Because the recom-mended temperatures and time periods in-dicated in the soldering standards do nottake such oscillations into account, thesecan result in substandard joints or will slow

Fig. 1 — The Pb-Sn vs. Sn/Ag/Cu (SAC) process window shows en-ergy transfer from the soldering iron into the connection, to heat thejoint to a temperature suitable for soldering.

Fig. 2 — Selecting an incorrect tip that maintains only 50% contactwith the joint results in failure to reach the IPC-recommended sol-dering temperature, as shown in the tip face to pad face area graph.

Fig. 3 — This undershoot and overshoot outcome is from a solder-ing operation fitting a thermocouple close to the tip’s end and record-ing its response in relation to the digital temperature gauge.



MARCH 201162

down joint formation with a correspondingeffect on productivity. A temperatureovershoot carries the potential to damagethe board or component, and in any case,indicates below-optimal process control.

Manage Energy,Not Temperature

The key to the problem lies with thefact that temperature-controlled solder-ing irons are philosophically not designedto manage thermal energy. Instead, theheater, which is usually ceramic, is turnedon if the embedded temperature sensorreads too high and off if the sensor readstoo low. In practice, when the heater con-troller receives the signal to turn on, thetip temperature will have already fallenbelow its set point. The heater is then runat its maximum power to increase the tiptemperature and will invariably cause thetemperature to overshoot.

As an alternative to a conventionalthermostatically controlled heater, induc-tive heating allows the maximum temper-ature of the tip to be governed withoutusing temperature-sensing or control cir-cuitry. An inductive heater suitable for usein a soldering iron comprises a copper slugcoated with magnetic material, which iswound with the current-carrying coil toform the heater. The properties of themagnetic coating can be adjusted so thatits Curie temperature coincides with the

preset maximum temperature for the sol-dering iron. At the Curie temperature, thecoating loses its magnetic properties sothat the inductive heating action ceases.The temperature of the slug can neverovershoot this natural maximum. When athermal load is applied by placing the ironon the solder joint, the slug falls below theCurie temperature, and the coating beginsto reacquire its magnetic properties. In-ductive heating is then reactivated. In thisway, an inductive soldering iron heater isnot only able to operate without a tem-perature sensor or control circuitry, but italso recommences supplying thermal en-ergy automatically, as soon as the tip isplaced in contact with the joint. The tiptemperature is effectively capped and cannever overshoot the preset maximum.

Speed and Cost

As a practical comparison betweentemperature control and thermal-energymanagement, consider a soldering com-parison between a conventional solderingiron and an inductively heated unit. Figure4 compares the time taken by both irons toproduce a series of nine solder joints.Thermocouples were inserted into the tipsof both soldering irons, close to the tipface, to monitor the temperature of eachtip continuously and in real time. The con-ventional soldering iron takes longer to re-gain its preset temperature as the test pro-

gresses. In contrast, the enhanced energy-management capabilities of the induc-tively heated iron enable a more consis-tent production rate and does not sufferfrom temperature overshoot.

The slowdown in joint production overthe course of this demonstration translatesinto a productivity loss, leading to highercosts for operators. Measuring the extratime taken to complete the test allows anestimation of the additional business cost.This is more than the purchase price of asoldering iron station and can also exceedthe cost of an entire extra operator.

Assuming an operator works a total of2000 h in 50 working weeks of 40 h, and30% of that time is spent performing handsoldering, this equates to 600 h of solder-ing time using the fastest soldering irondescribed in Fig. 4. Since the next fastesttool is 18% slower, the operator will takean extra 108 h to complete the same work.Assuming a total burden cost of labor at$14.50/h (keeping in mind real figures varydepending on geographical location), thiscorresponds to $1711. If ten operators areemployed, all using the slower equipment,the cost to the corporation is $17,110.

The same estimate applied to the nextslowest soldering iron reveals an evenlarger loss. Because this unit is 39%slower, the extra cost of having ten opera-tors working at this enforced lower ratewill be $33,785.

This calculation shows that businessescan quickly recoup the larger capital in-vestment to acquire better performing sol-dering irons. In some cases, the savings canexceed the cost of employing an additionaloperator. To consider the total ownershipcost of the soldering process, including thecost of consumables as well as lost produc-tivity due to unsatisfactory productionquality, underpowered soldering irons dis-playing poor energy control represent aneven greater cost to the enterprise.

Conclusion

Control of the soldering temperature isan adequate strategy when performingisolated soldering operations at a low rateof repetition. In a practical production en-vironment, where high throughput andproductivity are required, fast and effi-cient transfer of thermal energy is re-quired. This can be achieved through op-timum tip selection and by ensuringaccurate management of heater powerwithout exceeding the temperatures recommended in established solderingstandards.♦

Nine Load Test: Speed to Recovery

Inductively heated unit

Conve

ntion

al

solde

ring

iron

1

Conve

ntion

al

solde

ring

iron

2 Inductively heatedunit

Conventionalsoldering iron 1

Conventionalsoldering iron 2

Conventional soldering iron 2 (750F) Conventional soldering iron 1 Chisel 2.4mm (769F) Inductively heated unit

Fig. 4 — The speed of an inductively heated unit vs. two conventional soldering irons is meas-ured in making nine solder joints.



MARCH 201164

TECHNOLOGY NEWSLow-Melting Aluminum BrazingAlloys of the Al-Si-Zn System

Brazing aluminum alloys with stan-dard filler metals of the Al-Si system iscarried out at 600°–620°C, which is closeto the solidus temperature of base metals.Therefore, applications and testing oflow-melting brazing filler metals to avoidoverheating of base metals is the focus ofmany industry efforts.

New filler metals of the Al-Si-Zn sys-tem having melting ranges from489°–515°C to 568°–572°C were devel-oped and tested at Leibniz UniversityHannover, Germany (Ref. 1). The follow-ing two alloys exhibited better mechanicalproperties than others: Al-5.9Si-37.6Znwt-% having a melting range of480°–530°C, yield strength 345 MPa, andelongation 7%; and Al-9.3Si-16.2Zn wt-% having a melting range of 540°–557°C,yield strength 205 MPa, and elongation12%. It’s important to note that the plas-ticity of these brazing alloys is the same asthe plasticity of the standard Al-12Si fillermetal, while the strength of three-compo-

nent Al-Si-Zn alloys is at least 50% high-er than that of Al-Si eutectic alloy. Newfiller metals can be manufactured in wireform, as well as any performs made fromthe wire.

Corrosion resistance of new filler met-als was also measured in a potassium chlo-ride solution using the standard Ag/AgClelectrode. The corrosion potentials of newfiller metals (–1400 and –1380 mV) areclose to that of the standard Zn-5Al sol-der (–1480 mV) and better than that ofthe Al-12Si brazing alloy (–960 mV).

A Nanocomposite Mo-Ni FillerMetal for Brazing Molybdenum toMo-Re Alloy at 1350˚C

Furnace brazing of molybdenum andMo-47.7Re alloy using the Mo-53.5Ni(wt-%) filler metal doped with molybde-num or nickel nanoparticles was investi-gated at University of Kentucky,Lexington, Ky., and the brazed jointswere characterized in comparison withnondoped braze (Ref. 2). The furnaceatmosphere used was a mixture of 25%

N2 and 75% H2. Five different filler com-positions were tested containing 0%nanoparticles; 1, 3, and 5% of Mo + Ni(50/50) nanoparticles; as well as 5% ofMo nanoparticles.

Nanocomposite brazing filler metalsfeatured similar joint formation vs. thenondoped brazes. However, the differ-ence was attributed to spreading charac-teristics of nanocomposites vs. virgin liq-uid filler metals. The melting point ofnanocomposite is suppressed vs. the caseof noncomposite. Spreading of nanocom-posite filler metals is more pronouncedthan that of noncomposite fillers. Filletsbetween Mo base and Mo-Re appearlarger, while no significant difference injoint fillet formation was noticed withinthe capillary gap along the Mo-Re seamoverlap. A hypothesis is formulated thatdoping the brazes with small amounts ofnanoparticles may offer a better flow con-trol of molten composite filler metal. Theaddition of nanoparticles changes rheo-logical properties of the braze material,but it also impacts the spreading at thepeak brazing temperature.

For info go to www.aws.org/ad-index

B and S Technology News March 2011:Layout 1 2/9/11 2:51 PM Page 64


65WELDING JOURNAL

TECHNOLOGY NEWSEffect of Process Parameters onShear Strength and ResidualStresses of Diamond-SteelJoints Brazed with a CuSnTiZrFiller Metal

The correlation between microstruc-ture, residual stresses, and shear strengthof diamond-steel joints subjected to differ-ent brazing conditions, i.e., brazing tem-perature and dwell time, was studied by theteam of EMPA, Dübendorf, Switzerland(Ref. 3). The active brazing filler metal Cu-14.4Sn-10.2Ti-1.5Zr (wt-%) was used tobraze monocrystalline, block-shaped dia-monds to a stainless steel substrate. Thebrazing parameter variations comprise thefollowing three temperatures: 880°, 930°,and 980°C at 10 or 30 min holding time.

The microstructure of brazed jointscharacterization revealed a (Cu,Sn)matrix with different intermetallic phases.An intermetallic layer of the Fe2Ti phasewas formed at the steel-joint metal inter-face, as well as polygonal crystals of thesame composition in front of it. Thethickness of the (Fe,Cr,Ni)2Ti interlayerand diffusion zone increased with higherbrazing temperature and longer holdingtime. Both the interlayer and crystalsgrow with increasing brazing temperatureand extended dwell duration. The jointsbrazed at 980°C exhibited tensile residualstresses of the maximum value 150 MPa,whereas the joints brazed at 880° and930°C had compressive residual stresseswith a maximum value of –350 MPa. Theshear strength also strongly depends onbrazing parameters; it goes down from321 MPa at 880°C, 10 min and 221 MPa at880°C, 30 min to 78 MPa at 980°C, 30 minand 71 MPa at 980°C, 10 min.

A significant difference was also foundin fracture behavior. Both fracture sur-faces on steel and diamond sides, of thejoints brazed at 880°C, had smooth spotsidentified as a TiC interlayer interspersedwith rough spots that are sheared fillermetal. Completely different shear sur-faces were found for the joints brazed at980°C. The whole surface is smooth, indi-cating that the fracture occurred directlyalong the joint metal-diamond interface.

Neutron Imaging as a Method ofNondestructive Examination ofStainless Steel BrazedComponents

The method of nondestructive exami-nation (NDE) of stainless steels and nickel

superalloy brazed joints, developed inNeutron Imaging and Activation GroupPaul Scherr, Villigen, Switzerland, is suit-able for components manufactured inaerospace, gas turbine, and automotiveindustries (Ref. 4). One problem in themanufacture of these components is theabsence or limitation of NDE, such as X-

rays, because the contrast of the joint metaldoes not differ much from the base metal.The new imaging method is based on ther-mal neutrons that offers the NDE possibil-ity of joints brazed with boron-alloyed nick-el filler metals, e.g., AWS BNi-2.

Components of heat exchangers, con-centrical pipes, and Dewar cane — made

Aerospace Grade

Brazing & Welding

Alloys

Aerospace Grade

Brazing & Welding

Alloys

Aimtek is proud to offer a variety of value-added services from

custom labeling, to specialized packaging, to onsite equipment

training. Our technical Engineering Department and knowledgeable

staff will help meet your standard and custom requirements from

concept to production. We understand that a small request can

make a big difference.

• Powder and Paste

• Wire and Foil

• Rings and Preforms

• Cut Length Rods

IN STOCK and waiting for you!




MARCH 201166

TECHNOLOGY NEWS

of stainless steels 304L and 316L, nickelalloys Inconel® 600 and Nimonic 75, andcopper — were tested. A pronouncedcontrast for brazed joints was obtaineddue to boron, a strong neutron-absorbingmaterial, while base metals are rathertransparent for thermal neutrons. Boththe radiographic images in 2D and tomo-graphic reconstructions in 3D providedinformation about the filler metal distri-bution in the joints.

The initial fast neutrons (energyaround 1 MeV) were emitted from thefission process in the reactor core or spal-lation process using a target. The neu-trons have the advantage to penetrate0.40-in.-thick layers of metals, and objectdimensions up to 300 × 300 mm (12 × 12in.) can be inspected. Impressive picturesof brazed joints and whole brazed partswere presented to demonstrate the capac-ity of a new NDE method.

Effect of Natural Aluminum OxideFilm on Thermal Joining

Dense and high-melting aluminumoxide film should be removed from the

Brazing Aluminum Should Be Easy. Now It Is !!

Innovative Solutions For

Brazing Aluminum

Multiple Alloys

-Corrosive Fluxes

ChannelFlux is a patented technology and registered trademark of Bellman-Melcor, LLC

Bellman-Melcor, LLC 800-367-6024 www.channelflux.com www.bellmanmelcor.com



B and S Technology News March 2011:Layout 1 2/9/11 2:51 PM 6


67WELDING JOURNAL

base materials during brazing to providewetting and flow of filler metals. Vacuumor many fluxes are used for this purpose.However, the influence of the site condi-tions or climate effect (e.g., during thestorage and transportation) on the com-position and structure of alumina filmwere not yet studied. The team ofTechnische Universität Dresden and BehrGmbH & Co., Stuttgart, Germany, inves-tigated the growth and structure of alumi-na film on the base Alloy A3003 and itsbehavior during flux brazing with theA4045 as the filler metal (AWS BAlSi-5)depending on different conditions of thebase metal oxidation. Applications ofXPS and Fourier Transformed InfraredSpectroscopy (FTIR) permitted to studya few nanometers thick oxide or hydrox-ide films in situ and brazing experiments(Ref. 5).

Holding the base metal A3003 in dryair at 23°C (50% humidity) does notaffect the oxide film on the surface.Increasing the air temperature to 40°Cand humidity to 92% resulted in signifi-cant growth of the oxide film thicknessfrom 4 to 8 nm. Further increase of

TECHNOLOGY NEWS



B and S Technology News March 2011:Layout 1 2/14/11 8:09 AM Page 67


MARCH 201168

humidity to 100% (a condensation state)at 23°C resulted in a growth of the alumi-na film thickness by 50% for 9 days.

The brazeability test confirmed a sig-nificant effect of storage and climate con-ditions on wetting and flow of the brazingfiller metal BAlSi-5 on the surface ofA3003 base metal. The brazeability after50 days in dry air (50% humidity) was esti-mated as 98%; the brazeability after 9 daysin wet air (92% humidity) or after 3 days at100% humidity (condensation) was 79%;and finally, after 9 days at 100% humidity,the brazeability was estimated as only 5%.

Active Soldering of Copper withAl2O3, ZrO2, and AlN Ceramics

Ultrasonic soldering of Al2O3, ZrO2,and AlN ceramics with copper (bothceramic-to-ceramic and ceramic-to-metal combinations) using the lead-free,active solder Sn-4Ag-2Ti-0.5Y was inves-tigated at Beijing University ofTechnology, People’s Republic of China,and soldered joints were characterized bytesting shear strength and studyingmicrostructure (Ref. 6).

The results indicted that all solderedjoints were fractured in the zone of interface between ceramic and joint metal. Shear strength of alumina-to-alumina joints was about 38 MPa, whilethat of alumina-to-copper joints was 34MPa. Shear strength of zirconia-to-zirco-nia joints was about 35 MPa, while that ofzirconia-to-copper joints was 40 MPa.Shear strength of AlN-to-AlN joints wasabout 31 MPa, while that of AlN-to-cop-per joints was 34 MPa. Application ofultrasonic vibrations allowed obtaining agood quality of soldered joints withoutvoids. No intermetallic compounds werefound at the ceramic-solder interface,while expected Cu3Sn and Cu6Sn5 com-pounds were formed at the copper-solderinterface. The microstructure of solderedjoints typically comprised the followingfive phases: 1) the matrix Sn-4Ag, 2) theblock-shaped Ag3Sn phase distributed inthe matrix, 3) the lath-shaped β–Ti6Sn5phase, 4) particles of α-Ti + Y5Sn3 phase,and 5) black particles of the SnAgYphase. However, all these structural com-ponents do not affect the strength of sol-dered joints.

Combined Induction-UltrasoundSoldering of Aluminum MatrixComposites

A growing demand for metal matrixcomposites in the industry requires devel-opment of new reliable methods for join-ing. Soldering, as a low-temperatureprocess, is especially attractive due to adestructive effect of heating on the struc-ture of aluminum matrix composites. Anew soldering technology includinginduction heating assisted with ultra-sound vibration was developed and testedat Technische Universität Chemnitz,Germany, for joining aluminum matrixcomposite A2017 + 5/15 vol-% (Al2O3)pusing Zn-5Al solder and a composite sol-der containing Sn-3Cu or Sn-3.5Agmatrix with 35 vol-% of alumina or SiCparticles (Ref. 7). This is a flux-free sol-dering process due to application of ultra-sound activation. Soldering with the Sn-based composite solder was made at280°C for 190 s and with the Zn-5Al sol-der at 400°C for 110 s.

Dense, quality joints were obtainedwith both previously mentioned solders.

TECHNOLOGY NEWS

April 22-25, 2012 • Red Rock Casino Resort Spa • Las Vegas, NV USA

the world of brazing and soldering.

IBSC First Announcement and Call for Papers

ASM International® and the American Welding Society organize this four-day technical event. Recognized by industry professionals as the world’s premier event for the brazing and soldering community, IBSC brings together scientists and engineers from around the globe involved in the research, development, and application of brazing and soldering.

Present your research at the premier event for the community.Abstract Deadline: July 1, 2011

Be part of the future of brazing and soldering technology. Plan to attend IBSC 2012 in Las Vegas.

A Conference Proceedings will be published.

Visit www.asminternational.org/ibsc for the latest conference information.



69WELDING JOURNAL

However, soldering assisted with ultrasound resulted in erosionof the base metal. Reinforcing alumina particles were partiallytransferred from the base material to joint metal. Tensilestrength of soldered joints of the A2017 + 15% (Al2O3)p com-posite made using Zn-5Al solder was in the range of 50–70 MPa,while that of the A2017 + 5% (Al2O3)p composite was only20–40 MPa. The tensile strength of joints manufactured with theSn-3.5Ag + 5%(Al2O3)p solder was 14.5 and 12 MPa for thesame base materials.

Nanoparticle-Assisted Diffusion Brazing ofStainless Steel

Transient liquid phase diffusion brazing is widely used forjoining stainless steels to a variety of materials such as superal-loys, titanium alloys, copper alloys, and low-alloy steels.Particularly, electroplated nickel-phosphorous NiP interlayershave been used to diffusion braze stainless steels and nickelsuperalloys. In the study made by scientists from the School ofMechanical, Industrial, and Manufacturing Engineering, OregonState University (Ref. 8), stainless steel 316L laminae were dif-fusion brazed with an interlayer of nickel nanoparticles (NiNP)and compared with samples joined by conventional diffusionbonding and electroplated nickel-phosphorous diffusion brazing.Comparison was made with regard to microstructural evolution,diffusional profile, and bond strength. All bonding was carriedout in a uniaxial vacuum hot press at 1000°C with a heating rateof 10°C/min, a dwell time of 2 h, and a bonding pressure of 10MPa.

Bond strength measurements showed that the sample brazedwith a nickel nanoparticle interlayer had the lowest void fractionat 4.8 ± 0.9% and highest shear strength at 141.3 ± 7.0 MPa,while the maximum shear strength measured before the bondfailure for diffusion bonded and NiP-brazed samples were 121.6± 12.0 MPa, 114.7 ± 11.0 MPa, respectively. The improved shearstrength in the NiNP samples was explained by a combination oflarger cross section, i.e., lower void fraction, better shaped voids,and lack of brittle secondary phases.

Based on fracture surfaces, the fracture mechanism for thediffusion bonded and NiNP diffusion brazed samples was ductiledue to the cup and cone formation clearly seen on the surface.The cup and cones are much larger in the NiNP sample, suggest-ing greater ductility.

Wavelength dispersive spectroscopic analysis of sample crosssections showed substantial diffusion of Ni and Fe across thenickel nanoparticle bond line. Scanning electron micrographsshow no secondary phases along the nickel nanoparticle bondline.

Refs. 1–7 are abstracted from the 9th International Brazing &Soldering Conference held in Aachen, Germany, June 2010, DVS-Berichte.

1. Bach, Fr.-W., Möhwald, K., Holländer, U., and Langohr, A.Low melting aluminum brazing alloys of the system Al-Si-Zn, v.263, 117–121.

2. Busbaher, D., Liu, W., and Sekulic, D. High temperaturebrazing of Mo/Mo-Re with a nano-composite Mo-Ni filler, v. 263,211–214.

3. Buhl, S., Leinenbach, C., Spolenak, R., and Wegener, K.Microstructure, residual stresses and shear strength of diamond-steel joints brazed with CuSnTiZr filler alloy as a function ofbrazing parameters, v. 263, 243–247.

4. Grünzweig, C., Lehmann, E. H., Hartmann, S., and Haller,M. Neutron imaging: A nondestructive testing method forbrazed components using boron-alloyed nickel braze filler, v.263, 274–278.

5. Zähr, J., Füssel, U., Ulrich, H. -J., Türpe, M., Grünenwald,B., Wald, A., and Oswald, S. Influence of the natural aluminumoxide coat on thermal joining, v. 263, 296–303.

6. Qu, M., Li, H., Zhang, Z., and Zhuang, H. Active solderingcopper with ceramics, v. 263, 320–323.

7. Wielage, B., Hoyer, I., and Weis, S. A combined induction-ultrasound process for joining aluminum matrix composites, v.263, 352–357.

8. Tiwari, S. K., and Paul, B. K. 2010. Comparison of nickelnanoparticle-assisted diffusion brazing of stainless steel to con-ventional diffusion brazing and bonding processes. Journal ofManufacturing Science and Engineering, June, vol. 132/030902-1to 030902-5.

TECHNOLOGY NEWS


Information provided by ALEXANDER E. SHAPIRO([email protected]) and LEO A. SHAPIRO, Titanium Brazing, Inc., Columbus, Ohio.


tips for creating consistency in solderingsome tips on the market are unnecessarily stylized; for...

Documents