A L P H A
ExactalloySolder preforms
for product and process improvement
™ExactalloySolder preforms
for product and process improvement
™
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There is anExactalloy™
preform inthe rightshape andsize toimproveyour assemblyoperation,product reliabilityand quality.
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C O O K S O N E L E C T R O N I C S
Exactalloy™ solder preformsare the ideal solution to high-volume, precision-solderingprocesses in electronic assem-blies, sealed lighting, filteredconnectors, multiple leadedconnectors, component manu-facturing and the plumbingindustry.
What are preforms?
Preforms are precisely formedpieces of solder, produced inlarge quantities with very tighttolerances. There are almostunlimited combinations of different preform shapes,sizes, combinations of solderalloys and flux delivery systems.
Preforms are commonly formedin 63/37 tin/lead solder. Bothlower melting point and highermelting point alloys are alsoavailable. See the Soft SolderAlloys table on page 10 for alist of the most common alloysused to produce Exactalloy™
preforms. Some solder alloyscannot be used to producesome preform shapes. Highbismuth alloys, for example,can be very brittle, and cannotwithstand rolling and stamp-ing processes required to formsome shapes.
A wide range ofdesign choices
Exactalloy™ preforms are avail-able in sizes from 0.020" to2.00" (squares, discs or washerOD). Thickness can range from.004" to 0.25". Generally, fluxadd-on represents .5% to 2.5%by weight of the preform.
Improved qualityand performance
Cookson Electronics AssemblyMaterials’ experienced repre-sentatives are ready to workdirectly with your designers to recommend solder preformsto provide maximum assemblyefficiency, product quality, andimprove your manufacturingprocesses.
We can furnish Exactalloy™
preforms in discs, rectangles,squares, rings, washers, sleevesand washer arrays (linked preforms). Your CooksonElectronics technical repre-sentative can help you specifythe size and shape to achievethe maximum benefit for yoursoldering process.
Custom shapes can also beproduced to match specificapplications. Tooling chargesmay apply to custom shapesand sizes.
Both X-ray diffraction and wet analysis methods are
used to assure that every lot of Exactalloy™ preforms
meets or exceeds the metallurgical requirements of the
IPC and the customer.
Opposite: Exactalloy™ preforms can
be produced in thousands of shapes
and sizes, solving even the most
difficult soldering design challenge.
Each batch of Exactalloy™ preforms
is carefully examined under
magnification to assure compliance
with dimensional requirements.
Cookson Electronics' uniqueflux coating process offers twodistinct advantages over fluxfilled preforms: a flux-coatedExactalloy™ preform deliversflux to the area to be solderedwhen it is needed most — justbefore the solder is melted, andflux-coated solder is protectedfrom oxidation. Oxide-free solder yields better wettingand joint strength, and caneliminate the formation ofcold solder joints that canhave a severe impact on prod-uct reliability. Flux coating islimited to preforms at least.007" (0.18 mm) thick. Thinnerpreforms may lose their shapein the fluxing process. Seechart for available flux options.
Available Flux TypesFLUX TYPE INTERNAL EXTERNAL
RMA (ROL1) yes yes
RA (ROM1) no yes
NC (ROL0) yes yes
RSA (ROH1) no yes
WS (ORL0) yes no
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Precise control of foil thickness is a critical
step in providing the exact volume of solder
required. Here, linked arrays are used to
eliminate hand soldering on multiple-row
connector sets. Preforms also provide
more solder volume, eliminating
inefficient paste-in thru-hole processes.
There are numerous exampleswhere the use of Exactalloy™
preforms can optimize one or both of the common mass soldering techniques.
Eliminate hand soldering
The use of preforms can pro-vide a more consistent qualityalternative to repetitive handsoldering applications. If corewire is being used to hand solder multiple leaded connec-tors, or to solder a non-planararea in a circuit assembly, preforms often offer a bettersolution.
Exactalloy™ preforms deliverthe exact volume of solderrequired. They can be placedexactly where needed, andmultiple solder joints can bereflowed simultaneously usinga heat gun, or a reflow oven.Low melting temperature preforms are commonly usedto eliminate disturbance ofother solder joints alreadyformed on the assembly.
High-temperature preforms canbe used if the hand solderingassembly is being performedbefore conventional SMT orwave soldering processes.10/88/2 (Tin/Lead/Silver) or96/4 (Tin/Silver) are commonchoices for this application.See the Soft Solder Alloystable on page 10.
Paste-in thru-hole
Problem: In an attempt toeliminate wave soldering,many assembly processes usesolder paste to solder thru-holecomponents. The goal is toeliminate wave soldering, andsubsequent thermal stressresulting from multiple solderreflow cycles.
Solder paste is very difficult tostencil over an open hole, anddispensing adequate volumesof paste can be just as chal-lenging. Thick, multiple layerboards also make paste inthru-hole processes moredifficult. Per IPC Standard B610, at least 75% of the spacebetween the lead pin and thehole must be filled with solder.
Solution: The use of Exactalloy™
washers or linked washerarrays eliminates the inherentproblems of delivering enoughsolder to meet the IPC standard.The design of the preformbegins with the inner diameterof the washer. It should be 0.002" to 0.005" larger thanthe OD of the lead pin. The
next consideration is thediameter of the thru-hole orvia. The OD of the Exactalloy™
washer must be at least .005"greater than the diameter ofthe hole. The limit of the ODis usually the diameter of thepad surrounding the platedthru-hole.
Given the ID and the OD,Cookson Electronics can man-ufacture the washer to anythickness from .004" to a limitof 110% of the ID. Using thistechnique, Exactalloy™ preformscan be engineered to meet orexceed the IPC standard.
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Exactalloy™ preform solutions provide a wide range ofadvantages in electronic circuit assembly applications.
Above left: Cladded discs provide
a simple method of soldering very
large components from the opposite
side of the board.
Top right: Cookson Electronics can
package preforms on tape and reel
for use with common pick and
place equipment.
Left: Our extensive engineering
capabilities can turn your ideas into
high-production reality. Bimetallic
solder sleeves are but one example
of Cookson Electronics’ ability to
engineer solder fabrication.
Step stenciling
Problem: In some SMT assem-blies, larger volumes of solderare required on one or moresurface mount pads. Traditionalco-planar paste stenciling willnot yield the solder volumerequired. In this case, theprocess engineer has twochoices, neither of which maybe acceptable: stencil morepaste onto the required padsor use a second dispensingprocess. The dispensing optionis often impossible in finepitch applications.
Solution: Place an Exactalloy™
solder preform segment(square or rectangle) into thestenciled paste. Exactalloy™
preforms are available in tapeand reel packaging. The pre-form is sequenced in yourpick and place process to bepositioned prior to placementof the SMT component desig-nated for that pad.
Simply sequence the preformplacement prior to the compo-nent requiring the additionalsolder volume.
C O O K S O N E L E C T R O N I C S
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Reduce or eliminatewave soldering
Problem: The primary assemblyprocess used is SMT. Thereare still one or more thru-holecomponents on the assemblywhere the board must be runthrough the wave to assure a complete solder joint. The second thermal cycle maydamage some of the paste joints.Eliminating wave solderingwill reduce the cycle time ofeach assembly.
Solution: After the paste hasbeen stenciled, and all of theSMT components have beenplaced, use a semi-automatictechnique to position flux-coated preform solder washerson the thru-hole componentleads. This completely elimi-nates the wave soldering step,increasing the production rateand reducing rejects. (See theconnector jig schematic, onopposite page.)
Sealed beam lighting
As the leader in lead (Pb) freesoldering, Cookson Electronicshas developed several alloysthat exceed today’s require-ments for the elimination oflead, which is the trend in thisindustry. Both flux-coatedwashers and flux-cored seg-ments are used to automatethe placement of solder insealed beam lighting.
Flux-filled and flux-coated lead-free
solder preforms are used by the
major automobile lighting producers
to deliver the exact amount of solder,
in exactly the right shape, exactly
where it is needed.
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Exactalloy™ preforms deliverexactly the right amount ofsolder, in the exact alloy, everytime. Consistent, reproduciblesoldering is the real benefit tothe lighting industry.
Connectors
Filtered and ShieldedConnectorsExactalloy™ preform washersare made in both a single alloy,and in laminated layers of abase metal and solder. A typicalapplication is attaching a ferriteEMI shield to a connector pin.The pin is suspended in themiddle of the ferrite tube bythe unmelted base metal. Thesolder layers on either side ofthe base metal form the solderjoint. Similar technology isused to produce RFI shieldedconnector leads. CooksonElectronics’ lead-free alloysand flux-coating processes
See how Exactalloy™ preforms are providing innovativesolutions in actual applications.
Component manufacturing
CapacitorsPreforms are used in both surface mount and thru-holecomponent manufacturing.Both axial and radial leadedcapacitors are manufacturedusing solder preforms. A hightemperature alloy (Sn 95/Ag 5,Sn 10/Pb 88/Ag2, Sn 5/Pb 85/Sb 10) is typical, to eliminatesolder reflow when the capaci-tor is soldered to the final circuit assembly. High temper-ature alloys allow for the useof thermal curing encapsulentsas well.
Soldering lead frames toceramic capacitor bodies withflux-coated Exactalloy™ pre-forms can eliminate problemsassociated with the use of solder paste. Preforms alsooffer the additional advantagesof delivering reproducible volume, eliminating fluxresidue, increasing productionspeed and producing fasterreflow cycle times.
provide an unlimited numberof beneficial solutions for theconnector manufacturer.
Pre-Soldered ConnectorsExactalloy™ preforms can beautomatically placed on con-nector leads, and the resultingconnector requires no addi-tional paste or thru-hole sol-dering by the connector user.Your Cookson Electronicstechnical representative canshow you several methods ofapplying preforms to multiplepin connectors.
Attaching Coaxial ConnectorsHand soldering can be elimi-nated as a high volume methodof soldering coaxial connectorsto cable ends. Several uniquesolutions have been developedby Cookson Electronics forattaching solder sleeves to barewire ends. Coaxial connectorscan be slid over the preformring, followed by inductionreflow of the solder. Flux-coated sleeves make thisprocess highly efficient andreproducible.
Hundreds of solder washers can
be placed automatically by using
fixtures. Your Cookson Electronics
technical representative can help
you design a fixture for rapid place-
ment of flux-coated washers on
multiple-pin assemblies.
C O O K S O N E L E C T R O N I C S
Automatic placement of preforms
is often the key in reaping the
efficiency offered by automatic
soldering. In this application, a
bowl feeder dispenses flux-coated
washers for subsequent placement
and reflow.
TOP VIEWOF FIXTURE
CROSS SECTIONOF FIXTUREØ Hole = Ø Washer+0.15mmLength hole = Washerthickness +25%
Preform washers aredropped into fixture.
Connector is placed in fixture allowing preformsto attach to connectorpins.
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Using a solder preform to coatthe surface mount contactswith solder in chip scalecapacitors eliminates dippingheat-sensitive ceramics intohigh melting point solder baths.
ThyristorsExactalloy™ preforms are theideal metal to metal, and metalto diode joining material. Hightemperature alloys are used toeliminate solder reflow duringthe coating and curing of epoxyencapsulents. Flux-coatedExactalloy™ preforms (discs,rectangles or squares) are ideal for this application.
RectifiersDiode attachment with thesuitable preform alloy choicemakes high volume productionpossible.
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Optoelectronics
Indium-based alloys affordexcellent ductility, gold scav-enging resistance, and lowtemperature soldering (whereneeded) in this rapidly evolv-ing market. Indium’s ductilityallows for soldering materialwith large differences in theircoefficient of thermal expansion.Cookson Electronics’ technicalservice personnel will helpyou specify the best alloy andpreform to improve yourapplication.
Hybrid Circuits
Solder based fuses are used to protect high temperaturecircuits. Tin/lead and
Precise solder shapes can be used
as counterweights in analog
instruments.
Connector manufacturers can attach
Exactalloy™ preform sets, providing
customers with ready-to-solder
assemblies.
tin/lead/silver alloys, stampedinto horseshoe-shaped pre-forms, are used in automotiverheostats and other hybrid circuits to prevent catastrophicfailures from excess heat.
Plumbing
Lead-free Exactalloy™ preformrings and washers are used tosolder internal plumbing joints,and to automate the joining of brass, copper, bronze andtin plate materials. CooksonElectronics has several IAPMOcertified alloys for use in theseapplications. Washers up to 2" in diameter are available.Larger rings can also be pro-duced flux-coated, flux-filledor plain.
C O O K S O N E L E C T R O N I C S
Total Quality Management is the driving force in thedesign and manufacture ofCookson Electronics precisionExactalloy™ preforms. CooksonElectronics has earned ISO9001 certification for itsExactalloy™ production facili-ties. Comprehensive qualitycontrols include SPC (statisti-cal process control), non-destructive tests and randomsample analysis.
All incoming metals are exam-ined by spectrographic analysisand all alloy materials are analyzed for content and purityprior to in-house molten stateprocessing. Cookson Electronicsunique post-alloying batchanalysis is used to identifypreforms by date, time, andmaterials used in manufactur-ing. All materials, includingfluxes, are examined usingemission spectrography, X-raydefraction, gas chromatography,atomic absorption and classicalwet chemistry techniques.
The physical characteristics ofprecision preforms, includingdimensions, weight and uni-formity, are checked meticu-lously to ensure conformancewith customer specificationsand Cookson Electronics’ rigidin-house standards.
Our ISO 9001
certifiedquality program,along withextensivetool makingcapabilitieshave madeCooksonElectronicsthe firstchoice ofsolder preformusers.
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Standard Dimensional Tolerances
DIMENSION TOLERANCE
Diameter ±0.002” (±0.051mm)
Length and Width ±0.005” (±0.127mm)
ThicknessUp to 0.005” (0.127mm) ±0.0005 in (±0.0127mm) 0.006 to 0.010” (0.152 to 0.254mm) ±10% of thicknessGreater than 0.010” (0.254mm) ±15% of thickness
Thickness (flux-filled)Up to 0.010” (0.254mm) ±0.0015” (0.0381mm) 0.011 to 0.030” (0.279 to 0.762mm) ±15% of thicknessGreater than 0.030” (0.762mm) ±10% of thickness but
not less than 0.0045” (0.1143mm)
Horizontal Burr 0.005” (0.127mm) maximum
Vertical BurrUp to 0.010” (0.254mm) 0.003” (0.0762mm) maximumGreater than 0.010” (0.254mm) 3% but not to exceed
0.005” (0.127mm)
Tin/Lead Phase Diagram
RECOMMENDED ALLOY TEMPERATURE DURING WETTING
Soft Solder AlloysALLOY MELTING TEMPERATURE RANGE
°F °C
TIN/LEAD
63Sn/37Pb 361 183
60Sn/40Pb 361-379 183-190
50Sn/50Pb 361-421 183-216
40Sn/60Pb 361-460 183-238
10Sn/90Pb 514-576 268-299
5Sn/95Pb 581-594 305-312
SILVER BEARING
62Sn/36Pb/2Ag 355 179
96.5Sn/3.5Ag 430 221
95Sn/5Ag 430-473 221-245
10Sn/88Pb/2Ag 514-517 268-299
5Sn/92.5Pb/2.5Ag 549-565 287-296
92.5Pb/2.5Ag/5 In 572 300
97.5Pb/2.5Ag 579 304
1Sn/97.5Pb/1.5Ag 588 309
SAC 305
96.5Sn/3Ag/.5Cu 422 217
TIN/ANTIMONY
100Sn 450 232
95Sn/5Sb 450-464 232-240
99Sn/1Sb 453 234
LOW-TEMPERATURE
16Sn/32Pb/52Bi 204 96
48Sn/52In 244 118
50Sn/40Pb/10Bi 248-332 120-167
43Sn/43Pb/14Bi 291-32 144-163
37.5Sn/37.5Pb/25In 274-358 134-181
50Sn/32Pb/18Cd 293 145
3Ag/97In 295 146
15Pb/5Ag/80In 298-300 148-149
GOLD BEARING
20Sn/80Au 536 280
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C O O K S O N E L E C T R O N I C S
Use these drawingsto help specifyExactalloy™ solderpreforms
The size ranges indicated on these drawings representthe dimensions in whichExactalloy™ solder preformsare available. For informationon preforms outside of thesedimensions to meet yourspecific application needs,please contact your CooksonElectronics Sales Representativeat 1-800-289-3797. You may also fax drawings to us at: 1-814-944-8094, or contact us on our web site at:www.alphametals.com
Cookson ElectronicsAssembly Materialsis a member ofCookson Electronics.The power behindthe process.
As a member of CooksonElectronics, Cookson ElectronicsAssembly Materials sharesCookson’s goal: To create totalprocess solutions that willpower our customers to greaterproductivity. We are committedto optimizing every element of our customers’ productioncapabilities by providingadvanced process development,comprehensive consulting and world-class training. Ourpeople aim to deliver realresults. To share their know-ledge in ways that improveperformance and productivity,and help our customers achievetheir goals. Cookson Electronics.The Power Behind The Process.
ODMin = .020” (0.508mm)Max = 3.00” (76.2mm)
IDMin = .008” (0.203mm)Max = OD – .010” (0.254mm)
T (Thickness)Min = .002” (0.0508mm)Max = .110” (2.794mm)
S (Side)Min = .020” (0.508mm)Max = 2.30” (58.42mm)
T (Thickness)Min = .002” (0.0508mm)Max = .200” (5.08mm)
D (Diameter)Min = .020” (0.508mm)Max = 2.10” (53.34mm)
T (Thickness)Min = .001” (0.0254mm)Max = .200” (5.08mm)
ODMin = .057” (1.4478mm)Max = 1.05” (26.67mm)
IDMin = .049” (1.2446mm)Max = 1.024” (26.01mm)
H (Height)Min = .024” (0.61mm)Max = .472” (11.99mm)
Cookson Electronics Assembly MaterialsEnergiestraat 211411 AR NaardenTelephone +31 35 695-5411Fax +31 35 694-8451www.alphametals.com
©2002 Cookson Electronics Assembly Materials
Cookson Electronics Assembly Materials4100 Sixth AvenueAltoona, PA 16602 USAOrder Hotline 800-289-3797 ext. 1685Technical Services Hotline 814-941-1690www.alphametals.com
The Power Behind The Process