Solderability PowerPAKr SO-8 PowerPAK 1212-8 When Using Different Sold
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AN825
Solderability PowerPAKr SO-8 PowerPAK 1212-8 When Using Different Solder Pastes Profiles
Jess Brown Kandarp Pandya
INTRODUCTION
Next-generation PowerPAK packages from Vishay Siliconix feature very thermal resistances, enabling higher power dissipation with added benefit reduced board space increased available area. With MOSFET packaging technology, concerns about manufacturability will arise, particular with respect yield figures, failure rates, solderability, short circuits caused solder bridging, drifting part during mounting process. These concerns often relate solder profile, layout, size package. However, case PowerPAK, three major concerns shift position part during manufacturing, possibility solder bridging across small pads large pads, possibility solder voids. certain extent, first issues resolved through visual inspection. presence voids, however, cannot determined visually nature package. result, possible presence solder voids greatest concern manufacturers using product. this application note alleviate concerns about these packages illustrating through practical experimentation solder joint quality voiding several solder pastes when used with PowerPAK SO-8 PowerPAK 1212-8 packages.
PACKAGE TYPES
Four types packages were chosen investigation: PowerPAK SO-8 single, PowerPAK SO-8 dual, PowerPAK 1212-8 single PowerPAK 1212-8 dual. recommended landing patterns were used described Application Note AN826, Recommended Minimum Patterns With Outline Drawing Access Vishay Siliconix MOSFETs, separate boards, with HASL surface finish, were built PowerPAK SO-8 PowerPAK 1212-8, with each board consisting single devices five dual devices shown Figure Examples devices used solderability study also shown Figure
PowerPAK SO-8 Single
PowerPAK SO-8 Single
PowerPAK SO-8 Dual
PowerPAK 1212 Single
PowerPAK 1212 Single
PowerPAK 1212 Dual
PowerPAK SO-8 Dual
Size: 6.1x 5.1mm Pitch: 1.27mm Plating:SnPb SO-8 Packages
PowerPAK 1212 Dual
Size: 3.3x 3.3mm Pitch: 0.65mm Plating: SnPb 1212-8 Packages
SO-8
1212-8
FIGURE PowerPAK PCBs Packages Used Investigations
Document Number: 72116 15-Dec-03
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AN825
Horizon Printer
Siemens Machine
Heller 1800EXL Oven
Optek X-Ray Inspection System
FIGURE Equipment Used Solder Tests
PLACEMENT, SOLDERING, HEATING INSPECTION EQUIPMENT
pick-and-place machine used Siemens (Figure configured with six-nozzle collect-and-place head with vision module. placement pressure (204 grams) with placement accuracy microns, components were picked from tape-and-reel. stencil printing achieved with Horizon printer (Figure 4-mil thickness, laser-cut print pressure front rear, print speed mm/s front rear. oven reflow Heller 1800EXL oven with nine heating cooling zones. solder void inspections were achieved using Optek X-ray machine.
Details Solder Pastes Used Investigations Cat.#
UP78 Omnix 5000 NC-SMQ92J TLF-206-19 NC73 RP15 WS22 CR39 CR36 MP200
TABLE
Type
Clean Clean Clean Lead Free Clean Clean Water Soluble Lead Free Clean Clean
Manufacturer
Ultraprint Alpha-Fry Corp. Indium Corp. Tamura, Japan Loctite (Multicore) Loctite (Multicore) Loctite (Multicore) Loctite (Multicore) Loctite (Multicore) Loctite (Multicore)
Data Appendix
SOLDER PASTES
Several solder paste types, including lead-free, water-soluble, no-clean, were used. Details provided Table
SOLDER PROFILE
account these different solders, three different oven profiles were required. These found Figures Zone
entrance cool
Upper
Lower
FIGURE Oven Profile CR39 TLF-206-19 Solders
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AN825
Zone
entrance cool
Upper Lower
FIGURE Oven Profile RP15 Solder
Zone
Upper Lower
FIGURE Oven profile UP78, Omnix 5000, NC-SMQ92J, NC73, WS22
STENCILS
Examples design stencils used investigation PowerPAK SO-8 1212-8 shown Figure Figure respectively.
INVESTIGATIONS INTO PACKAGE SHIFTING POSSIBLE SOLDER BRIDGING
basic layout PowerPAK packages consists small leads with fine pitch located side device large lead other side package. This means that
Document Number: 72116 15-Dec-03
lead frame asymmetrical, resulting dissimilar metal masses, which could cause device move during mounting soldering different tensions exerted different metal masses. This because surface tension resulting from large quantity molten solder under large leads pads produce lateral shift part, possibly causing electrical short circuit. This lateral shift packages' lead frame design could cause solder bridging between small large leads device, solder pads board, also between solder pads themselves.
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AN825
FIGURE Stencil PowerPAK SO-8
FIGURE Stencil PowerPAK 1212-8
Therefore, PowerPAK devices were examined solder bridging three areas: between consecutive leads, lead-to-pad, pad-to-pad. manufacture achieved using recommended patterns, described earlier, with stencil controlling thickness openings. operating pressure squeegee pick-and-place machine selected ensure that adequate amount solder paste spread under part.
This investigation shown that PowerPAK SO-8 PowerPAK 1212-8 packages suitable assembly using industry-standard reflow procedures processes. results show that there solder bridges fine-pitch gaps between consecutive leads, even from lead-to-pad pad-to-pad. results also show electrical shorts part self-aligns pattern. achieve this result recommended patterns solder mask.
PowerPAK SO-8
Figure shows first shifting part left during placement then self-alignment part after reflow X-ray shows shift lead frame with respect pads solder paste. X-ray part after reflow shows that part self-aligned pads that there short circuits solder bridging. also shows solder spreading limited size. This confirmed Metcal 5000 visual inspection shown Figure (f).
SOLDER VOIDS
issues with PowerPAK package lack visibility solder joint between printed circuit board leads package, also lack visibility possible solder voids larger pin-pad solder joints. reason these voids could large lead pads, which have high metal mass large amount molten solder. latter entrap gases from solder paste, resulting solder voids. Therefore, ensure that PowerPAK device performs well terms solderability, investigation included several solder pastes mounting PowerPAK devices. results provided below. variety solder pastes were used determine solder paste suitability. These pastes included no-clean, water-soluble, lead-free pastes from number different manufacturers, including Ultraprint, Alpha, Indium, Tamura Loctite. Through joint expertise solder manufacturer (Loctite) contract manufacturer (Flextronics), reflow profile modified minimize voids.
Document Number: 72116 15-Dec-03
PowerPAK 1212-8
Figure shows photographs X-rays 1212-8 package during placement reflow. Figure show that part shifted during placement, X-ray shows potential solder bridging concerns. However, during reflow process, part realigns itself pads, such solder spreading again limited pads. This confirmed optical visual inspection, where between drain pads pins seen.
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AN825
Solder Paste Application
Part Placement
X-Ray Part Placement
Part Placement After Reflow
X-Ray After Reflow
Optical Visual Inspection
FIGURE Example Lateral Shift Then Self-Centering Realignment PowerPAK SO-8
Solder Paste Application
Part Placement
X-Ray Part Placement
Part Placement After Reflow
X-Ray After Reflow
Optical Visual Inspection
FIGURE Example Lateral Shift Then Self-Centering Realignment 1212-8 PowerPAK
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AN825
UP-78 SOLDER PASTE
Figures shows solder voids using UP-78 solder paste. worst-Case parts showed voids greater than 30%. improved solder profile, Figure showed improvements, voiding this solder paste still classified between 50%.
Best-Case (<20%)
Worst-Case (>30%)
Best-Case (<20%)
Worst-Case (>30%)
Single PowerPAK SO-8
Dual PowerPAK SO-8
FIGURE Solder Voids UP-78 Solder Paste Using Initial Oven Profile
Voids: <20% Single PowerPAK SO-8
Voids: <20% Dual PowerPAK SO-8
Voids: <20% Single PowerPAK 1212
Voids: <20% Dual PowerPAK 1212
FIGURE Solder Voids UP-78 Solder Paste Using Improved Oven Profile
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Document Number: 72116 15-Dec-03
AN825
OMNIX 5000 SOLDER PASTE
Omnix solder paste performed very well. solder voids shown Figures PowerPAK SO-8 1212-8 respectively. maximum voids this case were classified less than 20%.
Best-Case
Worst-Case
Best-Case
Worst-Case
Single PowerPAK SO-8 Voids:
Dual PowerPAK SO-8 Voids:
FIGURE Solder Voids Omnix 5000 Solder Paste
Best-Case
Worst-Case
Best-Case
Worst-Case
Single PowerPAK 1212-8 Voids:
Dual PowerPAK 1212-8 Voids:
FIGURE Solder Voids Omnix Solder Paste
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AN825
INDIUM SOLDER PASTE
Indium solder paste also success, with boards having voids less than 20%, shown Figures
Best-Case
Worst-Case
Best-Case
Worst-Case
Single PowerPAK SO-8 Voids:
Dual PowerPAK SO-8 Voids:
FIGURE Solder Voids Indium Solder Paste
Best-Case
Worst-Case
Best-Case
Worst-Case
Single PowerPAK 1212-8 Voids:
Dual PowerPAK 1212-8 Voids:
FIGURE Solder Voids Indium Solder Paste
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TAMURA SOLDER PASTE
Tamura solder paste perform well some other solder pastes under reflow conditions specified. such, Tamura solder paste classified having voiding, shown Figures
Best-Case
Worst-Case
Best-Case
Worst-Case
Single PowerPAK SO-8 Voids:
Dual PowerPAK SO-8 Voids:
FIGURE Solder Voids Tamura Solder Paste
Best-Case
Worst-Case
Best-Case
Worst-Case
Single PowerPAK 1212-8 Voids:
Dual PowerPAK 1212-8 Voids:
FIGURE Solder Voids Tamura Solder Paste
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AN825
NC-73 SOLDER PASTE
NC-73 solder paste perform very well, shown Figures with majority parts having greater than voiding. PowerPAK SO-8 devices were classified having greater than void, whereas PowerPAK 1212-8 devices were classified having void 50%.
Best-Case voids <20% (very few)
Worst-Case >40% (majority)
Best-Case voids <20% (very few)
Worst-Case >40% (majority)
Single PowerPAK SO-8
Dual PowerPAK SO-8
FIGURE Solder Voids NC-73 Solder Paste
Best-Case voids <20% (very few)
Worst-Case >40% (majority)
Best-Case voids <20% (very few)
Worst-Case >40% (majority) Dual PowerPAK 1212
Single PowerPAK 1212-8
FIGURE Solder Voids NC-73 Solder Paste
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AN825
RP-15 SOLDER PASTE
RP-15 solder paste resulted high percentage voiding, even with suggested voiding oven profile (Figure 20). with NC-73 solder paste, voiding
Temp (Deg
PowerPAK SO-8 classified being greater than 50%, whereas PowerPAK 1212-8 MOSFETs voiding level. Figures
Time
FIGURE Suggested Improved Voiding Oven Profile RP15
Best-Case Voids
Worst-Case
Best-Case Voids
Worst-Case
Single PowerPAK SO-8 Voids:
Dual PowerPAK SO-8 Voids:
FIGURE Solder Voids RP-15 Solder Paste
Best-Case Voids
Worst-Case
Best-Case Voids
Worst-Case
Single PowerPAK 1212-8 Voids: -50%
Dual PowerPAK 1212-8 Voids: -50%
FIGURE Solder Voids RP-15 Solder Paste
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AN825
WS-22 SOLDER PASTE
WS-22 solder paste resulted successful placement both PowerPAK SO-8 1212-8. voiding level very good classified being 20%, shown Figures
Best-Case Voids
Worst-Case
Best-Case Voids
Worst-Case
Single PowerPAK SO-8 Voids: 10-20%
Dual PowerPAK SO-8 Voids: 10-20%
FIGURE Solder Voids WS-22 Solder Paste
Best-Case Voids
Worst-Case
Best-Case Voids
Worst-Case
Single PowerPAK 1212-8 Voids:
Dual PowerPAK 1212-8 Voids:
FIGURE Solder Voids WS-22 Solder Paste
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AN825
CR-39 SOLDER PASTE
CR-39 solder paste exhibited void levels PowerPAK 1212-8 greater than (Figure 26), whereas PowerPAK SO-8 parts voiding levels (Figure 25).
Best-Case Voids
Worst-Case
Best-Case Voids
Worst-Case
Single PowerPAK SO-8 Voids:
Dual PowerPAK SO-8 voids
FIGURE Solder Voids CR-39 Solder Paste
Best-Case Voids
Worst-Case
Best-Case Voids
Worst-Case
Single PowerPAK 1212-8 Voids: >50%
Dual PowerPAK 1212-8 Voids: >50%
FIGURE Solder Voids CR-39 Solder Paste
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AN825
summary solder paste void tests given Table which shows results single dual versions PowerPAK SO-8 PowerPAK 1212-8. Four boards each package type were evaluated each variety solder paste. Each board contained five single-channel five dual-channel devices.
CONCLUSIONS
This note effectively considers issues: movement part during placement associated solder bridging, solder voids beneath mounted part. Solder Bridging Part Movement During Placement pick-and-place machine caused spreading solder paste before reflow, which turn reduced pad-to-pad gap, albeit temporarily. Before reflow process, MOSFET shift off-center result operating pressure during part placement. specifics this happens also depend tolerances pick-and-place machine. PowerPAK devices realign themselves during reflow process. solder bridges were observed during these movements realignments. Therefore, been shown that PowerPAK SO-8 PowerPAK 1212-8 packages suitable surface mounting assembly using industry standard re-flow procedure process. results show solder bridges fine gaps between consecutive leads, gaps between lead pad, between pads themselves. There were also electrical shorts mounted device part aligned itself pattern during re-flow period. ensure that there solder bridges shorts, recommended patterns must used conjunction with corresponding solder masks. recommended pattern greatly reduces pad-to-pad solder-bridging shift pull part surface tension. Solder Voids
Summary Solder Paste Voids Voids PKSO-8
10-20% 20-50% 50+%
TABLE
Voids PK1212-8
10-20% 20-50% 50+%
Solder Paste
UP78 clean)
Board
Omnix 5000 clean)
Indium clean)
Multicore NC73 clean)
Multicore WS22 clean)
investigate possibility solder voids, variety solder pastes were used mount PowerPAK SO-8 1212-8 MOSFETs. manufacturers' recommended oven profiles were used reflow process. solder pastes which generated large voids, reflow profile varied minimize solder voids. Only marginal improvements were noticed results, although solder paste manufacturers attempting produce oven reflow profile that will improve voiding some these solder pastes. contract manufacturer specified that solder void less than acceptable. also noted that adequate amount paste, means good stencil design, important fault-free soldering, appropriate selection pressure speed parameters solder paste printing machine pick-place machine also critical obtaining good results. Typically, solder profiles recommended solder manufacturers, marginal variance applied improve upon solder voids. However, excessive increase reflow temperature lead burnt (dry) solder, whereas decreasing reflow temperature lead incomplete solder joint. study showed that using correct solder paste, oven profile, solder mask, possible obtain solder joints with less than voiding.
Document Number: 72116 15-Dec-03
Loctite RP15 clean)
Loctite CR39 (Lead-free)
Tamura (Lead-free)
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