185:(BGA) sphere and solder paste deposit, is a failure mode that has seen increased frequency since the transition to lead-free soldering. Often missed during inspection, a head-in-pillow (HIP) defect appears like a head resting on a pillow with a visible separation in the solder joint at the interface of the BGA sphere and reflowed paste deposit. An electronics manufacturer needs experience with the printing process, specifically the paste characteristics, to avoid costly re-work on the assemblies. The paste's physical characteristics, like viscosity and flux levels, need to be monitored periodically by performing in-house tests.
605:
40:
202:
20:
568:
The characteristic of a material's tendency to spread after application. Theoretically, the paste's sidewalls are perfectly straight after the paste is deposited on the circuit board, and it will remain like that until the part placement. If the paste has a high slump value, it might deviate from the
554:
is a measure of the viscosity of the solder paste at rest, compared to the viscosity of "worked" paste. Depending upon the formulation of the paste, it may be very important to stir the paste before use, to ensure that the viscosity is appropriate for proper application. When solder paste is moved by
235:
The size and shape of the metal particles in the solder paste determines how well the paste will "print". A solder ball is spherical in shape; this helps in reducing surface oxidation and ensures good joint formation with the adjoining particles. Irregular particle sizes are not used, as they tend to
176:
A majority of the defects in circuit-board assembly are caused due to issues in the solder-paste printing process or due to defects in the solder paste. There are many different types of defects possible, e.g. too much solder, or the solder melts and connects too many wires (bridging), resulting in a
658:
For a good soldered joint, the proper amount of solder paste must be used. Too much paste may result in a short circuit; too little may result in poor electrical connection or physical strength. Although solder paste typically contains around 90% metal in solids by weight, the volume of the soldered
650:
The paste manufacturer will suggest a suitable reflow temperature profile to suit their individual paste. The main requirement is a gentle rise in temperature to prevent explosive expansion (which can cause "solder balling"), yet activate the flux. Thereafter, the solder melts. The time in this area
585:
Tack is the property of a solder paste to hold a component after the component had been placed by the placement machine. Hence, tack life is the critical property of solder pastes. It is defined as the length of time that solder paste can remain exposed to the atmosphere without a significant change
188:
When making PCBs (printed circuit boards), manufacturers often test the solder paste deposits using SPI (solder paste inspection). SPI systems measure the volume of the solder pads before the components are applied and the solder melted. SPI systems can reduce the incidence of solder-related defects
698:
This procedure is quite thorough, yet minimizes the amount of testing required to differentiate between excellent and poor solder pastes. If multiple solder pastes are evaluated, the procedure can be used to eliminate the poor pastes from their poor printing quality. Further testing, such as solder
594:
Response-to-pause (RTP) is measured by the difference in volume of solder paste deposition as a function of number of prints and pause time. A large variation in the print volume after a pause is unacceptable as this causes end of line defects such as shorts or opens. A good solder paste shows less
559:
on the stencil, the physical stress applied to the paste causes the viscosity to drop, allowing the paste to flow easily through the apertures on the stencil. When the stress on the paste is removed, it regains its viscosity, preventing it from flowing on the circuit
513:
flux is designed to leave only small amounts of inert flux residues. No-clean pastes save not only cleaning costs, but also capital expenditures and floor space. However, these pastes need a very clean assembly environment and may need an inert reflow environment.
193:(Switzerland), Sinic-Tek (China), Koh Young (Korea), GOEPEL electronic (Germany), CyberOptics (US), Parmi (Korea) and Test Research, Inc. (Taiwan). Offline systems are manufactured by various companies such as by VisionMaster, Inc. (US) and Sinic-Tek (China).
151:
components by printing solder paste in and over the holes. The sticky paste temporarily holds components in place; the board is then heated, melting the paste and forming a mechanical bond as well as an electrical connection. The paste is applied to the board by
659:
joint is only about half that of the solder paste applied. This is due to the presence of flux and other non-metallic agents in the paste, and the lower density of the metal particles when suspended in the paste as compared to the final, solid alloy.
533:
The degree to which the material resists the tendency to flow. The viscosity for a particular paste is available from the manufacturer's catalog; in-house testing is sometimes needed to judge the remaining usability of solder paste after a period of
639:
As well as forming the solder joint itself, the paste carrier/flux must have sufficient tackiness to hold the components while the assembly passes through the various manufacturing processes, perhaps moved around the factory.
569:
expected behavior, as now the paste's sidewalls are not perfectly straight. A paste's slump should be minimized, as slump creates the risk of forming solder bridges between two adjacent lands, creating a short circuit.
217:
paste. The tackiness of the flux holds components in place until the soldering reflow process melts the solder. As a result of environmental legislation, most solders today, including solder pastes, are made of
1039:
1010:
975:
662:
As with all fluxes used in electronics, residues left behind may be harmful to the circuit, and standards (e.g., J-std, JIS, IPC) exist to measure the safety of the residues left behind.
236:
clog the stencil, causing printing defects. To produce a quality solder joint, it's very important for the spheres of metal to be very regular in size and have a low level of oxidation.
632:, by pin transfer (where a grid of pins is dipped in solder paste and then applied to the board), or by jet printing (where the paste is ejected onto the pads through nozzles, like an
839:
677:
Solder paste must be refrigerated when transported and stored in an airtight container at a temperature between 0-10 °C. It should be warmed to room temperature for use.
864:
695:
The main reason why evaluation of solder paste is necessary, is because 50-90% of all defects result from printing problems. Hence, paste evaluation is critical.
771:
239:
Solder pastes are classified based on the particle size by IPC standard J-STD 005. The table below shows the classification type of a paste compared with the
1054:
1000:
964:
925:
482:
According to IPC standard J-STD-004 "Requirements for
Soldering Fluxes", solder pastes are classified into three types based on the flux types:
798:
595:
variation in the volume of the prints after pause. However, another may show large variations and also an overall decreasing trend in volume.
577:
The amount of time solder paste can stay on a stencil without affecting its printing properties. The paste manufacturer provides this value.
1073:
586:
in tack properties. A solder paste with long tack life is more likely to provide the user with a consistent and robust printing process.
824:
887:
1001:"First-Ever Temperature Stable Solder Paste Unveiled - Major Development in Solder Paste Formulation Set to Change Market Paradigms"
243:
and particle size. Some suppliers use proprietary particle size descriptions, Henkel/Loctite descriptions are given for comparison.
123:
680:
Recently, new solder pastes have been introduced that remain stable at 26.5 °C for one year and at 40 °C for one month.
911:
868:
61:
104:
57:
76:
971:
699:
reflow performance, solder joint quality, and reliability testing can then be performed on the solder paste finalists.
506:
fluxes are made up of organic materials and glycol bases. There is a wide variety of cleaning agents for these fluxes.
83:
50:
492:, a natural extract from pine trees. These fluxes can be cleaned if required after the soldering process using a
90:
165:
140:
72:
625:
178:
895:
802:
189:
to statistically insignificant amounts. Inline systems are manufactured by various companies such as
777:
746:
1100:
1005:
497:
1067:"White Paper on SMT Under Stencil Wiper Rolls - An insight into the main products on the market"
604:
1066:
872:
741:
214:
28:
766:
644:
613:
157:
522:
In using solder paste for circuit assemblies, one needs to test and understand the various
899:
799:"Reducing Head in Pillow Defects - Head in pillow defects: causes and potential solutions"
617:
182:
97:
946:
761:
633:
1094:
666:
144:
153:
148:
683:
Exposure of the solder particles, in their raw powder form, to air causes them to
669:, water-soluble pastes (which have compulsory cleaning requirements) are common.
543:
39:
629:
825:"Marktübersicht SPI-Systeme - Den optimalen Lotpasten-Druckprozess im Visier"
756:
621:
547:
523:
252:
240:
177:
short circuit. Insufficient amounts of paste result in incomplete circuits.
147:
components to pads on the board. It is also possible to solder through-hole
721:
These three concerns helped to spawn three enclosed systems for printing.
201:
19:
1050:
556:
665:
In most countries, "no-clean" solder pastes are the most common; in the
684:
493:
161:
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process by a solder paste printer, in which paste is deposited over a
550:
changes with applied shear force (such as stirring or spreading). The
932:
751:
219:
210:
655:. A reasonably rapid cool-down period is required after this time.
603:
489:
200:
965:"Solder Volumes for Through-Hole Reflow-Compatible Connectors"
33:
190:
16:
Material used in the manufacture of printed circuit boards
892:
Online postgraduate courses for the electronics industry
711:
It can dry out on the stencil if kept out for too long.
920:
918:
245:
64:. Unsourced material may be challenged and removed.
717:It is expensive and waste has to be minimized.
1072:. 1.0. Swiftmode Malaysia (Penang) Sdn. Bhd.
1038:Ashley, Dan; Adamson, Steven J. (July 2008).
865:"J-STD-005 Requirements for Soldering Pastes"
772:Restriction of Hazardous Substances Directive
8:
164:; then the components are put in place by a
27:Solder paste sometimes refers to soldering
707:The main concerns about solder paste are:
124:Learn how and when to remove this message
863:Solder Paste Task Group (January 1995).
624:mask to create the desired pattern on a
18:
789:
209:A solder paste is essentially powdered
205:Solder paste viewed under a microscope.
926:"Technical Data Sheet LOCTITE HF 212"
7:
612:Solder paste is typically used in a
62:adding citations to reliable sources
1009:. The Electronics Group of Henkel.
687:, so exposure should be minimized.
643:Printing is followed by a complete
1040:"Advanced solder paste dispensing"
14:
1065:O'Brien, Dennis H. (2013-03-19).
38:
1079:from the original on 2014-11-07
1016:from the original on 2016-03-02
981:from the original on 2018-06-18
845:from the original on 2018-06-18
500:) or saponifying flux remover.
181:, or incomplete coalescence of
49:needs additional citations for
869:Electronic Industries Alliance
823:Robles Consée, Marisa (2015).
628:. The paste may be dispensed
526:properties of a solder paste.
139:is used in the manufacture of
1:
608:Solder paste printed on a PCB
31:that does not contain solder.
972:Tyco Electronics Corporation
999:Wilding, Ian (2016-02-08).
886:Tarr, Martin (2006-10-03).
265:(less than 1% larger than)
1117:
518:Properties of solder paste
282:Henkel Powder Description
247:
26:
1047:Surface Mount Technology
728:MPM Rheometric Pump Head
867:. Arlington, Virginia:
838:(7): 42–45. 450pr0715.
496:(potentially including
947:"Solder-Paste Printer"
609:
206:
179:Head-in-pillow defects
166:pick-and-place machine
141:printed circuit boards
24:
951:Yamaha Motor Co., Ltd
888:"Solder paste basics"
797:Alpha (2010-03-15) .
626:printed circuit board
607:
488:fluxes are made with
279:(10% max. less than)
204:
22:
896:University of Bolton
58:improve this article
801:. 3. Archived from
778:Non-Newtonian fluid
747:Helping hand (tool)
653:Time Above Liquidus
546:, meaning that its
498:chlorofluorocarbons
270:(80% min. between)
268:Particle size in μm
1006:Henkel Electronics
610:
255:in lines-per-inch
249:Type designation
207:
25:
591:Response-to-pause
552:thixotropic index
539:Thixotropic index
475:
474:
260:(no larger than)
134:
133:
126:
108:
1108:
1087:
1085:
1084:
1078:
1071:
1061:
1059:
1053:. Archived from
1044:
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1021:
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969:
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898:. Archived from
883:
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860:
854:
853:
851:
850:
844:
829:
820:
814:
813:
811:
810:
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767:Reflow soldering
714:It may be toxic.
645:reflow soldering
614:stencil-printing
542:Solder paste is
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158:stencil printing
129:
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42:
34:
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1032:Further reading
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827:
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796:
795:
791:
786:
738:
731:Fuji Cross Flow
705:
693:
675:
618:stainless steel
602:
520:
480:
278:
277:Min. size in μm
274:
273:Avg. size in μm
269:
264:
263:Max. size in μm
259:
258:Max. size in μm
233:
228:
199:
183:ball grid array
174:
130:
119:
113:
110:
67:
65:
55:
43:
32:
17:
12:
11:
5:
1114:
1112:
1104:
1103:
1093:
1092:
1089:
1088:
1062:
1060:on 2012-08-12.
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956:
938:
914:
878:
855:
815:
788:
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762:Wave soldering
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634:inkjet printer
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226:Classification
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73:"Solder paste"
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15:
13:
10:
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902:on 2010-11-12
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859:
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841:
837:
834:(in German).
833:
826:
819:
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805:on 2013-12-03
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672:
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667:United States
663:
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631:
630:pneumatically
627:
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545:
541:
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512:
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504:Water-soluble
501:
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213:suspended in
212:
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145:surface mount
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78:
75: –
74:
70:
69:Find sources:
63:
59:
53:
52:
47:This article
45:
41:
36:
35:
30:
21:
1081:. Retrieved
1055:the original
1046:
1018:. Retrieved
1004:
994:
983:. Retrieved
959:
950:
941:
935:. June 2016.
904:. Retrieved
900:the original
891:
881:
858:
847:. Retrieved
835:
832:Productronic
831:
818:
807:. Retrieved
803:the original
792:
720:
706:
697:
694:
682:
679:
676:
664:
661:
657:
652:
651:is known as
649:
642:
638:
611:
574:Working life
551:
521:
510:
508:
503:
502:
485:
484:
481:
238:
234:
208:
187:
175:
168:or by hand.
154:jet printing
149:pin in paste
137:Solder paste
136:
135:
120:
111:
101:
94:
87:
80:
68:
56:Please help
51:verification
48:
23:Solder Paste
725:DEK ProFlow
544:thixotropic
524:rheological
486:Rosin based
197:Composition
143:to connect
1083:2018-06-18
1020:2021-02-25
985:2016-08-29
906:2010-10-03
871:(EIA) and
849:2018-06-18
809:2018-06-18
784:References
691:Evaluation
386:-500/+635
361:-400/+635
336:-325/+500
312:-200/+325
114:March 2017
84:newspapers
1101:Soldering
757:Soldering
647:process.
622:polyester
548:viscosity
530:Viscosity
253:Mesh size
241:mesh size
220:lead-free
191:Delvitech
1095:Category
1074:Archived
1051:PennWell
1011:Archived
976:Archived
840:Archived
736:See also
703:Concerns
557:squeegee
511:no-clean
222:alloys.
685:oxidize
673:Storage
494:solvent
478:By flux
454:Type 8
432:Type 7
408:Type 6
383:Type 5
358:Type 4
333:Type 3
309:Type 2
297:150-75
287:Type 1
231:By size
162:syringe
98:scholar
933:Henkel
894:. UK:
774:(RoHS)
752:Solder
560:board.
395:25–10
369:38–20
344:45–25
320:75–45
211:solder
100:
93:
86:
79:
71:
1077:(PDF)
1070:(PDF)
1058:(PDF)
1043:(PDF)
1014:(PDF)
979:(PDF)
968:(PDF)
929:(PDF)
843:(PDF)
828:(PDF)
565:Slump
490:rosin
443:11–2
420:15–5
411:-635
105:JSTOR
91:books
836:2015
742:Flux
582:Tack
555:the
534:use.
465:8–2
403:KBP
378:DAP
353:AGS
294:150
215:flux
77:news
29:flux
873:IPC
636:).
620:or
600:Use
462:10
459:11
440:11
437:15
417:15
414:20
400:10
392:25
389:30
375:20
372:31
366:38
350:20
347:36
341:45
326:20
323:60
317:75
302:20
172:Use
160:or
60:by
1097::
1049:.
1045:.
1003:.
974:.
970:.
949:.
931:.
917:^
890:.
830:.
509:A
425:5
156:,
1086:.
1023:.
988:.
953:.
909:.
875:.
852:.
812:.
127:)
121:(
116:)
112:(
102:·
95:·
88:·
81:·
54:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
