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We have developed low alpha particle solder used for bumping in Flip-Chip IC(BGA,etc).
Their alpha particles are successfully reduced to 1/100-1/1000 of generic solder by utilizing our long experienced refining and atomic power technology.
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Low Alpha-ray bumping solder
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Mitsubishi Materials developed a low alpha-ray solder in which the counts of alpha-ray particles was successfully reduced to 1/100 _ 1/1000 compared to ordinary solders by utilizing our long experienced in refining and atomic power technology.
These materials are used for bumping solder in flip-chip IC, e.g. CSP,BGA and so on.
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Bumping method and their characterization
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Solder Bump
proess |
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Low-alpha
solder products |
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Characterization |
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Availability |
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| Pb-Sn |
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Lead free |
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Ball |
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LA/ULA/SULA
Solder Ball |
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good accuracy,high yields |
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ok |
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ok |
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Plate |
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LA/ULA/SULA
Liquid
(Plating Solution) |
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It is possible to make a lot of bumps for fine pitch at the same time. |
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ok |
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ok |
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Paste |
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LA/ULA/SULA
paste |
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It is suitable to make large size bumps. |
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ok |
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ok |
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Vapor
evaporation |
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LA/ULA Pb, Sn
LA/ULA Solder |
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Proven process, high yields |
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ok |
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ok |
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Alpha Grade
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LA Grade |
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ULA Grade |
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SULA Grade |
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| Spec. |
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Actual |
Spec. |
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Actual |
Spec. |
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Actual |
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Pb-Sn |
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 1.0cph/㎠ |
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0.3cph/㎠ |
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0.02cph/㎠ |
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0.01cph/㎠ |
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******* |
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******* |
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Lead free |
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******* |
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******* |
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0.01cph/㎠ |
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0.005cph/㎠ |
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0.005cph/㎠ |
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0.001cph/㎠ |
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Characterization
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Flat bump surface
Uniform bump height and Sn composition
High speed plating
Long life
Applicable to lead free
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Alpha Grade
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Parameter |
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Pb/Sn : 95/05 |
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Pb/Sn : 37/67 |
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SULA Sn/Ag |
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Total metal content |
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60 g/L min |
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30 g/L min |
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50 g/L min |
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Cathode current density |
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2 - 6 A/dm2 |
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2 - 6 A/dm2 |
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2 - 5 A/dm2 |
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Bath temperature |
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20℃ |
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20℃ |
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25℃ |
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Flow rate |
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5 - 20 L |
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5 - 20 L |
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5 - 20 L |
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Anode type |
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Soluble/unsoluble |
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Soluble/unsoluble |
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Unsoluble |
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Photograph of bumps (Before reflow)
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Composition
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Alloy |
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Composition |
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Pb-Sn |
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Pb-5%Sn, Pb-63%Sn |
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Lead free |
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Sn-3.5%Ag, Sn-1%Ag-0.5%Cu |
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Diameter and tolerance of solder ball
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(Unit : mm ) |
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Diameter |
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Tolerance |
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0.10, 0.15 |
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+/- 0.005 |
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0.20, 0.25, 0.30 |
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+/- 0.01 |
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0.40, 0.50 |
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+/- 0.02 |
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We can produce several systems, compositions and powder distributions for our customer's needs
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Composition
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Alloy |
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Composition |
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Pb-Sn |
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Pb-63%Sn, Pb-5%Sn |
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Tin-Silver |
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Sn-3.5%Ag, Sn-3%Ag-0.5%Cu |
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Powder Diameter
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Classification |
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General Compsition |
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5 - 40㎛ |
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10 - 32㎛
5 - 15㎛
15 - 25㎛
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Characterization
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a) Flux type
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Activaterd Flux |
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Flux content |
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chlorine |
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Flux type |
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R
RMA
RA |
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5 - 15% |
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Cl<0.02
0.02<Cl<0.1
0.1<Cl<0.5 |
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b) Time variation of alpha emission
An example
Time variation of alpha emission of ULA Pb-63%Sn solder paste after reflow.
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Regarding Sn-base solder, as we know, alpha particles are generated from radio isotopes, like Pb (lead) However it is easily misunderstand that Sn-base (Pb free) solder does not show any alpha emission problem, since it does not include lead.
So we developed super ultra low alpha solder for customer needs whose alpha level is very low.
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Time variation of alpha emission of SULA Sn-3.5%Ag solder paste after reflow
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Characterization
Solder which correspond to alpha level
< 0.002cph/cm2
Solder which has no time variation of
alpha emission.
(Zero alpha emission solder)
Products
SULA Liquid (Sn-Ag)
SULA Solder paste (Sn-Ag, Sn-Ag-Cu)
SULA Solder ball (Sn-Ag , Sn-Ag-Cu)
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01
Fine Materials For Assembly
02
