Home Business ADVANCED Material Division Fine Materials For Assembly

ADVANCED Material Division

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Home Business ADVANCED Material Div Fine Materials For Assembly

Fine Materials
For Assembly

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.

Solder material with
solution for soft error

Low Alpha-ray bumping solder

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.

Bumping method and their characterization

Solder Bump proess Low-alpha solder products Characterization Availability
Pb-Sn Lead free
Ball LA/ULA/SULA Solder Ball good accuracy,high yields ok ok
Plate A/ULA/SULA Liquid
(Plating Solution)
It is possible to make a lot
of bumps for fine pitch at
the same time.
ok ok
Paste LA/ULA/SULA Paste It is suitable to make
large size bumps.
ok ok
Vapor evaporation LA/ULA Pb, Sn LA/ULA Solder Proven process, high yields ok ok
LA Grade ULA Grade SULA Grade
Pb-Sn ≤ 1.0cph/㎠
≤ 0.3cph/㎠
≤ 0.02cph/㎠
Lead free ≤ 0.01cph/㎠
≤ 0.005cph/㎠

Low alpha plating solution


  • Flat bump surface
  • Uniform bump height and Sn composition
  • High speed plating
  • Long life
  • Applicable to lead free

Alpha Grade

Parameter Pb/Sn : 95/05 Pb/Sn : 37/67 SULA Sn/Ag
Total metal content 60 g/L min 30 g/L min 50 g/L min
Cathode current density 2 - 6 A/dm2 2 - 6 A/dm2 2 - 5 A/dm2
Bath temperature 20℃ 20℃> 25℃
Flow rate(Flow Rate) 5 - 20 L 5 - 20 L 5 - 20 L
Anode type Soluble/Unsoluble Soluble/Unsoluble Unsoluble

Photograph of bumps(Before reflow)

  • Eutectic solder bump m3069-574A1Pb/Sn=37/63

  • High lead solder bump M06005-571D0 Pb/Sn=95/05

Low alpha solder ball


Alloy Composition
Pb-Sn Pb-63%Sn, Pb-5%Sn
Lead free Sn-3.5%Ag, Sn-1%Ag-0.5%Cu

Diameter and tolerance of solder ball

Diameter Tolerance
0.10, 0.15 +/- 0.005
0.20, 0.25, 0.30 +/- 0.01
0.40, 0.50 +/- 0.02

(Unit : mm)

Low alpha solder paste

We can produce several systems, compositions and powder distributions for our customer’s needs


Alloy Composition
Pb-Sn Pb-63%Sn, Pb-5%Sn
Tin-Silver Sn-3.5%Ag, Sn-3%Ag-0.5%Cu

Powder Diameter

Classification General Compsition
5 - 40㎛ 10 - 32㎛ / 5 - 15㎛ / 15 - 25㎛


A) Flux type
Activaterd Flux Flux contet chlorine
Flux type R / RMA / RA 5 - 15% Cl<0.02 / 0.02>Cl>0.1 / 0.1>Cl>0.5
B) Time variation of alpha emission

An example
Time variation of alpha emission of ULA Pb-63%Sn solder paste after reflow.

Super Ultra low alpha solder (SULA grade)

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.

Time variation of alpha emission of SULA Sn-3.5%Ag solder paste after reflow


  • Solder which correspond to alpha level < 0.002cph/cm2
  • Solder which has no time variation of alpha emission. (Zero alpha emission solder)


  • SULA Liquid (Sn-Ag)
  • SULA Solder paste (Sn-Ag, Sn-Ag-Cu)
  • SULA Solder ball (Sn-Ag , Sn-Ag-Cu)