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Approach to Quality
Lead-Free technology report
Four technologies for making lead-free terminals work
Rohm uses four plating technologies to make lead-free terminals.
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<Solder ball formation technology>
Product application: ICs (FBGA, WCSP) Selected solder ball materials: Tin-silver-copper solder material; Sn-3.0%Ag-0.5%Cu Test result: SnAgCu solder ball material has equivalent mountability, wetting characteristics and joining reliability when compared with conventional solder ball materials. This material contains the typical lead-free solder joining material and composition used in manufacturing.
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<Electro plating technology>
Product application: ICs, photo-link modules, semiconductor lasers, parts of LEDs, sensors, transistors and diodes. Selected solder materials: Sn-2%Cu, Sn Test result: Sn-Cu plating and Sn plating has an advantage over conventional technology for its joint reliability while possessing the same level of mountability and wetting characteristics. It also has a relative cost advantage.
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<Solder dipping technology>
Product applications: Discrete semiconductor devices, LEDs, LED displays, sensors and tantalum capacitors. Selected solder materials: Tin-silver-copper; Sn-3.0%Ag-0.5%Cu Test result: SnAgCu solder dripping material has equivalent mountability, wetting characteristics and joining reliability in comparison to conventional solder dripping materials. This material is compatible with the typical lead-free solder joining material used in manufacturing because they contain the same composition.
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<Barrel plating technology>
Product applications: Chip resistors and laminated ceramic capacitors. Selected solder material: Tin; Sn Test result: Sn plating has an advantage in the reliability and stability of the plating, while possessing the same level of mountability, joining reliability and wetting and whisker generating characteristics when compared with the Sn-Pb based plating material.
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Anti-Whisker generating characteristics of lead-free external plating
Two types of lead-free plating materials were chosen-Sn-2Cu, Sn and Sn-3Ag-0.5Cu for external plating and Sn for the terminal plating of chip-type passive devices. |
Semiconductor terminal and external plating specifications
| Products group |
Frame materials |
External plating |
Plating method |
| ICs |
Cu alloy |
Sn-2Cu, Sn |
Electro plating |
| Fe Ni alloy |
Sn-2Cu, Sn |
Electro plating |
| Discrete semiconductor devices |
Cu alloy |
Sn-2Cu, Sn |
Electro plating |
| Fe Ni alloy |
Sn-2Cu, Sn |
Electro plating |
| Cu alloy |
Sn-3Ag-0.5Cu |
Hot-dipping plating |
| Fe Ni alloy |
Sn-3Ag-0.5Cu |
Hot-dipping plating |
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<Test results>
Generation of whiskers was observed with the Sn-2Cu plated and Sn plated on a semiconductor Cu alloy frame when the plated samples were kept under constant temperature and humidity at room temperature or at 30º with 70% relative humidity. The whiskers can be eliminated by thermally treating the sample at 150 º for 20 minutes.
Generation of nodule like whiskers was observed with the Sn-2Cu plated and Sn plated on a semiconductor Fe-Ni alloy frame when the sample underwent a temperature cycle test. The lengths of the whiskers are, however, less then 35 µm, and growth of the whiskers was not observed.
Generation of nodule like whiskers was also observed with Sn plating for resistors and capacitors when the sample underwent the same temperature cycle test for Sn-2Cu plated and Sn plated on a semiconductor Fe-Ni alloy frame. The whiskers, however, are less than 20 µm and growth of the whiskers was not observed.
Sn-3Ag-0.5Cu plated terminals showed no generation of whiskers in any anti-whisker generation test such as a temperature cycle test, a constant temperature and humidity test, or a storage test at room temperature.
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