めっき技術

Bumps

Bumps are protrusion electrodes.
Bumps convenient for electrical connections are formed on aluminum electrodes of semiconductor chips used for TAB and flip chip bonding.
Type Features & uses
Bump formation by electroplating - Costly with large-scale facilities
- Complex process
- Types of bump metals: Gold plating, solder plating, etc.
- For narrow pitches: Straight wall bumps are best suited.
- Suitable for microbumps.
- Uniformity of thickness of bump films is dependent on current distribution.
Bump formation by electroless plating - Low facility cost
- Simple process
- Types of bump metals: Limited to nickel-gold plating
- Unsuitable for narrow pitches (possible with resist mask)
- Unsuitable for microbumps (possible with resist mask)
- Uniformity of thickness of bump films is good.

(From “Denshi Buhin no Mekki Gijutsu” by Hidehiko Enomoto, Tsuneshi Nakamura; Nikkan Kogyo Shimbun Ltd.)

採用事例
Bumps
Gold bumps by electroplating
(From “Denshi Buhin no Mekki Gijutsu” by Hidehiko Enomoto,
et al.; Nikkan Kogyo Shimbun Ltd.)