本研究以熱音波覆晶接合製程將矽晶片
直接覆晶接合於軟性基板上，但軟性基板在熱
音波覆晶接合中，超音波能量易被軟板所吸
收，無法達成良好之接合，故於軟性基板銅電
極上鍍著鎳膜，再於鎳膜上方鍍著銀層做為接
著層，期望鎳膜可使超音波能量有效傳遞至接
合介面，用以提升熱音波覆晶接合製程中矽晶
片與軟性基板銅電極之接著率與剪力強度。
選用適當熱音波接合參數，矽晶片可成功
覆晶接著於具鎳膜之軟性基板上，且在較小超
音波功率下，即能達到100%接著率，而剪力
測試結果顯示矽晶片與具鎳膜鍍層軟性基板
之剪力強度高於業界規範之要求。矽晶片與軟
板之覆晶接合強度與超音波功率成正比，但選
用過大超音波功率時，熱音波覆晶機之接合負
荷亦需隨之提升，使晶片與軟板維持穩定接
觸，超音波功率方可傳遞之接合介面；若接合
時間過長，接合介面處之超音波功率過高，金
凸塊與矽晶片接著層易產生脫層缺陷，進而降
低矽晶片與軟性基板之剪力強度。由剪力測試
後之斷面觀察得知矽晶片與具鎳膜之軟性基
板銅電極之破斷模式為金凸塊破壞，顯示金凸
塊與軟性基板上之接合強度較金凸塊強度還
高，且該強度高於業界規範之要求，顯示於軟
板銅電極上鍍著鎳膜，可有效提高矽晶片與軟
板之接著率與接著強度。本實驗所得適用於矽
晶片與軟板熱音波覆晶接合之參數為超音波
功率20.66W、接合負荷625gf、接合時間0.3s、
接合溫度200℃。
鍍著0.5μm鎳膜於軟性基板銅電極上，可
有效提高矽晶片與軟板之接著率與接合強
度，該技術應用於軟板之構裝技術深具潛力。
關鍵字： 熱音波覆晶接合製程、軟性基板、
鎳鍍膜
The purpose of this study was to investigate
that the influence of the nickel layer on the
bondability and bonding strength of silicon chips
and flex substrates they were bonded using
thermosonic flip-chip process. The flex substrate
was electroplated with a nickel layer on the
surface of copper electrodes and the silver film
was then deposited on the nickel layer. This
nickel layer was expected to improve the
bondability and bonding strength of silicon chip
flip-bonded on flex substrates. The thickness of
the silver layer and the nickel layer were
approximately 0.5μm. Thermosonic flip-chip
bonding experiments were conducted using an
automatic thermosonic flip-chip bonder
developed by ITRI. After chips bonded on the
flex substrates, a subsequent die-shear test was
performed to evaluate the bonding strength
according to with JESD22-B116 standard.
Chips were successfully thermosonic
flip-chip bonded on flex substrates with
depositing the nickel layer. 100% bondability
can be obtained and bonding strength exceeds
the minimum requirements stated in the related
specifications for chips flip-bonded on flex
substrates with 0.5μm-thick nickel layer. In
contrast to a good bonding quality of chips
flip-bonded on flex substrates with a nickel layer,
a poor bonding strength was found when chips
flip-bonded on copper electrodes without nickel
layer. The nickel layer was effective to improve
the propagation of ultrasonic power to bonding
interface between silver bonding layer and gold
bumps, and increases the bonding efficiency of
ultrasonic power during thermosonic bonding
process. The bonding strength and bondability
were thus enhanced. The adequate bonding
parameters of chips thermosonic bonding to flex
substrates were 20.66 W in ultrasonic power,
625 gf in bonding force, 0.3 s in bonding time
and 200℃ in bonding temperature.
Deposition of the 0.5μm-thick nickel layer
on the copper electrodes over flex substrates is
an effective scheme to improve the bonding
strength and bondability of chips thermosonic
flip-bonded on the flex substrates.
Keywords: Thermosonic flip-chip bonding,
Flex substrate, Nickel layer
