大綱
|
摘要
本研究成功利用氣溶膠噴射列印技術(AJP)取代傳統製程完成多層重新佈線層(Redistribution Layer, RDL)結構封装體,並證實具有高度技術上可行性。研究中透過溶劑對奈米銀顆粒墨水濃度進行調整,結果顯示比例2:1(Ag:PGME)之銀墨水濃度,具有良好的霧化性與穩定性。再者,藉由適當的鞘氣氣流與霧化氣流參數,可成功列印出品質良好之銀線路,且可依需求將線寬控制於 20-30um。而銀黑水透過直接溫度燒結法,燒結在180°C以上1小時後,即可具有良好之導電性、傳翰穩定度與附著性,其最小平均電阻率達到2.22× 10-69cm,約為塊銀之2倍,而附著性等級則達到5B。此外,亦透過添加高分子墨水強化銀黑水之附著性,具有明顯的效果,可以進一步提升銀墨水之附著性。
本研究藉由上述所獲得之銀墨水列印参數,列印單層 RDL與多層RDL結構,並透過不同層数之銀焊墊進行打線接合與推拉力測試驗證。研究結果證寳所列印之銀電路與焊墊具有可重複性,其線宽與焊墊尺寸,分別約為 25-28 um與 100 110um。而添加了高分子層的多層 RDL
結構,在僅有一層銀焊墊時,即可達到100%打線良率,並可通過推拉力測試規範的標準值。但是單層 RDL
結構的銀焊墊則需列印至三層時,才能達到相同的強度,說明打線接合良率輿金球受力強度會受到銀焊墊厚度與高分子層影響。此外,本研究中列印 800
顆含三層銀焊塾的多層 RDL結構封装體,進行放量可靠度測試(RA)。研究結果證實,RDL
封装體在正常溫濕度與高低溫環境中具有良好的可靠度,其溫度循環測試(TCT)與高溫儲存測試(TSL)的良率可達到100%。但當濕度提高至 85%RH
以上之高壓高濕的環境測試時,會加速濕氣從結構的缺陷與層與層間渗入,使得封裝體容易有分層與電性失效問題,導致較低的可靠度,高加速溫濕度測試(HAST)的良率下降至 96%,而具100%RH
之高溫水蒸汽壓力測試(或稱壓力鍋測試,PCI)良率更是下降至76%。
最後,經過綜合評估分析,雖然 AJP
技術在生產速度上仍不及傳統製程,距離箕際量產應用還有許多設備奥成本問題需要考量,但由於其具有免光罩直接結構列印丶多範圍材料選擇與少化學廢料等優點,且經本研究證明其可成功應用於 RDL
結構封裝體製造,擁有高度的技術可行性輿可靠度。因此,與傳統製程的複雜度與高成本相比下,仍具有一定的優勢與發展潛力,有機會實際應用於業界。
闢鍵詞:氣溶膠噴射列印技術、重新佈線層、奈米銀顆粒墨水、燒結溫度、打線接合焊墊丶可靠度測試
Abstract
In this study,
Aerosol Jet printing (AJP) was successfully used to replace, the
traditional process to complete the multi-layer RDL structure package,
and it was proved to be feasible. This study utilizes solvent to
adjust the concentration of nanoparticles silver ink, and the result
proves that the ink has good atomization and stability when the ratio
of silver ink and solvent is 2:1 (Ag: PGME). The high-quality silver
lines can be successfully printed with the proper parameters of sheath
gas and atomizing gas flow rate, and the line width can be controlled
at 20-30 um according to requirements. The silver ink has good
electrical conductivity, transmission stability and adhesion after
sintering at a temperature above 180°C for 1 hour by direct
temperature sintering method. The minimum average resistivity reaches
2.22 x 10-6 cm, about 2 times that of bulk silver, and the adhesion
grade reaches 5B. In addition, the adhesion of silver ink was also
enhanced by adding polymer ink, which has obvious effect and can
further improve the adhesion of silver ink.
This study
utilizes the silver ink printing parameters obtained above to print
single-layer RDL and multi-layer RDL structures, and conduct wire
bonding and shear-pull test verification through different layers of
silver pads. The results demonstrate that the printed silver circuits
and bond pads are repeatable, with line widths and pad sizes of
approximately 25-28 um and 100-110 um, respectively. The multi-layer
RDL structure with added polymer layer can achieve 100% wire bonding
yield rate when has only one silver bond pad, and can pass the
standard value of the shear-pull test specification.
However, the silver bond pads of the
single-layer RDL structure need to be printed to three layers to
achieve the same strength. It shows that the wire bonding yield rate
and the force strength of the gold ball are affected by the thickness
of the silver bond pad andthe polymer layer: Furthermore, we printed
800 multi-layer RDL structure packages with three-layer silver bond
pads for Reliability testing (RA). The study results show that the RDL
package has good reliability in normal temperature and humidity and
high-low temperature environments, and the vield rate of the
Temperature cycle test (TCT) and High temperature storage test (HTSL)
can reach 100%. However, when the humidity is increased to above
85%RH, the reliability of the RDL package is reduced due to the pores
and defects between the layers. The yield rate of Highly accelerated
stress test (HAST) dropped to 96%, and the yield rate of Pressure cook
test (PCT) with 100% RH dropped to 76%.
Finally, after a
comprehensive evaluation and analysis, although the production speed
of AJP technology is still lower than the traditional process, there
are still many equipment and cost
issues to be considered before the actual mass production application.
However, due to its advantages of mask-free
direct structure printing, wide range of material selection and less
chemical waste, and this study has proved that it has technical
feasibility and reliability, it can be successfully applied to the
manufacture of RDL structure packages. Therefore, compared with the
complexity and high cost of the traditional process, AJP still has
certain advantages and development potential, and has the opportunity
to be practically applied in the industry.
Keywords: Aerosol Jet printing
technology, redistribution layer, nanoparticles silver ink, sintering
temperature, wire bonding pad, reliability test
|