本文關(guān)鍵詞： MEMS自組裝 釬料形態(tài)預(yù)測 動態(tài)接觸角 激光重熔 MEMS三維封裝　出處：《哈爾濱工業(yè)大學(xué)》2014年博士論文　論文類型：學(xué)位論文

【摘要】：基于微釬料熔滴表面張力的MEMS部件自組裝技術(shù)能夠自行實現(xiàn)對微機械部件的組裝，形成具有高深寬比的三維復(fù)雜微結(jié)構(gòu)，對微機械部件的制造具有重要意義。與此同時，微液滴的驅(qū)動行為則為MEMS微開關(guān)及微流體器件提供了關(guān)鍵技術(shù)，能夠啟發(fā)新型MEMS器件的研發(fā)。本文基于激光重熔工藝開發(fā)了一種新型的MEMS自組裝技術(shù)，并搭建了高精度的自組裝微操作平臺；通過數(shù)值方法與試驗相結(jié)合對影響自組裝靜平衡位置及精度的各因素進(jìn)行了系統(tǒng)的研究；并基于計算流體力學(xué)方法對自組裝的動態(tài)翻轉(zhuǎn)過程、釬料同微部件之間的流固耦合機制進(jìn)行了深入分析；同時，還首次對固體基板上微釬料熔滴的激光驅(qū)動行為進(jìn)行了探索。 自組裝精度影響因素研究表明，自組裝角度偏差小于2.5o；隨著焊盤尺寸和長寬比的增大，自組裝靜平衡角度越��；同時，自組裝中使用的釬料體積越小，靜平衡角度越小，越利于自組裝系統(tǒng)保持其靜平衡位置；而在假設(shè)完全鋪展?jié)櫇竦那疤嵯拢F料的表面張力及接觸角變化對自組裝靜平衡位置幾乎不會產(chǎn)生影響；在焊盤尺寸／釬料球直徑一定時，其靜平衡位置幾乎相同，這一比值可定義為自組裝尺寸因子η。 對無鉸鏈自組裝結(jié)構(gòu)的能量分析表明，系統(tǒng)具有減小固定和活動微部件之間間距的趨勢（由此提出了“虛鉸鏈”的概念），該趨勢會逐漸隨著活動微部件接近于靜平衡位置而減小，當(dāng)活動微部件達(dá)到靜平衡位置時，間距閉合趨勢消失。針對無鉸鏈結(jié)構(gòu)基于引線鍵合工藝，開發(fā)了一種新型的MEMS自組裝限位結(jié)構(gòu)，在引入該限位結(jié)構(gòu)后，自組裝角度偏差小于0.5o。 基于數(shù)值研究方法探尋了微釬料熔滴的動態(tài)潤濕行為，結(jié)果表明動態(tài)潤濕角模型更適合于對快速潤濕鋪展過程進(jìn)行擬合，隨著潤濕鋪展時間的加大，會降低擬合準(zhǔn)確性。在潤濕鋪展的初期快速鋪展階段，Rw(t)~tn（n=0.32~0.45）關(guān)系能很好的擬合潤濕半徑隨時間的變化，但當(dāng)釬料趨于平衡狀態(tài)時，擬合出現(xiàn)偏差。進(jìn)一步研究表明，釬料的潤濕鋪展過程可以通過兩段Rw(t)~tn關(guān)系進(jìn)行擬合，n值的差異意味著潤濕鋪展機制的轉(zhuǎn)變。 自組裝動態(tài)過程的研究結(jié)果表明，自組裝中釬料熔滴優(yōu)先鋪展翻轉(zhuǎn)的活動微部件，之后才在固定微部件上快速鋪展。翻轉(zhuǎn)過程具有增大同一時刻下釬料熔滴在活動微部件上的動態(tài)接觸角的趨勢，增大潤濕驅(qū)動力，使得活動微部件上熔滴潤濕速率更快，，呈現(xiàn)出優(yōu)先鋪展的不對稱現(xiàn)象。轉(zhuǎn)矩分析表明，自組裝動態(tài)過程中凈轉(zhuǎn)矩Mnet上下振蕩，接觸線的前進(jìn)會加劇Mnet的復(fù)雜性。平衡位置附近，Mnet會一直保持在0值附近波動，且正負(fù)兩邊的波動接近對稱。能量分析表明，自組裝釬料熔滴及微部件動能相對于減少的釬料表面能而言十分微小，能量轉(zhuǎn)換效率較低，大部分能量通過轉(zhuǎn)化為內(nèi)能的方式耗散。 對影響自組裝動態(tài)過程的各因素分析表明，隨著釬料熔滴體積的減小，自組裝翻轉(zhuǎn)的速度也越快；釬料潤濕鋪展速度較慢時，自組裝過程呈現(xiàn)出明顯的“快-慢-快”的三階段，這是釬料不對稱鋪展的結(jié)果。而釬料潤濕鋪展速度較快時，翻轉(zhuǎn)作用對于潤濕力的增強效應(yīng)減弱，釬料熔滴呈現(xiàn)對稱鋪展的趨勢。對于自組裝翻轉(zhuǎn)速度而言，當(dāng)翻轉(zhuǎn)速度較慢時，釬料熔滴自由表面能最低。翻轉(zhuǎn)速度較快時，釬料熔滴自由表面能會出現(xiàn)升高的趨勢，之后隨著固定微部件上接觸線的快速前進(jìn)，又會急劇降低。 最后，使用激光偏置局部加熱方法在開放的固體基板上成功實現(xiàn)了微釬料熔滴的驅(qū)動，熔滴總是向著激光中心一側(cè)（熱端）移動，之后當(dāng)激光束中心線同釬料熔滴對稱中心重合時，熔滴停止前進(jìn)。這同一般的液滴熱致驅(qū)動方向（向冷端移動）正好相反。定性及定量分析結(jié)果表明微釬料熔滴驅(qū)動過程中，Marangoni對流及釬劑蒸汽反沖作用力會推動熔滴向偏離激光束中心一側(cè)移動（冷端），減弱熔滴向激光束中心靠攏的趨勢，釬料熔滴在基板上的熱致潤濕性變化才是驅(qū)動熔滴前進(jìn)的主要機制。
[Abstract]:The MEMS component of micro solder droplet surface tension based on self assembly technology can automatically realize the assembly of micro mechanical components, formed with high aspect ratio of the complex three-dimensional micro structure, has important significance for manufacturing micro mechanical components. At the same time, the driving behavior of micro droplets is MEMS micro switch and microfluidic devices provide a key technology, research can inspire new MEMS devices. In this paper, laser remelting technology developed a new type of self-assembly technology based on MEMS, and built a self assembling high precision micro operation platform; through the combination of experiment and numerical methods on the factors influencing the accuracy of the static equilibrium position and self-assembly were studied; and the computational fluid dynamics method based on dynamic turning process of self-assembly between solder with the micro components coupling mechanism are analyzed; at the same time, but also for the first time on solid substrate The laser driving behavior of the droplet of the solder is explored.
Study on the factors affecting the accuracy of self-assembly showed that self-assembly angle deviation is less than 2.5o; with the pad size and length width ratio increases, the self-assembly of static balance angle is small; at the same time, since the volume of solder used in assembling the smaller static balance angle is smaller, more conducive to the self assembling system to maintain its equilibrium position; in the premise of fully wetting, surface tension and contact angle of the solder has influence on the static equilibrium position is almost not self assembly; in pad size / solder ball diameter, the static equilibrium position is almost the same, this ratio can be defined as self assembling size factor ETA.
The hinge of self-assembled structures of energy analysis shows that the system has reduced the spacing between the fixed and movable micro parts (the trend of "virtual hinge" concept), the trend will gradually decrease with the activities of micro components close to the equilibrium position, when the micro component reaches the equilibrium position, closed distance disappear according to the trend. No hinge wire bonding process based on the development of a new type of MEMS self-assembled limit'structure, in the introduction of the limit structure, self assembling angle deviation less than 0.5o.
Study on numerical method based on exploring the dynamic wetting behavior of micro solder droplet, the results show that the dynamic contact angle model is more suitable for fitting the fast wetting and spreading process, with the increase of wetting and spreading time, will reduce the fitting accuracy. Fast spreading in the early stage of wetting and spreading, Rw (T) ~tn (n=0.32~0.45) can good fitting wetting radius changes with time, but when the solder tends to equilibrium, the fitting deviation. Further study showed that the wetting and spreading process of solder using two Rw (T) by fitting ~tn relation, difference of n value means a change of the wetting and spreading mechanism.
That study of self-assembled dynamic process results in the self-assembly of solder droplet spreading flip priority moving micro parts, only after the fixed micro parts rapid spreading. The turning process with the increasing trend of dynamic contact of solder droplet in micro parts on the angle at the same time, increase the wetting driving force, the activity of micro parts of the droplet wetting rate faster, showing asymmetry priority spreading. Torque analysis showed that the self assembling net torque in the dynamic process of Mnet under oscillation, complexity of the contact line ahead will aggravate Mnet. Near the equilibrium position, Mnet will keep the values fluctuate around 0, and the positive and negative fluctuations on both sides of the nearly symmetric. The energy analysis shows that the self-assembly of solder droplet and micro components can reduce the surface energy of solder is very small relative to the energy conversion efficiency is low, most of the energy is transformed into energy consumption by the way Scattered.
The effect of self assembly factors of dynamic process analysis shows that, with the decrease of solder droplet size, self-assembly turning faster; wetting and spreading speed is slow, the self-assembly process showed significantly in the three phase of "fast slow fast", this is the solder spreading result. And asymmetry wetting and spreading speed, enhance the wetting force effect weakened for the reversal effects of solder droplet, symmetric spreading trend. For self assembling turning speed, when the turnover rate is relatively low, solder droplet surface free energy minimum. Turning speed is faster when the solder droplet free surface can appear increasing trend fast forward, then with the fixed micro parts contact lines, and sharply decreased.
Finally, the use of laser bias local heating method in solid substrate on the successful implementation of the open micro solder droplet, droplet always toward the laser center side (hot end mobile), when the laser beam center line with solder droplet symmetry coincide, droplet stop. This same general droplet heat the actuating direction (move to the cold end) on the contrary. The qualitative and quantitative analysis results show that the micro solder droplet driven process, Marangoni convection and flux of vapor recoil force will push the droplet to deviate from the laser beam center side (Leng Duan), weakened the droplet to move closer to the center of the laser beam, solder droplet on the substrate of thermally induced wettability change is the main driving mechanism of droplet advance.

【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TH-39

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本文編號：1461725