飛秒激光焊接 Al₂O₃ 陶瓷的裂紋特征與接頭性能研究

中圖分類號(hào)：TG456.7 文獻(xiàn)標(biāo)志碼：A

Abstract：Alumina ceramics are widely used in the field of electronic packaging because of their excellent dielectric propertiesand stable physical and chemical properties.However，the large crack tendency of its weld reduces the joint performanceand greatly limits the application of ceramic joints.Inthis paper，afemtosecond laser is used to weld alumina ceramics.The efects of laser beam scanning trajectory，laser power，and scanning speed on weld crack characteristics and joint properties are studied.A clasification method of weld grade based on average crack width is proposed.The results show that compared with ellipse，helix，vertical8characters，and horizontal 8 characters，sinusoidal scanning laser welding alumina ceramics can obtain smaler average crack width and higher shear force.Increasing the laser power and decreasing the scanning speed is beneficial to reduce the average crack width，increase the weld penetration，and then increase the shear force of the joint.The maximum shear force reaches 1980N ，which isabout 61% of the base material shear force.A prediction model of joint shear force based onthe average crack width and penetration depthof the weld is established，and the model'saccuracyis proved by verification experiments.The minimum deviation between the predicted value and the measured value is only 0.45% The research results provide technical guidance and theoretical support for high-performance welding of ceramics.

Key words：ceramics materials;laser beam welding;crack propagation;shear stress; weld penetration

陶瓷材料硬度極高，耐磨性好，高溫下的化學(xué)穩(wěn)定性好，適用于高溫環(huán)境，同時(shí)，其良好的絕緣性能和低介電損耗特性讓其在電子封裝領(lǐng)域中具有巨大的應(yīng)用潛力[1-4].特別是在超高速飛行器應(yīng)用領(lǐng)域中，研究人員需要將特定的電路嵌入飛行器天線的外部，使得飛行器具有透波和隱身特性，這就要求陶瓷接頭必須具有良好的耐高溫性能、氣密性以及穩(wěn)定的機(jī)械和化學(xué)性能.然而陶瓷的高熔點(diǎn)和硬脆性使其難以被加工，目前常用的焊接方式主要是釬焊和固相擴(kuò)散焊等[5-8]， Lu 等在 1350^°C 的溫度下釬焊 Al₂O₃ 陶瓷 30min ，獲得了剪切強(qiáng)度為 125.63± 4.87MPa 的焊接接頭，Song等[0采用Ni作為中間層，在真空爐中以 1000^°C 和 20MPa 的外加載荷下保溫 30min 成功擴(kuò)散連接 ZrC-SiC 復(fù)合材料.上述焊接方式均需整體加熱加壓，工藝條件復(fù)雜，并且長(zhǎng)時(shí)間的加熱加壓容易使內(nèi)部電子元器件因溫升過(guò)高而失效，同時(shí)，采用中間層連接的陶瓷接頭容易隨時(shí)間推移而氧化，存在使用壽命的局限性，此外，接頭通常只能在 600^°C 以下環(huán)境中工作，無(wú)法充分發(fā)揮陶瓷的高溫性能[11-13].

隨著激光技術(shù)的迅猛發(fā)展，它已能夠在常規(guī)環(huán)境下工作，柔性化程度高、能量密度大的激光焊接方式被應(yīng)用到陶瓷焊接上，非接觸式的焊接方式避免了機(jī)械應(yīng)力的產(chǎn)生.然而，高功率激光焊接時(shí)熱沖擊較大，直接焊接陶瓷易產(chǎn)生裂紋，在焊接時(shí)往往需要對(duì)陶瓷進(jìn)行預(yù)熱[14-15]，Riviere和Harris等學(xué)者通過(guò)預(yù)熱的方式得到了裂紋較少的陶瓷……