【摘要】：激光加工具有非接觸加熱、加熱對象快速升溫、不同材質(zhì)升溫效果不同的特性,對單個焊點加工效率高于傳統(tǒng)加工方法。而激光由于加熱效果明顯受到激光器參數(shù)(波長、頻率等)的影響,這為激光加工引入不穩(wěn)定因素。激光軟釬焊作為新興的焊接方式,具有高效的優(yōu)點,也伴隨許多實際問題。激光對焊點的加熱效果受到材料特性得影響,不同材質(zhì)對激光的吸收率不同,這也引入了焊接效果難以控制的風(fēng)險。焊接過程時間短,在過程中產(chǎn)生的缺陷如下:助焊劑裂解和炭化,潤濕不良,內(nèi)部融合不充分,焊接過程不平穩(wěn),這些缺陷都會影響到焊點質(zhì)量。因此,研究制訂能消除上述缺陷的工藝方案,對企業(yè)提高生產(chǎn)效率具有現(xiàn)實意義。此外,由于激光加工尚未在電子組裝領(lǐng)域廣泛應(yīng)用,對焊點的成型質(zhì)量的評價工作不完善,因此,企業(yè)清晰了解到激光軟釬焊和傳統(tǒng)方式下的焊點質(zhì)量的差異性,對于開發(fā)激光加工設(shè)備也具有重大的幫助。針對生產(chǎn)過程中的典型焊接缺陷進行觀察,歸納出四種典型的缺陷形式,并對其產(chǎn)生機理進行分析。燒損現(xiàn)象主要出現(xiàn)在焊點表面或焊點附近的PCB基材上,和助焊劑的燒損有較大關(guān)系;送錫過程的剛性碰撞現(xiàn)象,和工藝曲線中的峰值溫度和時間的配合關(guān)系有關(guān);內(nèi)部氣孔的產(chǎn)生,和助焊劑受熱后的劇烈運動以及母材情況有關(guān);焊點內(nèi)部及表面縮孔現(xiàn)象,和冷卻過程的速率過快有關(guān)。針對現(xiàn)象分析產(chǎn)生機理,結(jié)合機理提出了相應(yīng)的工藝改進方案,成功實現(xiàn)對工藝區(qū)間的優(yōu)化并消除了上述四種缺陷,順利獲得了外觀良好、內(nèi)部充分融合的通孔插裝焊點,此種工藝研究方式和方法對企業(yè)具有較大的指導(dǎo)意義。此外,多數(shù)企業(yè)尚未對激光軟釬焊點的服役性能提出較為系統(tǒng)的評價,業(yè)內(nèi)對激光焊的質(zhì)量評價尚未形成標準化體系。本課題中,對焊點形貌和力學(xué)性能進行觀察發(fā)現(xiàn)激光焊和波峰焊的焊點IMC形貌差異較大,激光焊點具有明顯針狀特性,對于提升力學(xué)性能很有幫助。二者斷裂方式有較大差異,波峰焊主要沿引腳方向開裂,激光焊點主要在孔壁處開裂。對焊點在環(huán)境試驗中的性能變化進行觀察,發(fā)現(xiàn)熱沖擊后激光焊點IMC形貌針狀消失,趨于平滑,高溫高濕條件明顯促進IMC生長。每種試驗條件下,激光焊點的力學(xué)性能均優(yōu)于波峰焊點,呈現(xiàn)出明顯優(yōu)勢。通過上述兩種試驗,讓企業(yè)對插裝焊點的激光加工效果獲得清晰的認知,也為提升優(yōu)化焊點服役能力的工作做好理論鋪墊,同時為焊接質(zhì)量的評價體系構(gòu)建提供數(shù)據(jù)參考。
[Abstract]:Laser machining has the characteristics of non-contact heating, rapid heating of heating objects and different heating effects of different materials. The processing efficiency of single solder joint is higher than that of traditional processing methods. The laser heating effect is obviously affected by the laser parameters (wavelength frequency etc.) which introduces unstable factors for laser processing. As a new welding method, laser soldering has the advantages of high efficiency and many practical problems. The effect of laser heating on the solder joint is affected by the properties of the material, and the absorptivity of the laser is different with different materials, which also leads to the risk that the welding effect is difficult to control. The defects in the welding process are as follows: flux cracking and carbonization, poor wetting, inadequate internal fusion and unsteady welding process, all of which will affect the quality of solder joint. Therefore, it is of practical significance for enterprises to improve production efficiency by studying the process scheme which can eliminate the above defects. In addition, because laser processing has not been widely used in the field of electronic assembly and the evaluation of the forming quality of butt joint is not perfect, enterprises clearly understand the difference between laser soft brazing and traditional solder joint quality. It is also of great help to the development of laser processing equipment. Based on the observation of typical welding defects in production process, four typical defects were concluded and the mechanism of their formation was analyzed. The phenomenon of burning loss mainly occurs on the surface of solder joint or on PCB substrate near solder joint, which is related to the burning loss of flux, and the rigid collision phenomenon of tin feeding process is related to the coordination of peak temperature and time in the process curve. The formation of internal pores is related to the violent movement of flux after heating and the phenomenon of shrinkage of solder joints and surface, which is related to the rate of cooling process. According to the mechanism of phenomenon analysis and combining with the mechanism, the corresponding process improvement scheme is put forward. The process interval is optimized and the four defects mentioned above are eliminated successfully. The solder joint with good appearance and full internal fusion is obtained successfully. This process research method and method have great guiding significance to the enterprise. In addition, most enterprises have not yet proposed a systematic evaluation of the service performance of laser soldering joints, and a standardized system has not been formed for the quality evaluation of laser soldering in the industry. In this paper, the morphology and mechanical properties of solder joint were observed. It was found that the IMC morphology of laser welding and wave welding were different, the laser solder joint had obvious needle-like characteristics, which was helpful to improve the mechanical properties. There is a great difference in fracture mode between them. The wave peak welding mainly cracks along the pin direction, and the laser solder joint cracks mainly at the hole wall. The changes of the properties of solder joints in environmental tests were observed. It was found that the morphology of laser welded joint IMC disappeared after thermal shock and tended to smooth. The growth of IMC was promoted by high temperature and high humidity. Under each test condition, the mechanical properties of laser solder joint are better than that of wave peak solder joint, showing obvious advantages. Through the above two kinds of experiments, the enterprises can get a clear understanding of the laser processing effect of the intercalation solder joint, and also make a good theoretical foundation for improving the service ability of the solder joint, and provide the data reference for the construction of the welding quality evaluation system at the same time.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN05

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