Effect of Ag on the Co-firing Behaviour of Ferrite and LTCC

本研究主要探討鎳銅鋅-鐵氧磁體、低溫共燒陶瓷以及銀三者共燒時的反應。由於低溫共燒陶瓷為玻璃粉末與陶瓷粉末混粉製成，本研究首先將鐵氧磁體、玻璃粉末與氧化鋁陶瓷粉末各別混合並在高溫燒結，觀察玻璃粉末、氧化鋁陶瓷粉末以及兩者共存下對鐵氧磁體的影響；接下來，將鐵氧磁體、低溫共燒陶瓷及銀粉末混合在高溫燒結後，觀察銀對各材料所造成的影響；最後，由鐵氧磁體、低溫共燒陶瓷以及銀厚膜以不同方式組成多層結構，在經過高溫燒結後，分析其物質擴散的程度及機制，以及不同排列方式造成的影響。試樣主要由掃描式電子顯微鏡觀察微結構，由X光繞射儀進行相鑑定，以超導量子干涉磁量儀及阻抗分析儀量測磁性，元素分布及擴散則利用電子探針微分析儀分析。實驗結果顯示，當鐵氧磁體與氧化鋁共燒時，鋁元素取代鐵氧磁體中的鐵元素，並進而影響其磁性性質；而玻璃相中元素亦有擴散至鐵氧磁體的現象，惟其反應不如氧化鋁陶瓷粉末劇烈，而此離子交換反應導致玻璃的組成改變；以上現象在玻璃相及氧化鋁陶瓷共存時亦存在。對銀金屬的共燒研究中，沒有發現銀對系統中任一相有明顯化學反應，但發現其對低溫共燒陶瓷中的玻璃相在高溫時有明顯擴散反應，該反應推測為離子交換反應，並進而影響低溫共燒陶瓷的組成。從多層結構的研究中，由於鐵氧磁體與低溫共燒陶瓷亦有擴散反應，銀金屬與低溫共燒陶瓷間反應受其催化加速，使低溫共燒陶瓷大量產生第二相結晶，導致銀電極層不完整，影響整體元件完整性。The co-firing behaviour of NiCuZn-ferrite, LTCC and Ag has been investigated in the present study. In order to investigate the effect of each component during co-firing, the glass powder and Al2O3 powder were mixed with ferrite powder and sintered. Then, ferrite powder, LTCC powder and Ag powder were mixed with each other and co-fired. The interactions between Ag and ferrite/LTCC are observed. Several model laminated specimens composing of ferrite, LTCC and Ag layers are also prepared. After co-firing, the interaction and diffusion between each layer are investigated. The microstructure is observed by scanning electron microscopy (SEM). X-ray diffraction (XRD) is used for phase identification. The magnetic properties of the samples are measured by superconducting quantum interference device magnetometer (SQUID) and impedance analyzer. The diffusion is investigated by electron probe micro-analyzer (EPMA). As co-firing Al2O3 with ferrite, Fe3+ ions are substituted by Al3+ ions and the reactant, α-Fe2O3, is formed. Such reaction induces a degradation of magnetic properties. The ions in glass phase also diffuse into ferrite during co-firing, but the extent of reaction is lower comparing to that during co-firing of ferrite and Al2O3. Such ion exchange changes the composition of glass, and induces the precipitation of a second phase. While co-firing of ferrite, glass and Al2O3, theα-Fe2O3 and anorthite phases are also found. The magnetic properties of ferrite are degraded further. The chemical interaction is not found as co-firing Ag with ferrite/LTCC, but a large number of Ag diffuses into glass phase of LTCC during co-firing. Such reaction should be an ion exchange reaction, which change the composition of LTCC. In the laminated specimens, because of the interaction between ferrite and LTCC, the diffusion of Ag into LTCC is possible. Therefore, a larger amount of second phase is precipitated and some may contact the Ag electrode