應用田口方法於高導磁率錳鋅鐵氧磁體T2燒結製程研究

Abstract

在高導磁率錳鋅鐵氧磁體(high permeability Mn-Zn ferrite)的產業中，所有的鐵芯供應商都希望自家鐵芯產品的導磁率都能比競爭者要高以爭取更多的訂單。高導磁率的錳鋅鐵氧磁體材料若能配合適當的T2燒結製程(T2 sintering process)參數控制的燒結電熱爐，則可使燒結後的鐵芯表現出該高導磁率材料所能具有的最高導磁率。除了錳鋅鐵氧磁體粉末的化學組成與物理特性會影響鐵芯導磁率外，錳鋅鐵芯內部的金屬離子價位及微觀結構也是影響鐵芯導磁率的關鍵因素之一。因為T2燒結製程會改變錳鋅鐵芯的金屬離子價位及微觀結構，所以錳鋅鐵芯的導磁率和T2燒結製程的參數水準有著密切關連性。本研究應用田口方法(Taguichi method)的L9(34)直交表與S/N比(signal to noise ratio)之望大特性(large-the-better)來進行T2燒結製程的4個可控因子對導磁率為10000μi的錳鋅鐵氧磁體材料製作的不同尺寸環型鐵芯(toroid core)導磁率的效果實驗，透過選取氣氛參數(atmosphere parameter)、持溫溫度(soak temperature)、持溫時間(soak time)及降溫率(cooling rate)組成的可控因子實驗組合，以得出可提高鐵芯導磁率的最適可控因子水準。實驗結果顯示，適當的可控因子水準組合是能有效提高試樣鐵芯的導磁率。當氣氛參數、持溫溫度、持溫時間與降溫率分別為a0、T0+30℃、t0+105min、CR0+1℃/min，則小尺寸的環型鐵芯之導磁率可達12010μi，又當這4個可控因子分別為a0+0.5、T0℃、t0+105min、CR0℃/min，則大尺寸的環型鐵芯之導磁率可至9791μi。這4個可控因子中，除了持溫區的持溫時間對任何尺寸的鐵芯導磁率都是正向效果外，其它的3個可控因子都會隨鐵芯尺寸的不同而有個別最適的水準條件。因此，欲提高鐵芯導磁率，則必須依據環型鐵芯的尺寸來選擇個別的最適可控因子水準組合。

In the field of high permeability Mn-Zn ferrite, all the manufactures always expect to produce ferrite cores with higher permeability than their competitors for winning the order. If the ferrite cores are composed of high permeability Mn-Zn ferrite material and sintered in the kiln controlled with proper parameters of the T2 sintering process, it will reveal the highest permeability as possible as the instinct of high permeability Mn-Zn ferrite material. Not only the chemical composition and physical property of Mn-Zn ferrite powder affect the core permeability, but also the valence of cations and the microstructure of ferrite core will dominate the permeability. The permeability of Mn-Zn ferrite is closely relative to the T2 sintering process, because the valence of cations and the microstructure of ferrite core strongly depend on the T2 sintering process. The L9(34) orthogonal arrays and S/N ratio (η) for large-the-better of Taguichi methods was applied to study the effects of four control factors of the T2 sintering process, i.e., atmosphere parameter, soak temperature, soak time and cooling rate, on increasing the permeability of toroid cores of different size of high permeability Mn-Zn ferrite material in this paper. The experimental results showed that the permeability of smaller toroids were around 12010 with the optimum combination of a0(atmosphere parameter), T0+30℃(soak temperature), t0+105min(soak time) and CR0+1℃/min(cooling rate), and the permeability of bigger toroids were near to 9791 when the four control factors were a0+0.5, T0℃, t0+105min and CR0℃/min. This study presented that the optimum combinations of the T2 sintering process made the cores with the highest permeability when the optimum combinations were decided by the size of the toroid cores.