高強度、高導電度粉末冶金銅工件之研究

Abstract

隨著電子元件朝輕、薄、短、小的要求發展，單位體積產生的熱量越來越多，越需要使用高導熱性能的材料將產生的熱能傳輸出去，由於銅的導電導熱性能僅次於銀，且價格較低，因此適合作為散熱片的材料，但其機械強度較低，容易變形因而限制了其應用範圍。本研究探討以粉末冶金製程製造銅工件，利用細晶強化、析出硬化以及散佈強化三種不同的強化機制，希望在導電度不減少太多的前提下盡量提高銅的硬度。 在細晶強化方面，利用細銅粉於較低溫度燒結，可以獲得密度為97%，硬度為HV 51，導電度為100 IACS%的銅工件，高於MPIF的規範(密度89%、硬度HV 18、導電度85 IACS%)。 在析出硬化方面，將鉻-銅合金升溫至1050℃燒結並固溶，接著於450℃時效，固溶在銅基材內部的鉻會析出，使導電度上升，且細小的析出物可造成局部的應力場，阻礙差排移動，因此增加了合金的強度，銅-0.7 wt%鉻在時效處理後硬度為HV 109，導電度為86 IACS%，若施以形變、時效處理後硬度為HV 152，導電度為89 IACS%。 在散佈強化方面，探討兩種合金，第一種是鎢-銅合金，鎢和銅互相不固溶，且鎢的硬度高，細小的鎢散佈在銅當中，可以抑制晶粒成長和阻礙差排移動，提高合金的硬度，銅-0.2 vol%鎢合金在950℃燒結完後密度為98%，硬度為HV 57，導電度為99 IACS%。利用再壓再燒可以進一步提高鎢-銅合金各項性質，銅-0.3 vol%鎢合金經過再壓再燒後密度為94%，硬度為HV 60，導電度為92 IACS%，第二種是氧化鋁-銅合金，以高能球磨機球磨銅粉和鋁-銅預合金粉，並且於空氣氣氛中升溫至700℃作內部氧化處理，以生成奈米Al2O3顆粒，粉末經過氫氣還原後再予以升溫燒結，由於 Al2O3顆粒在燒結時能阻礙晶界移動，有助於晶粒細化，能避免硬度與強度於高溫時大幅下降，銅-4.83 vol%氧化鋁(1 wt%鋁)合金經過球磨、內部氧化、還原以及1050℃燒結後，密度為96%，硬度為HV 192，導電度為67 IACS%，而銅-1 vol%氧化鋁(0.2 wt%鋁)合金於950℃燒結後，燒結密度為97%，硬度為HV 178，導電度為76IACS%；銅-0.5 vol%氧化鋁(0.1 wt%鋁)合金於900℃燒結後，燒結密度為99%，硬度為HV 170，導電度為78 IACS%。

As the electronic devices become lighter and smaller, thermal management becomes a big issue. Since copper and copper alloys have high thermal conductivities, these materials have been widely used in these electronic devices. However, copper is soft after sintering, which limits its applications. To solve this problem, methods of grain refinement, precipitation hardening, and dispersion strengthening were used in this study to improve the strength and hardness of press-and-sintered copper alloys without losing much of the electrical and thermal conductivities. Results shows that sintering fine (D50 = 5μm) copper powder at 800℃ for 3 hrs in hydrogen can reach 97% relative density, HV 51 hardness, and 100 IACS% electrical conductivity. For precipitation hardening alloys, copper-0.7 wt% chromium alloys were sintered and solution treated at 1050℃ for 3 hrs in hydrogen. After water quenching and aging at 450℃ for 3 hrs in hydrogen, a hardness of HV 109 and an electrical conductivity of 86 IACS% were obtained. Deforming specimens before aging further increased the hardness to HV 152 and the electrical conductivity slightly increased to 89 IACS%. For dispersion strengthening alloys, wet mixing and high energy milling were used in order to attain uniform distribution of dispersed particles in the copper matrix. Copper-0.2 vol% tungsten alloy sintered at 950℃ for 3 hrs reached HV 57 hardness and 99 IACS% electrical conductivity. Copper-4.83 vol% alumina (1 wt% aluminum) alloy was internal oxidize at 700℃ and sintered at 1050℃ for 3 hrs, and the hardness and electrical conductivity reached HV 192 and 67 IACS%, respectively. Copper-1 vol% alumina (0.2 wt% aluminum) alloys sintered at 950℃ for 3 hrs showed 97% relative density, HV 178 hardness, and 76 IACS% electrical conductivity. Copper-0.5 vol% alumina (0.1 wt% aluminum) alloys sintered at 900℃ for 3 hrs exhibit 99% relative density, HV 170 hardness, and 78 IACS% electrical conductivity.