Additive Manufacture of Metal-Ceramic-Joints by means of Selective Laser Melting

本课题是对电力电子选择性激光熔化金属陶瓷复合材料添加剂生产的研究。目前，陶瓷电路载体主要采用DBC(直接键合铜)或AMB(活性金属钎焊)工艺制造，这两种工艺主要用作电力电子基板材料。这两种工艺都涉及将陶瓷衬底粘接到金属导电层(0.2-0.5 mm)，通常是以薄片的形式。在DCB工艺中，在烧制过程中，通过使铜箔底部熔化的Cu2O与氧化物陶瓷(通常是氧化铝)直接接触来连接这两种材料。1064°C。由于陶瓷和金属化之间的热膨胀系数不同，这一过程产生了粘结键，这在电力电子电路载体的使用中是必需的。在AMB工艺中，添加到焊料合金(通常是Ag-Cu-焊料)中的钛在烧成过程中与陶瓷材料接触时形成反应层。因此，这种焊料充当陶瓷基板和金属箔之间的界面。然而，这两种工艺在灵活性、金属化的3D能力和资源消耗方面都显示出弱点。为了最终保持电路载体的导电结构，需要各种光刻、蚀刻和清洗工艺，这些工艺大大延长了工艺链，并且由于使用了化学物质而对环境造成了额外的损害。选择性激光熔化提供了另一种选择：粉末材料可以选择性地熔化在陶瓷基板上。只需一个工艺步骤即可达到500℃的温度，从而实现最终的金属化。这一过程可以被描述为选择性激光钎焊(SLB)。本课题在分析国内外研究现状的基础上，通过大量的前期工作，选择了以铜钛粉为金属化材料。Al_2O_3将作为基材。在研究项目开始时，将对不含陶瓷基板材料的粉末材料的熔化行为进行鉴定。然而，这项研究的主要目的是确定粉末在加热的氧化铝上的润湿行为以及相关的参数研究。作为鉴定方法，测试了金属化在惰性/真空气氛中进行热后处理前后的附着力试验、载流能力以及长期稳定性。在EDX和WDX分析的基础上，需要回答研究项目的核心问题--通过SLB/SLM产生镁铝相，使含钛粉末与Al_2O_3粘结的可能性。

This project deals with the research of additive production of metal-ceramic composites by means of selective laser melting for power electronics. Currently, ceramic circuit carriers are manufactured using DBC- (direct bonded copper) or AMB- (active metal brazing) processes, that are mostly used as power electronic substrate materials. Both processes involve the bonding of a ceramic substrate to a metallic, electrically conductive thin (0.2-0.5 mm) layer, usually in the form of foils. In the DCB process, the two materials are joined by wetting of the molten Cu2O at the bottom side of the copper foil in direct contact with an oxide ceramic (usually Al2O3) in a firing process at approx. 1064 °C. This process results in a cohesive bond, which is necessary in the use of power electronic circuit carriers due to the CTE differences between ceramics and metallization. In the AMB process, titanium additions to a solder alloy (usually Ag-Cu-solders) form a reaction layer during the firing process in contact with ceramic materials. This solder therefore acts as an interface between the ceramic substrate and a metal foil. However, both processes show weaknesses in the areas of flexibility, 3D capability of the metallization and the consumption of resources. In order to finally preserve the conductive structures of the circuit carrier, various lithography-, etching- and washing-processes are necessary, which significantly extend the process chain and additionally harm the environment by using chemicals. Selective laser melting offers an alternative: powder materials can be selectively melted on ceramic substrates at approx. 500 °C in a single process step, which leads to the final metallization. This process can be described as selective laser brazing (SLB). In this research project, Cu-Ti powder is used as metallization material based on the analysis of the state of the art and the extensive preliminary work carried out. Al2O3 will serve as the substrate material. At the beginning of the research project, the melting behaviour of the powder materials without ceramic substrate material will be qualified. However, the main objective of the research is the determination of the wetting behaviour of the powders on the heated Al2O3 with the associated parameter studies. As qualification methods, adhesion tests, current carrying capabilities as well as long-term stabilities of the metallization before and after a thermal post-treatment in inert / evacuated atmosphere are tested. On the basis of EDX and WDX analyses, the core question of the research project - the possibility of a cohesive connection of titanium-containing powder with Al2O3 in the form of the creation of magneli-phases by means of SLB/SLM - is to be answered.