Low cost & high quality copper wire bonding in increasing market growth

In the current semiconductors industry, there are many advanced packaging technologies available to increase market growth. However, the major selection criteria of optimum technology are normally depending to the factor of cost effectiveness. For the same reason, acceptance and implementation of low cost Copper wire bonding in assembly interconnect has grown from optional to mandatory. Over time, there are many companies still not able to achieve desirable performance, especially without trading off some other performance indices such as quality, capacity, scrap or machine efficiency. If there is any quality issue, all the saving in wire material will become invalid, especially if there are customer claims. The Copper wire bonding quality and challenges are actually tie closely to its two fundamental properties, Copper is harder than bond pad metal and it gets oxidized easily. The bonding of copper wire will require tedious optimization on all elements that described in SIPOC (Supplier, Input, Process, Output and Customer) chart. By complying to the SIPOC, initial stage of development must be started with supplier partnership, recommended method through working workshops and actual bonding process development. With all the material reaching optimum level, bonding process window can be established through comprehensive evaluations and statistical analysis. From all these multiple evaluations, there were many breakthrough findings and solutions obtained. From the perspective of supplier (machine) and input material, there are many risks improvement can be performed on designs and functionalities. The evaluations can be started or equipped with finite element analysis (FEA), high speed video and new innovative methods. In most cases, when optimum process window of Copper wire bonding established, it would require additional bonding cycle time. The loss in cycle time could result in capacity drop in the range of 10% to 30%. This is considered significant if solution for the capacity loss is purchasing additional production machines by 30%. Therefore, recommended actions were tied in to the other considerations such as temperature profile, indexing speed and process fine steps improvement. There are multiple approaches required to study every millisecond contained in the entire cycle time. On the potential quality risk, new process control method would need to be introduced in both development and production mode. New innovative control method would address all the potential risks due to bond pad metal displacement and copper oxidization. Meanwhile, every wire bonder requires upgrade to achieve better mechanical performance in alignment with high requirements of Copper wire bonding process. In creating new bonding process, introduction of robust development can bring significant amount of benefits. With multiple studies, combining leadframe design, material selection (capillary & wire), machine hardware and parameter optimization, a new process window was created. Thi window could be used commonly across all devices with very minimum adjustments. It also turned out to be the mos robust and stable process ever found. Throughout all the improvement activities to convert from Gold to Copper wire bonding, the most significant factor found was mind-se change. The copper wire bonding process does not only require conversion activities, but actually it requires ful development efforts, just like what we have done for gold wire since 50 years ago. The low cost bonding process can really ensure special distinctive advantage in costing increasing market share and motivating overall marke growth.