晶圓測試廠之作業基礎成本系統

Abstract

比起晶圓製造或IC設計等產業，測試業在半導體產業中的競爭相對較為激烈。典型的晶圓測試廠把大部分的投資花在測試服務所需的設備，但由於不同客戶、產品的需求變化多樣，「如何得知每個產品的成本和利潤」對測試服務業來說就顯得更加重要。

本研究以台灣某知名測試服務公司的一個晶圓測試廠為案例，使用作業基礎成本制 (Activity-Based Costing, ABC) 的方法來分析其產品的成本。根據分析結果，測試機台的折舊費用為所有成本中比重最重，其次為人力成本和探針卡成本。根據ABC分析所得出的成本結構，可以幫助管理者聚焦在每個產品的主要成本來源，管理者可以針對不同的主要成本來源，採取不同的控管或改善措施。

若將成本分析的結果配合營收的資訊，即可計算每個產品的利潤率。本研究發現測試設備每時成本（Hourly Cost）對每時價格（Hourly Rate）的比值是影響利潤率的關鍵因素。根據產品的利潤分析，當某一個產品的 (Hourly Cost)/(Hourly Rate) 比值不低於1/3 時，則該產品測試服務的成本很有可能會高於營收。本研究亦提出了數個經驗法則，藉由分析產品成本與利潤所得到的經驗數據，可讓業務人員很迅速但粗略地以 (Hourly Cost)/(Hourly Rate) 估計「利潤率」，並且以「預期利潤率」粗略估計「新產品導入程序完成後，損益兩平的量產下單量」。

In the semiconductor industry, wafer testing business is facing much more rigorous competition than other major subindustries, such as wafer foundries or IC design houses. A wafer testing factory typically puts most of its investment on the cost of the equipments. Due to the diversity of requirements from different customers and products, it becomes very import for a testing service provider to know the cost and the profit for each single product.

This research adopted ABC (Activity-Based Costing) to analyze the cost of several products in a wafer testing factory of one of the leading testing service provider in Taiwan. According to our analyses, the depreciation cost of testing equipments dominates the total cost of a product. Labor cost and probe card cost are the secondary factors. The cost structure derived from ABC analysis can help the managers to focus on the major cost sources for each product, and managers can take different control or improvement actions for different major cost sources.

With the revenue information, the profit rate of each product was derived. This research revealed that the ratio of “Hourly Cost” to “Hourly Rate” is the key factor of the profit rate. According to the product profit analysis, for a product, when the ratio is no less than 1/3, it is more likely that the revenue can not cover the total cost of the testing service. In this research, several rules of thumb are proposed for sales persons to make a quick but rough guess of profit rate (given hourly rate and hourly cost) and break-even production amount after the new product introduction phase (given expected profit rate).