- 學位論文
應用田口法改善封裝的VFBGA晶片金線損壞率之研究
The study of Improving the Damage Percentage of Gold Wire in the Molded VFBGA Chips using the Taguchi Method
摘要
本實驗研究著重於現有製程的超微細球柵陣列封裝 (VFBGA)，於壓注轉移成型封裝製程中發生金線損壞缺陷，運用田口法之平均數分析 (ANOM) ，針對VFBGA晶片微電子封裝製程獲得最小的金線損壞率。可得知最佳化封裝條件包括：(1)基板預熱溫度177 ℃、(2)兩段式模具施加壓力 (第一段施加壓力9 Ton及第二段全施加壓力28 Ton)，(3)模具溫度180 ℃，以及(4)下模模具真空孔孔數20孔。 由實驗獲得最佳化封裝條件，再次進行可靠度確認性實驗證實可降低金線之平均損壞率至0.02 %。運用田口法之變異數分析 (ANOVA) ，來決定實驗研究的每一個控制因子所占的貢獻百分比。由於目前尚未有研究發現模具之真空孔孔數不足而造成金線斷線的機制，在此四個控制因子中，下模模具真空孔數量對於金線損壞是最具有影響力，其貢獻度百分比占了72.14 %。依據最佳化封裝條件及透過修改現有的 VFBGA 晶片封裝製程，統計並比較修改前與修改後 14 批金線損壞數量，其每一批VFBGA晶片數量之金線損壞的最大缺陷百分比，大幅地由1.31% (修改前) 下降至0.12%，且統計共14批VFBGA晶片數量之金線損壞之平均缺陷百分比由1.10%下降至0.12%。
並列摘要
This study focuses on investigating the reduction of gold-wire damage in an existing process of very fine pitch ball grid array (VFBGA) transfer molding. Using analysis of mean (ANOM) of the Taguchi method, the optimum conditions for molding VFBGA microelectronic assembly with very minimal wire damage were obtained. These optimum conditions included: (1) a substrate preheat temperature of 177 , (2) a two-step mold clamping [the first-stage adapted clamp force (9 ton) and a second-stage full clamp force (28 Ton)], (3) a mold temperature of 180 , and (4) a bottom mold vacuum hole number of 20. Under these optimum conditions, a confirmation experiment was carried out, and the average defect percentage of the wire damage decreased to 0.02%. The percentage contribution of each controllable factor within the current investigation range was also determined via ANOVA (analysis of variance) of the Taguchi method. Among the four controllable factors, the number of vacuum hole in a bottom mold was the most influential on the wire damage; its percentage contribution was 72.14% and the mechanism of wire damage due to insufficient vacuum hole was also presented. Through a modification of the existing process of VFBGA transfer molding according to the optimum conditions, its maximum defect percentage of wire damage per sub lot substantially decreased to 0.12% from 1.31% (before modification), and its average defect percentage of wire damage for 14 sub lots decreased to 0.03% from 1.10%.