IC構裝基板佈局電性模擬分析與傳輸特性改良

Abstract

數百MHz的訊號通過基板到印刷電路板上的輸出訊號將呈現什麼反 應？基板的傳輸頻寬有多大？在高頻操作下，串音與擺鈴的問題若不透過模擬預知，錯誤的結果將不可預期，在焊接上IC以後將有一堆Bug解決不完，屆時將分不清是在基板的設計上出了問題，還是晶片設計有問題。因此，我們的模擬將對於基板佈局設計者提供預先的最佳化設計概念，讓晶片串接基板後有最優的表現，可以讓系統在最高的工作頻率下正常運作，提出讓封裝設計者或使用者實際估算出基板的響應特性，進而避免瑕疵，設計出符合需求的傳輸基板藍圖。 本論文使用方波響應來量測傳輸線的表現，在傳輸線的等效電路元件前後級加上CMOS反相器和寄生電容效應一併的模擬，完整且清楚地呈現出訊號從晶片透過基板連接至印刷電路板或介面卡的特性；藉此響應的量測可以得到訊號衰減、延遲、頻寬、擺鈴及串音的大小，便能判斷系統可容許的工作頻率的極限與上昇時間和下降時間的限制，選擇匹配阻抗與採用遮蔽效應與否。 直接對於複雜的基板導線作分析，並沒有辦法給任意基板設計提供充分的幫助，所以我們先將導線變因分離，最後再進一步作整合，欲提出一個多變數集合而成的公式，讓使用者不必透過軟體模擬即可以很迅速的經過估算就知道各種近似的基板響應。

What’s the output signal performance after the input signal with hundreds of mega hertz transmitted through the substrate to the printed circuit board? Does the bandwidth of the transmission line large enough? One can’t predict the shapes of crosstalk and ring operating on the high frequency before simulation. We will have lots of unknown bugs after packaging an IC. It’s diffucult to tell whether the problems come from the design of the substrate layout or the chip. By using our pre- simulation of the substrate layout, one could get the idea of the optimal design and the best IC package performance, such as the promotion of transmission frequency. It makes the IC package has the best performance and work fine at the highest frequency. This thesis offers the formulas for designers and users to estimate the transmission response and produce suitable substrate layout blueprint. In this thesis, the transmission response of square-wave is used to criticize the performance of the transmission line. The simulation object includes the CMOS signal output inverter, the transmission line, the parasitic capacitance, and the input CMOS inverter. The circuit is equivalent to the output stage of an IC chip, the connecters on the substrate, and the input stage of another IC. From the equivalent circuit, the signal attenuation, transmission delay, bandwidth, ring, and crosstalk have been measured and used to determine the maximum transmission frequency, the limitation of rise time and fall time, impedance matching, and the shielding consideration. The analysis to the layout of certain substrate can’t be used directly to predict the transmission behavior of other layout. To arise the prediction formulae, the integration of multi-variables of the characteristic of transmission lines is developed in this thesis. We propose a handy method that one can use it to generate the general characteristics formulae from some of the obtained data. This method can save much measuring time for users and still provide the satisfactory data of transmission response in various layout design.