201141332 六、發明說明： 【發明所屬之技術領域】 [0001 ] 本發明涉及一種能節省差分訊號對佈線空間之印刷電路 板及其佈線方法。 【先前彳如标】 [0002] 串擾是指一個訊號於傳輸通道上傳輸時，因電磁耦合而 對相鄰近之傳輸線產生之影響，其表現為於被干擾之訊 號上注入了一定之耦合電壓與耦合電流。於數位電路之 設計領域中，串擾之存於是極為廣泛且隨著訊號速率之 提高與產品外型尺寸越來越小，數位系統總串擾亦急劇 增加，過大之串擾會影響到系統之性能，甚至引起電路 之誤觸發，導致系統無法正常工作。 [0003] 為了解決上述問題，業界通常採用增大訊號線之間距來 降低串擾，從而使得訊號眼圖波形中眼寬與眼高均達到 較大值。然而訊號線間距之增大必然佔用較大之佈線空 間，導致印刷電路板之佈線密度較低，不符合現今資訊 產品體積越來越小之趨勢。 【發明内容】 [0004] 鑒於以上内容，有必要提供一種能節省差分訊號對佈線 空間之印刷電路板及其佈線方法。 [0005] 一種印刷電路板之佈線方法，包括步驟：於所述印刷電 路板上提供一訊號層及位於該訊號層上之兩差分訊號對 ;確定一第一距離，當所述兩差分訊號對之間之距離大 於所述第一距離時，所述兩差分訊號對之訊號輸出端之 眼圖波形中之眼寬或眼高接近不變，且當所述兩差分訊 099115207 表單編號A0101 第4頁/共24頁 0992026926-0 201141332 號對之間之距離小於所述第一距離時，所述兩差分訊號 對之訊號輸出端之眼圖波形中之眼寬或眼高變小；及於 小於所述第一距離之範圍内確定一使得兩差分訊號對之 訊號輸出端之眼寬與眼高符合差分佈線對眼圖要求之第 二距離，將所述兩差分訊號對之間之距離設置為所述第 二距離。 [0006] —種印刷電路板，其包括一訊號層，所述訊號層上佈設 兩差分訊號對，所述兩差分訊號對之訊號輸出端之輸出 _ 訊號眼圖波形中之眼寬或眼高隨兩差分訊號對之間之距 〇 離之改變而改變，當所述兩差分訊號對之間之距離為一 第一距離時，所述兩差分訊號對之訊號輸出端之眼圖波 形中之眼寬或眼高達到最大值，兩差分訊號對之間之距 離為一小於所述第一距離之第二距離，所述兩差分訊號 對之訊號輸出端之眼圖波形中之眼寬與眼高符合差分佈 線對眼圖之要求。 [0007] 與習知技術相比，使用上述印刷電路板及其佈線方法將 〇 兩差分訊號對之間之距離設為所述第二距離，使得輸出 訊號眼圖波形中之眼寬或眼高符合差分佈線對眼圖之要 求，節省了印刷電路板中差分訊號對之佈線空間。 【實施方式】 [0008] 請參照圖1，一印刷電路板1 00包括自上而下順次排列之 一第一接地參考層10、一第一絕緣層20、一訊號層30、 一第二絕緣層40及一第二接地參考層50。所述訊號層30 上佈設至少兩差分訊號對31，每一差分訊號對31包括一 第一訊號線311及一第二訊號線312。每一相鄰之兩第一 099115207 表單編號A0101 第5頁/共24頁 0992026926-0 201141332 訊號線311及第二訊號線312之間佈設有絕緣材料。其中 ，每一第一訊號線311之寬度、厚度、長度分別為w、τ、 L，每一第二訊號線312之寬度、厚度、長度分別與第一 訊號線311之寬度、厚度、長度相等。每一差分訊號對31 之第一訊號線311與第二訊號線312之間之間距為s。兩差 分訊號對31之間之間距為DS。所述第一絕緣層2〇 '第二 絕緣層40及訊號層30之總體厚度為Η。所述第一絕緣層2〇 與第二絕緣層40之厚度相等。 [0009] [0010] 099115207 於一實施例中，每一差分訊號對31之第一訊號線311與第 二訊號線312之寬度W為4密耳、厚度Τ為1· 2密耳、長度L 為12英寸，每一差分訊號對31之第一訊號線311與第二訊 號線312之間之間距S為8密耳。所述第一絕緣層2〇、訊號 層30與第二絕緣層40之總體厚度Η為13. 2密耳，所述第 一絕緣層20與第二絕緣層4〇之介電常數為4·ι。其中每一 差分訊號對31之第一訊號線311與第二訊號線312之間之 間距S為一固定值，為滿足差分訊號對特激阻抗之要求， 其由第一訊號線311與第二訊號龜312之寬度w、厚度τ、 第一絕緣層20、訊號層30與第二絕緣層4〇之總體厚度 第一絕緣層20與第二絕緣層4〇之介電常數等共同決定。 將一訊號發生器分別同每一差分訊號對31之輸入端相連 ’同時將-示波器同每分訊號對31之輸出端相連。 所述訊號發生器之資料傳輸率為5.2比特/秒，所述示波 器端接收資料之誤碼率為1Ε_12。 請參閱圖2與圖3，分別為採用無損對稱帶狀線差分對與 有損對稱帶狀線差分對時遠端串擾與間距D s之關係之波 0992026926-0 表單編號A0101 第6頁/共24頁 [0011] 201141332 形圖。其中每一差分訊號對31之輸出端還電性連接一阻 值為50歐姆之負載。由圖2可知，當間距DS大於10密耳時 遠端串擾接近零。而當間距DS小於1〇密耳時遠端串擾迅 速上升。由圖3可知，當間距DS大於15密耳時遠端串擾接 近零。而當間距DS小於15密耳時遠端串擾迅速上升，當 間距DS為10密耳時遠端串擾為0.34%，仍然符合差分佈 線對串擾之要求。圖3中差分對之損耗因數為0. 02。 [0012] 請參閱圖4與圖5，測試時改變兩差分訊號對31之間之間 q 距為DS，則可得到圖4中眼圖波形中眼寬與間距DS之關係 圖’以及圖5中眼高與間距DS之關係圖。 [0013] 請參閱圖4，該間距DS具有一第一距離可使ΐ艮圖波形中之 眼寬達到最大值，於本實施例中該第一距離為15密耳。 同時當所述兩差分訊號對31之間之距離大於所述第一距 離時，所述兩差分訊號對31之訊號輸虫端之眼圖波形中 之眼寬幾乎不變，且當所述兩差分訊號對31之間之距離 小於所述第一距離時，所述兩差分訊號對31之訊號輸出 Ο 端之眼圖波形中之眼寬變小。該間距DS還具有一大於該 第一距離之第三距離，該第三距離對應之眼寬與第一距 離對應之眼寬相等。於本實施例中該第三距離為20密耳 。所述眼圖波形中眼寬與間距DS之關係圖大致為一雙曲 正切曲線，該雙曲正切曲線有一第一臨界點A。所述第一 臨界點A對應之兩差分訊號對31之間之間距DS為一第一臨 界距離。於該第一臨界點A處對應之眼寬剛好符合差分佈 線對串擾之要求，而該第一臨界點A左侧之其他點不符合 差分佈線對眼圖之要求。於本實施例中該第一臨界距離 099115207 表單編號A0101 第7頁/共24頁 0992026926-0 201141332 為1 0密耳。由此將該間距DS設置為一第二距離，該第二 距離大於或等於所述第一臨界距離，小於或等於所述第 一距離。於習知之佈線中通常會採用增大訊號線之間距 來增大眼寬，即採用第三距離20密耳作為間距DS。於本 發明之實施例中採用所述第一臨界距離後即可節省 20-10 = 10密耳之佈線空間，大大減小了印刷電路板之體 積。 [0014] 請繼續參照圖5，該間距DS具有一第四距離可使眼圖波形 中之眼高達到最大值，於本實施例中該第四距離為15密 耳。同時當所述兩差分訊號對31之間之距離大於所述第 四距離時，所述兩差分訊號對31之訊號輸出端之眼圖波 形中之眼高幾乎不變，且當所述兩差分訊號對31之間之 距離小於所述第四距離時，所述兩差分訊號對31之訊號 輸出端之眼圖波形中之眼高變小。該間距DS還具有一大 於該第四距離之第五距離，該第五距離對應之眼高與第 四距離對應之眼高相等。於本實施例中該第五距離為20 密耳。所述眼圖波形中眼高與間距DS之關係圖大致為一 雙曲正切曲線，該雙曲正切曲線有一第二臨界點B。所述 第二臨界點B對應之兩差分訊號對31之間之間距DS為一第 二臨界距離。於該第二臨界點B處對應之眼高剛好符合差 分佈線對串擾之要求，而該第二臨界點B左侧之其他點不 符合差分佈線對眼圖之要求。於本實施例中該第二臨界 距離為1 0密耳。由此將該間距DS設置為一第二距離，該 第二距離大於或等於所述第二臨界距離，小於或等於所 述第四距離。於習知之佈線中通常會採用增大訊號線之 099115207 表單編號A0101 第8頁/共24頁 0992026926-0 201141332 [0015] Ο [0016] 〇 [0017] [0018] 間距來增大眼寬，即採用第五距離20密耳作為間距DS。 於本發明之實施例中採用所述第二臨界距離後即可節省 20-10 = 10密耳之佈線空間，大大減小了印刷電路板之體 積。通常情況下眼寬對應之第二距離與眼高對應之第二 距離近似相等，當眼寬對應之第二距離與眼高對應之第 二距離不相等時該第二距離設置為二者中之較大值。 則藉由本發明，於印刷電路板100上佈設兩差分訊號對31 時，可將兩差分訊號對之間之距離設定於10〜15密耳之間 ，這樣不僅降低了差分訊號對之間之串擾，且節省了大 量之佈線空間。 於另一實施例中，每一差分訊號對31之第一訊號線311與 第二訊號線312之寬度W為4密耳、厚度Τ為1. 2密耳、長 度L為12英寸。每一差分訊號對31之第一訊號線311與第 二訊號線312之間之間距S為8密耳。所述第一絕緣層20、 訊號層30與第二絕緣層40之總體厚度Η為13. 2密耳，所 述第一絕緣層20與第二絕緣層40之介電常數為4. 1。每一 差分訊號對31之第一訊號線311與第二訊號線312經過預 加重處理以減少碼間干擾，從而增大眼圖波形中之眼寬 與眼高。 將一訊號發生器分別同每一差分訊號對31之輸入端相連 ，同時將一示波器同每一差分訊號對31之輸出端相連。 所述訊號發生器之資料傳輸率為5. 2比特/秒，所述示波 器端接收資料之誤碼率為1Ε-12。 請參閱圖6與圖7，測試時改變兩差分訊號對31之間之間 099115207 表單編號Α0101 第9頁/共24頁 0992026926-0 201141332 距為DS，則可得到圖4中眼圖波形中眼寬與間距DS之關係 圖，以及圖5中眼高與間距DS之關係之圖。 [0019] 請參閱圖6，該間距DS具有一第一距離可使眼圖波形中之 眼寬達到最大值，於本實施例中該第一距離為15密耳。 同時當所述兩差分訊號對31之間之距離大於所述第一距 離時，所述兩差分訊號對31之訊號輸出端之眼圖波形中 之眼寬或眼高幾乎不變，且當所述兩差分訊號對31之間 之距離小於所述第一距離時，所述兩差分訊號對31之訊 號輸出端之眼圖波形中之眼寬或眼高變小。該間距DS還 具有一大於該第一距離之第三距離，該第三距離對應之 眼寬與第一距離對應之眼寬相等。於本實施例中該第三 距離為20密耳。所述眼圖波形中眼寬與間距DS之關係圖 為一雙曲正切曲線，該雙曲正切曲線有一第三臨界點C。 所述第三臨界點C對應之兩差分訊號對31之間之間距D S為 一第三臨界距離。於該第三臨界點C處對應之眼寬剛好符 合差分佈線對眼圖之要求，而該第三臨界點C左側之其他 點不符合差分佈線對眼圖之要求。於本實施例中該第三 臨界距離為10密耳。由此將該間距DS設置為一第二距離 ，該第二距離大於或等於所述第三臨界距離，小於或等 於所述第一距離。於習知之佈線中通常會採用增大訊號 線之間距來增大眼寬，即採用第三距離20密耳作為間距 DS。於本發明之實施例中採用所述第三臨界距離後即可 節省2 0 -1 0 = 1 0密耳之佈線空間，大大減小了印刷電路板 之體積。 [0020] 請繼續參照圖7，該間距DS具有一第四距離可使眼圖波形 099115207 表單編號A0101 第10頁/共24頁 0992026926-0 201141332 中之眼高達到最大值，於本實施例中該第四距離為15密 耳。同時當所述兩差分訊號對31之間之距離大於所述第 四距離時，所述兩差分訊號對31之訊號輸出端之眼圖波 形中之眼高幾乎不變，且當所述兩差分訊號對31之間之 距離小於所述第四距離時，所述兩差分訊號對31之訊號 輸出端之眼圖波形中之眼高變小。該間距DS還具有一大 於該第四距離之第五距離，該第五距離對應之眼高與第 四距離對應之眼高相等。於本實施例中該第五距離為20 密耳。所述眼圖波形中眼高與間距DS之關係圖為一雙曲 〇 正切曲線，該雙曲正切曲線有一第四臨界點D。所述第四 臨界點D對應之兩差分訊號對31之間之間距DS為一第四臨 界距離。於該第四臨界點D處對應之眼高剛好符合差分佈 線對串擾之要求，而該第四臨界點D左側之其他點不符合 差分佈線對眼圖之要求。於本實施例中該第四臨界距離 為10密耳。由此將該間距DS設置為一第二距離，該第二 距離大於或等於所述第四臨界距離，小於或等於所述第 四距離。於習知之佈線中通常會採用增大訊號線之間距 〇 來增大眼寬，即採用第五距離20密耳作為間距DS。於本 發明之實施例中採用所述第四臨界距離後即可節省 20-10 = 10密耳之佈線空間，大大減小了印刷電路板之體 積。通常情況下眼寬對應之第二距離與眼高對應之第二 距離近似相等，當眼寬對應之第二距離與眼高對應之第 二距離不相等時該第二距離設置為二者中之較大值。 [0021] 則藉由本發明，於印刷電路板100上佈設兩差分訊號對時 ，可將兩差分訊號對之間之距離設定於10〜15密耳之間， 099115207 表單編號A0101 第11頁/共24頁 0992026926-0 201141332 這樣不僅降低了差分訊號對之間之串擾，且節省了大量 之佈線空間。 [0022] 藉由上述兩實施例可知，對於相鄰之差分訊號對，於佈 線時先得到眼圖波形中眼寬與相鄰差分訊號對之間距DS 之關係圖，以及眼高與間距DS之關係圖，而後藉由該關 係圖，找出一個合適之間距DS，於該間距DS處，不僅眼 圖波形中之眼寬與眼高均較大，相鄰差分訊號對之間之 串擾較小，且相鄰差分訊號對之間之距離較小，節省佈 線空間。本發明不限在於訊號層30上佈設兩對差分對之 情形，還可於訊號層30上佈設多對間距DS相同之差分訊 號對。 [0023] 綜上所述，本創作確已符合發明專利要求，爰依法提出 專利申請。惟，以上所述者僅為本發明之較佳實施方式 ，舉凡熟悉本發明技藝之人士，爰依本發明之精神所作 之等效修飾或變化，皆應涵蓋於以下之申請專利範圍内 〇 【圖式簡單說明】 [0024] 圖1係本創作印刷電路板較佳實施例之示意圖，該印刷電 路板内佈設至少兩差分訊號對。 [0025] 圖2係本創作印刷電路板中之差分訊號對採用無損對稱帶 狀線差分對時遠端串擾與兩差分訊號對之間之間距之關 係之波形圖。 [0026] 圖3係本創作印刷電路板中之差分訊號對採用有損對稱帶 狀線差分對時遠端串擾與兩差分訊號對之間之間距之關 099115207 表單編號A0101 第12頁/共24頁 0992026926-0 201141332 係之波形圖。 [0027] [0028] [0029] Ο [0030] [0031] Ο [0032] [0033] [0034] [0035] [0036] [0037] [0038] 圖4係採用本創作印刷電路板設計方法一較佳實施例得到 之眼圖波形中眼寬與兩差分訊號對之間之間距之關係之 波形圖。 圖5係採用本創作印刷電路板設計方法一較佳實施例得到 之眼圖波形中眼高與兩差分訊號對之間之間距之關係之 波形圖。 圖6係採用本創作印刷電路板設計方法另一較佳實施例得 到之眼圖波形中眼寬與兩差分訊號對之間之間距之關係 之波形圖。 圖7係採用本創作印刷電路板設計方法另一較佳實施例得 到之眼圖波形中眼高與兩差分訊號對之間之間距之關係 之波形圖。 【主要元件符號說明】 第一接地參考層：10 第一絕緣層：20 訊號層：30 差分訊號對：31 第二絕緣層：4 0 第二接地參考層：50 印刷電路板：100 第一訊號線：311 099115207 表單編號Α0101 第13頁/共24頁 0992026926-0 312 201141332 [0039] 第二訊號線 099115207 表單編號A0101 第14頁/共24頁 0992026926-0201141332 VI. Description of the Invention: [Technical Field of the Invention] [0001] The present invention relates to a printed circuit board capable of saving a differential signal to a wiring space and a wiring method therefor. [Previously as standard] [0002] Crosstalk is the effect of electromagnetic coupling on adjacent transmission lines when a signal is transmitted on a transmission channel. It is characterized by a certain coupling voltage injected into the interfered signal. Coupling current. In the field of digital circuit design, the existence of crosstalk is extremely wide. As the signal rate increases and the size of the product becomes smaller and smaller, the total crosstalk of the digital system also increases sharply. Excessive crosstalk can affect the performance of the system, even Causes the circuit to be triggered by mistake, resulting in the system not working properly. [0003] In order to solve the above problem, the industry generally adopts increasing the distance between signal lines to reduce crosstalk, so that the eye width and the eye height of the signal eye waveform reach a large value. However, the increase of the signal line spacing inevitably occupies a large wiring space, resulting in a low wiring density of the printed circuit board, which does not meet the trend of smaller and smaller information products. SUMMARY OF THE INVENTION [0004] In view of the above, it is necessary to provide a printed circuit board and a wiring method thereof that can save differential signal to wiring space. [0005] A method for wiring a printed circuit board, comprising the steps of: providing a signal layer on the printed circuit board and two differential signal pairs on the signal layer; determining a first distance, when the two differential signals are When the distance between the two differential signals is greater than the first distance, the eye width or the eye height in the eye waveform of the signal output end of the two differential signals is nearly constant, and when the two differential signals are 099115207, the form number A0101 is 4 Page / Total 24 pages 0992026926-0 201141332 When the distance between pairs is less than the first distance, the eye width or eye height in the eye waveform of the signal output end of the two differential signals is smaller; Determining, within a range of the first distance, a second distance between the eye width and the eye height of the signal output end of the two differential signal pairs according to the differential wiring to the eye diagram, and setting the distance between the two differential signal pairs to The second distance. [0006] A printed circuit board comprising a signal layer, wherein the signal layer is provided with two differential signal pairs, and the output of the two differential signals to the signal output terminal is an eye width or an eye height in the signal eye waveform As the distance between the two differential signal pairs changes, when the distance between the two differential signal pairs is a first distance, the two differential signals are in the eye waveform of the signal output end. The eye width or the eye height reaches a maximum value, and the distance between the two differential signal pairs is a second distance smaller than the first distance, and the eye width and the eye in the eye waveform of the signal output end of the two differential signals High compliance with differential wiring requirements for eye diagrams. [0007] Compared with the prior art, the above printed circuit board and its wiring method are used to set the distance between the two differential signal pairs as the second distance, so that the eye width or eye height in the output signal eye waveform is Meets the requirements of differential wiring for eye diagrams, saving wiring space for differential signal pairs in printed circuit boards. [0008] Referring to FIG. 1, a printed circuit board 100 includes a first ground reference layer 10, a first insulating layer 20, a signal layer 30, and a second insulation arranged in this order from top to bottom. Layer 40 and a second ground reference layer 50. At least two differential signal pairs 31 are disposed on the signal layer 30, and each of the differential signal pairs 31 includes a first signal line 311 and a second signal line 312. Each of the two adjacent firsts 099115207 Form No. A0101 Page 5 of 24 0992026926-0 201141332 An insulating material is disposed between the signal line 311 and the second signal line 312. The width, thickness, and length of each of the first signal lines 311 are respectively w, τ, and L. The width, thickness, and length of each of the second signal lines 312 are equal to the width, thickness, and length of the first signal line 311, respectively. . The distance between the first signal line 311 and the second signal line 312 of each differential signal pair 31 is s. The distance between the two differential signal pairs 31 is DS. The total thickness of the first insulating layer 2'' of the second insulating layer 40 and the signal layer 30 is Η. The first insulating layer 2 is equal to the thickness of the second insulating layer 40. [0009] In one embodiment, the width W of the first signal line 311 and the second signal line 312 of each differential signal pair 31 is 4 mils, the thickness Τ is 1.25 mils, and the length L. The distance S between the first signal line 311 and the second signal line 312 of each differential signal pair 31 is 12 mils. The first insulating layer 2, the signal layer 30 and the second insulating layer 40 have a total thickness 13 of 13. 2 mils, and the first insulating layer 20 and the second insulating layer 4 have a dielectric constant of 4· ι. The distance S between the first signal line 311 and the second signal line 312 of each of the differential signal pairs 31 is a fixed value, and the first signal line 311 and the second signal line are required to meet the requirement of the differential signal for the special excitation impedance. The width w, the thickness τ of the signal turtle 312, the total thickness of the first insulating layer 20, the signal layer 30 and the second insulating layer 4, and the dielectric constant of the first insulating layer 20 and the second insulating layer 4 are determined together. A signal generator is connected to the input of each of the differential signal pairs 31. The oscilloscope is connected to the output of each of the signal pairs 31. The data transmission rate of the signal generator is 5.2 bits/second, and the error rate of the received data of the oscilloscope end is 1Ε_12. Please refer to Fig. 2 and Fig. 3, respectively, for the relationship between the far-end crosstalk and the spacing D s using the lossless symmetric stripline differential pair and the lossy symmetric stripline differential pair 0992026926-0 Form No. A0101 Page 6 / Total 24 pages [0011] 201141332. The output of each of the differential signal pairs 31 is electrically connected to a load having a resistance of 50 ohms. As can be seen from Figure 2, the far-end crosstalk is close to zero when the spacing DS is greater than 10 mils. When the spacing DS is less than 1 mil, the far-end crosstalk increases rapidly. As can be seen from Figure 3, the far-end crosstalk approaches zero when the spacing DS is greater than 15 mils. When the spacing DS is less than 15 mils, the far-end crosstalk rises rapidly. When the spacing DS is 10 mils, the far-end crosstalk is 0.34%, which still meets the requirements of the differential distribution line crosstalk. The loss factor of the differential pair in Figure 3 is 0.02. [0012] Referring to FIG. 4 and FIG. 5, when the q-distance between the two differential signal pairs 31 is changed to DS in the test, the relationship between the eye width and the distance DS in the eye waveform of FIG. 4 is obtained, and FIG. 5 The relationship between the height of the middle eye and the distance DS. Referring to FIG. 4, the spacing DS has a first distance to maximize the eye width in the reticle waveform, which is 15 mils in this embodiment. At the same time, when the distance between the two differential signal pairs 31 is greater than the first distance, the eye width in the eye waveform of the signal insomnia end of the two differential signal pairs 31 is almost unchanged, and when the two When the distance between the differential signal pairs 31 is smaller than the first distance, the eye width in the eye waveform of the signal output terminal of the two differential signal pairs 31 becomes smaller. The spacing DS also has a third distance greater than the first distance, the third distance corresponding to the eye width being equal to the eye width corresponding to the first distance. In the present embodiment the third distance is 20 mils. The relationship between the eye width and the spacing DS in the eye waveform is approximately a hyperbolic tangent curve having a first critical point A. The distance between the two differential signal pairs 31 corresponding to the first critical point A is a first critical distance. The corresponding eye width at the first critical point A exactly meets the requirement of the difference distribution line pair crosstalk, and the other points on the left side of the first critical point A do not meet the requirements of the differential wiring for the eye diagram. In the present embodiment, the first critical distance 099115207 Form No. A0101 Page 7 / Total 24 pages 0992026926-0 201141332 is 10 mils. The spacing DS is thus set to a second distance that is greater than or equal to the first critical distance and less than or equal to the first distance. In the conventional wiring, the distance between the signal lines is usually increased to increase the eye width, that is, the third distance 20 mil is used as the spacing DS. By using the first critical distance in the embodiment of the present invention, the wiring space of 20-10 = 10 mils can be saved, and the volume of the printed circuit board is greatly reduced. [0014] With continued reference to FIG. 5, the spacing DS has a fourth distance that maximizes the eye height in the eye waveform, which is 15 mils in this embodiment. At the same time, when the distance between the two differential signal pairs 31 is greater than the fourth distance, the eye height in the eye waveform of the signal output end of the two differential signal pairs 31 is almost constant, and when the two differences are When the distance between the signal pairs 31 is smaller than the fourth distance, the eye height in the eye waveform of the signal output end of the two differential signal pairs 31 becomes smaller. The spacing DS also has a fifth distance greater than the fourth distance, the eye height corresponding to the fifth distance being equal to the eye height corresponding to the fourth distance. The fifth distance in this embodiment is 20 mils. The relationship between the eye height and the pitch DS in the eye waveform is approximately a hyperbolic tangent curve having a second critical point B. The distance between the two differential signal pairs 31 corresponding to the second critical point B is a second critical distance. The corresponding eye height at the second critical point B exactly meets the requirements of the differential wiring for crosstalk, and the other points on the left side of the second critical point B do not meet the requirements of the differential wiring for the eye diagram. In the present embodiment, the second critical distance is 10 mils. The spacing DS is thus set to a second distance that is greater than or equal to the second critical distance and less than or equal to the fourth distance. In the conventional wiring, the 099115207 is used to increase the signal line. Form No. A0101 Page 8 / Total 24 Page 0992026926-0 201141332 [0015] Ο [0017] [0018] The pitch increases the eye width, ie A fifth distance of 20 mils is used as the spacing DS. By using the second critical distance in the embodiment of the present invention, the wiring space of 20-10 = 10 mils can be saved, and the volume of the printed circuit board is greatly reduced. Generally, the second distance corresponding to the eye width is approximately equal to the second distance corresponding to the eye height, and the second distance is set to be the second distance when the second distance corresponding to the eye width is not equal to the second distance corresponding to the eye height. Larger value. According to the present invention, when two differential signal pairs 31 are arranged on the printed circuit board 100, the distance between the two differential signal pairs can be set between 10 and 15 mils, which not only reduces the crosstalk between the differential signal pairs. And save a lot of wiring space. In another embodiment, the first signal line 311 and the second signal line 312 of each differential signal pair 31 have a width W of 4 mils, a thickness Τ of 1.2 mils, and a length L of 12 inches. The distance S between the first signal line 311 and the second signal line 312 of each differential signal pair 31 is 8 mils. The first dielectric layer 20 and the second insulating layer 40 have a dielectric constant of 4.1. The first insulating layer 20 and the second insulating layer 40 have a dielectric constant of 4.1. The first signal line 311 and the second signal line 312 of each differential signal pair 31 are pre-emphasized to reduce inter-symbol interference, thereby increasing the eye width and eye height in the eye waveform. A signal generator is connected to the input of each differential signal pair 31, and an oscilloscope is connected to the output of each differential signal pair 31. The data transmission rate of the signal generator is 5.2 bits/second, and the error rate of the data received by the oscilloscope is 1 Ε-12. Please refer to Fig. 6 and Fig. 7. During the test, change the difference between the two differential signals pair 31. 099115207 Form number Α0101 Page 9/24 pages 0992026926-0 201141332 The distance is DS, then the eye of the eye waveform in Fig. 4 can be obtained. The relationship between the width and the spacing DS, and the relationship between the eye height and the spacing DS in FIG. Referring to FIG. 6, the spacing DS has a first distance to maximize the eye width in the eye waveform, which is 15 mils in this embodiment. At the same time, when the distance between the two differential signal pairs 31 is greater than the first distance, the eye width or the eye height in the eye waveform of the signal output end of the two differential signal pairs 31 is almost unchanged, and When the distance between the two differential signal pairs 31 is smaller than the first distance, the eye width or the eye height in the eye waveform of the signal output end of the two differential signal pairs 31 becomes smaller. The spacing DS also has a third distance greater than the first distance, the third distance corresponding to the eye width being equal to the eye width corresponding to the first distance. In the present embodiment the third distance is 20 mils. The relationship between the eye width and the pitch DS in the eye waveform is a hyperbolic tangent curve having a third critical point C. The distance between the two differential signal pairs 31 corresponding to the third critical point C is a third critical distance. The corresponding eye width at the third critical point C exactly meets the requirements of the differential wiring for the eye diagram, and the other points on the left side of the third critical point C do not meet the requirements of the differential wiring for the eye diagram. The third critical distance in this embodiment is 10 mils. The spacing DS is thus set to a second distance that is greater than or equal to the third critical distance, less than or equal to the first distance. In the conventional wiring, the distance between the signal lines is usually increased to increase the eye width, that is, the third distance 20 mil is used as the spacing DS. By using the third critical distance in the embodiment of the present invention, the wiring space of 20-100 = 10 mil can be saved, and the volume of the printed circuit board is greatly reduced. [0020] Please continue to refer to FIG. 7, the spacing DS has a fourth distance to maximize the eye height in the eye pattern waveform 099115207 Form No. A0101, Page 10/24 pages 0992026926-0 201141332, in this embodiment. The fourth distance is 15 mils. At the same time, when the distance between the two differential signal pairs 31 is greater than the fourth distance, the eye height in the eye waveform of the signal output end of the two differential signal pairs 31 is almost constant, and when the two differences are When the distance between the signal pairs 31 is smaller than the fourth distance, the eye height in the eye waveform of the signal output end of the two differential signal pairs 31 becomes smaller. The spacing DS also has a fifth distance greater than the fourth distance, the eye height corresponding to the fifth distance being equal to the eye height corresponding to the fourth distance. The fifth distance in this embodiment is 20 mils. The relationship between the eye height and the pitch DS in the eye waveform is a hyperbolic tangential curve having a fourth critical point D. The distance between the two differential signal pairs 31 corresponding to the fourth critical point D is a fourth critical distance. The corresponding eye height at the fourth critical point D just meets the requirement of the difference distribution line pair crosstalk, and the other points on the left side of the fourth critical point D do not meet the requirements of the differential wiring for the eye diagram. The fourth critical distance is 10 mils in this embodiment. The spacing DS is thus set to a second distance that is greater than or equal to the fourth critical distance and less than or equal to the fourth distance. In the conventional wiring, the distance between the signal lines is usually increased to increase the eye width, that is, the fifth distance 20 mils is used as the spacing DS. By using the fourth critical distance in the embodiment of the present invention, the wiring space of 20-10 = 10 mils can be saved, and the volume of the printed circuit board is greatly reduced. Generally, the second distance corresponding to the eye width is approximately equal to the second distance corresponding to the eye height, and the second distance is set to be the second distance when the second distance corresponding to the eye width is not equal to the second distance corresponding to the eye height. Larger value. [0021] According to the present invention, when two differential signal pairs are disposed on the printed circuit board 100, the distance between the two differential signal pairs can be set between 10 and 15 mils, 099115207 Form No. A0101, page 11 / total Page 24, 0992026926-0 201141332 This not only reduces crosstalk between differential signal pairs, but also saves a lot of wiring space. [0022] According to the above two embodiments, for the adjacent differential signal pair, the relationship between the eye width and the distance between the adjacent differential signal pairs DS in the eye waveform is obtained first, and the eye height and the spacing DS are obtained. The relationship diagram, and then by the relationship diagram, find a suitable distance DS, at which the eye width and the eye height are larger in the eye waveform, and the crosstalk between adjacent differential signal pairs is smaller. And the distance between adjacent differential signal pairs is small, saving wiring space. The present invention is not limited to the case where two pairs of differential pairs are disposed on the signal layer 30, and a plurality of pairs of differential signals having the same pitch DS may be disposed on the signal layer 30. [0023] In summary, the creation has indeed met the requirements of the invention patent, and the patent application is filed according to law. However, the above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art of the present invention should be included in the following claims. BRIEF DESCRIPTION OF THE DRAWINGS [0024] FIG. 1 is a schematic view of a preferred embodiment of a printed circuit board in which at least two differential signal pairs are disposed. 2 is a waveform diagram of the relationship between the far-end crosstalk and the distance between the two differential signal pairs when the differential signal pair in the printed circuit board of the present invention uses the lossless symmetric stripline differential pair. [0026] FIG. 3 is a diagram showing the distance between the far-end crosstalk and the difference between the two differential signal pairs when the differential signal pair in the printed circuit board of the present invention uses the lossy symmetric stripline differential pair. 099115207 Form No. A0101 Page 12 of 24 Page 0992026926-0 201141332 is a waveform diagram. [0029] [0030] [0031] [0033] [003] [0038] [0038] [0038] FIG. 4 is a method for designing a printed circuit board using the present invention. A waveform diagram of the relationship between the width of the eye and the distance between the two differential signal pairs in the eye waveform obtained in the preferred embodiment. Fig. 5 is a waveform diagram showing the relationship between the eye height and the distance between two differential signal pairs in the eye waveform obtained by the preferred embodiment of the present invention. Fig. 6 is a waveform diagram showing the relationship between the eye width and the distance between two differential signal pairs in the eye waveform obtained by another preferred embodiment of the present invention. Fig. 7 is a waveform diagram showing the relationship between the eye height and the distance between two differential signal pairs in the eye waveform obtained by another preferred embodiment of the present invention. [Main component symbol description] First ground reference layer: 10 First insulation layer: 20 Signal layer: 30 Differential signal pair: 31 Second insulation layer: 4 0 Second ground reference layer: 50 Printed circuit board: 100 First signal Line: 311 099115207 Form number Α 0101 Page 13 / Total 24 page 0992026926-0 312 201141332 [0039] Second signal line 099115207 Form number A0101 Page 14 / Total 24 page 0992026926-0