200952571 九、發明說明： 【發明所屬之技術領域】 本發明係關於一種電路板，尤指一種可傳輸高速差 分訊號之電路板。 【先前技術】 電路板被廣泛的運用於各種電子產品中，用以提供 該等電子產品中電子元件之間的相互電氣連接。隨著電 子產品向高密度、小型化、高可靠性方向發展之需要， 其電子元件之間之連接亦越來越複雜，因此軟性電路板 被越來越廣泛的採用而實現該等連接。 軟性電路板係用柔性之絕緣基材製成之印刷電路 板’具有許多硬性印刷電路板不具備之優點。例如軟性 電路板厚度較薄’可自由彎曲、捲繞、折疊，可依照空 間佈局要求任意安排，並於三維空間任意移動與伸縮， 從而達到元器件裝配與導線連接之一體化，利用軟性電 路板可大大縮小電子產品之體積，因此，軟性電路板於 航空、軍事、移動通訊、手提電腦、電腦週邊、PDA、 數碼相機等領域或產品上得到了廣泛之應用。 因為軟性電路板厚度極薄，軟性電路板上之傳輸線 之阻抗偏低，但傳輸高速訊號要求較高之傳輪線阻抗， 為提高傳輸線阻抗，現有技術中採用之方法係將接地層 參考銅箔蝕刻成網格狀。請參閱第一圖，軟性電路板5〇 之接地層52被㈣成網格狀，電路板50之訊號層上佈 設有-差分訊號對511，其包括兩差分訊號傳輪^ 5 200952571 與513，但於差分訊號傳輸線512與513上傳輸高速差 * 分訊號時，往往會產生較大之共模噪音，影響訊號傳輪 • 品質。 【發明内容】 鑒於以上内容，有必要提供一種可高品質傳送高速 差分訊號之電路板。 一種電路板，包括一訊號層與一接地層’該訊號層 上佈設一差分訊號對’該差分訊號對包括兩條差分訊號 ❹ 傳輸線，該接地層被钮刻而形成複數網格，該複數個網 格由複數條格線圍成’該差分訊號對之兩條差分訊號傳 輸線相對該接地層之一格線或網格之一中心線對稱分 佈。 相較於習知技術，本發明電路板上之差分訊號對之 兩條差分訊號傳輸線相對該接地層之格線或網格之一 中心線對稱分佈，從而減少共模嗓音。 【實施方式】 請參閱圖2及圖3，其為本發明電路板1〇之一較 佳實施例，電路板10包括一訊號層11、一接地層12、 及設於訊號層11與接地層12之間之一層絕緣介質19。 接地層12之銅箔被餘刻成正方形之網格，該等網格由 沿橫向與縱向設置之格線圍成。訊號層11上佈設了三 對差分訊號對111、114與117。 差分訊號對111包括兩條差分訊號傳輸線112與 113，差分訊號傳輸線112與113分佈於接地層12之一 6 200952571 條格線121之兩侧，並相對格線121對稱分佈，因此對 差分訊號對111影響最大之格線為格線121，由於差分 訊號傳輸線112與113相對格線121對稱分佈，從而降 低了差分訊號傳輸線112與113於傳輸高速差分訊號時 之共模噪音。格線121兩側之格線對差分訊號對111亦 有較小之影響，但由於格線121兩侧之格線相對格線 121大致對稱分佈，故其對差分訊號對ηι之影響可大 致抵消。 差分訊號對114包括兩條差分訊號傳輸線115與 116，差分訊號傳輸線115與116分佈於接地層12之兩 相鄰格線122與123之中心線C2之兩侧，並相對中心 線C2對稱分佈，因此對差分訊號對114影響最大之格 線為格線122與123，這兩條格線122與123亦相對中 心線C2對稱分佈，從而降低差分訊號傳輸線115|與n6 於傳輸高速差分訊號時之共模噪音。 差分訊號對117包括兩條差分訊號傳輸線118與 119 ’差分訊號傳輸線118與119分佈於接地層12之正 方形網格之一對角線C3之兩侧，並相對對角線C3對 稱分佈，對角線C3兩侧之格線亦大致相對對角線 對稱分佈，從而降低差分訊號對117之差分訊號傳輸線 118與119於傳輸高速差分訊號時之共模噪音。 «月參閱圖4，其為本發明之另一較佳實施例，一電 路板20之一接地層22之銅箔被蝕刻成正三角形之網 格’該等網格由沿斜向與縱向設置之格線圍成。電路板 7 200952571 20之訊號層上佈設了兩對差分訊號對211與214。 * 差分訊號對211包括兩條差分訊號傳輸線212與 • 213 ’差分訊號傳輸線212與213分伟於接地層22之一 格線221之兩侧，並相對格線221對稱分佈，因此對差 分訊號對211影響最大之格線為格線221 ’由於差分訊 號傳輸線212與213相對格線221對稱分佈，從而降低 差分訊號傳輸線212與213於傳輸高速差分訊號時之政 模噪音。 ~ 春 差分訊號對214包括兩條差分訊號傳輸線215與 ’差分訊號傳輸線215與216分佈於接地層22之正 三角形網格之—中心線C5之兩側，中心線C5為正三 角形網格之頂點到相對邊之巾點之連線，並相對中心線 C5對稱分佈’中心線C5兩侧之格線亦大致相對中心線 C5對稱分佈’從而降低差分訊號對214之差分訊號傳 輸線215與216於傳輸高速差分訊號時之共模噪音。 〇 閱圖5’其為本發明之又一較佳實施例，一電 路板30之一接地層32之銅箱被餘刻成正六邊形之網 格該等網格由格線圍成。電路板30之訊號層上佈設 了兩對差分訊號對311與314。 差刀。凡號對311包括兩條差分訊號傳輸、線312與 313 ’差分訊號傳輪線312與313分佈於接地層32之正 六邊形網格之一 Φ ^ T〜線C6之兩侧，並相對中心線C6 對稱分佈’該中心線C6為穿過正六邊形網格相對之兩200952571 IX. Description of the Invention: [Technical Field] The present invention relates to a circuit board, and more particularly to a circuit board capable of transmitting a high speed differential signal. [Prior Art] Circuit boards are widely used in various electronic products to provide electrical interconnection between electronic components in such electronic products. With the development of electronic products in the direction of high density, miniaturization, and high reliability, the connection between electronic components is becoming more and more complicated, so that flexible circuit boards are more and more widely used to realize such connections. A flexible circuit board is a printed circuit board made of a flexible insulating substrate which has many advantages that a rigid printed circuit board does not have. For example, the flexible circuit board has a thin thickness, which can be freely bent, wound, and folded. It can be arranged arbitrarily according to the spatial layout requirements, and can be arbitrarily moved and expanded in a three-dimensional space, thereby achieving integration of component assembly and wire connection, and utilizing a flexible circuit board. It can greatly reduce the size of electronic products. Therefore, flexible circuit boards have been widely used in aviation, military, mobile communications, laptop computers, computer peripherals, PDAs, digital cameras and other fields or products. Because the thickness of the flexible circuit board is extremely thin, the impedance of the transmission line on the flexible circuit board is low, but the transmission line impedance is required to transmit the high-speed signal. To improve the impedance of the transmission line, the method used in the prior art is to ground the reference layer copper foil. Etched into a grid. Referring to the first figure, the ground plane 52 of the flexible circuit board 5 is meshed, and the signal layer of the circuit board 50 is provided with a differential signal pair 511, which includes two differential signal transmissions ^ 5 200952571 and 513, However, when the high-speed difference* signal is transmitted on the differential signal transmission lines 512 and 513, a large common mode noise is generated, which affects the signal transmission quality. SUMMARY OF THE INVENTION In view of the above, it is necessary to provide a circuit board capable of transmitting high-speed differential signals with high quality. A circuit board includes a signal layer and a ground layer. The signal layer is provided with a differential signal pair. The differential signal pair includes two differential signals 传输 transmission lines. The ground layer is buttoned to form a complex grid. The grid is surrounded by a plurality of grid lines. The two differential signal transmission lines of the differential signal pair are symmetrically distributed with respect to one of the grid lines or a center line of the grid. Compared with the prior art, the two differential signal transmission lines of the differential signal pair on the circuit board of the present invention are symmetrically distributed with respect to the center line of one of the grid lines or the grid of the ground layer, thereby reducing the common mode noise. [Embodiment] Please refer to FIG. 2 and FIG. 3, which are a preferred embodiment of a circuit board 1 of the present invention. The circuit board 10 includes a signal layer 11, a ground layer 12, and a signal layer 11 and a ground layer. One layer of insulating medium 19 between 12. The copper foil of the ground layer 12 is engraved into a square grid surrounded by grid lines disposed in the lateral and longitudinal directions. Three pairs of differential signal pairs 111, 114 and 117 are arranged on the signal layer 11. The differential signal pair 111 includes two differential signal transmission lines 112 and 113. The differential signal transmission lines 112 and 113 are distributed on two sides of one of the ground layers 12, 6 200952571, and are symmetrically distributed with respect to the grid lines 121. Therefore, the differential signal pair is The most influential grid line is the grid line 121. Since the differential signal transmission lines 112 and 113 are symmetrically distributed with respect to the grid line 121, the common mode noise of the differential signal transmission lines 112 and 113 when transmitting the high speed differential signal is reduced. The grid lines on both sides of the grid line 121 also have a small influence on the differential signal pair 111. However, since the grid lines on both sides of the grid line 121 are substantially symmetrically distributed with respect to the grid line 121, the effect on the differential signal pair ηι can be substantially offset. . The differential signal pair 114 includes two differential signal transmission lines 115 and 116. The differential signal transmission lines 115 and 116 are distributed on both sides of the center line C2 of the two adjacent grid lines 122 and 123 of the ground layer 12, and are symmetrically distributed with respect to the center line C2. Therefore, the grid lines that have the greatest influence on the differential signal pair 114 are the grid lines 122 and 123. The two grid lines 122 and 123 are also symmetrically distributed with respect to the center line C2, thereby reducing the differential signal transmission lines 115| and n6 when transmitting high-speed differential signals. Common mode noise. The differential signal pair 117 includes two differential signal transmission lines 118 and 119. The differential signal transmission lines 118 and 119 are distributed on both sides of a diagonal C3 of a square grid of the ground layer 12, and are symmetrically distributed with respect to the diagonal C3. The grid lines on both sides of the line C3 are also symmetrically distributed substantially symmetrically with respect to the diagonal line, thereby reducing the common mode noise of the differential signal transmission lines 118 and 119 of the differential signal pair 117 when transmitting the high speed differential signal. Referring to FIG. 4, which is another preferred embodiment of the present invention, a copper foil of a ground layer 22 of a circuit board 20 is etched into a grid of equilateral triangles. The grids are arranged in an oblique direction and a longitudinal direction. The grid is enclosed. Two pairs of differential signal pairs 211 and 214 are disposed on the signal layer of the circuit board 7 200952571 20 . * The differential signal pair 211 includes two differential signal transmission lines 212 and 213 'differential signal transmission lines 212 and 213 which are distributed on both sides of one of the grid lines 221 of the ground layer 22, and are symmetrically distributed with respect to the grid lines 221, so that the differential signal pairs are The line 211 that affects the maximum is the ruled line 221 ' because the differential signal transmission lines 212 and 213 are symmetrically distributed with respect to the ruled line 221, thereby reducing the political mode noise of the differential signal transmission lines 212 and 213 when transmitting the high speed differential signal. The spring differential signal pair 214 includes two differential signal transmission lines 215 and 'differential signal transmission lines 215 and 216 distributed on both sides of the equilateral triangle mesh of the ground layer 22, and the center line C5 is the vertex of the equilateral triangle mesh. The line to the opposite side of the towel point is symmetrically distributed with respect to the center line C5. The grid lines on both sides of the center line C5 are also symmetrically distributed substantially with respect to the center line C5, thereby reducing the differential signal transmission lines 215 and 216 of the differential signal pair 214. Common mode noise at high speed differential signals. Referring to Figure 5', which is a further preferred embodiment of the present invention, a copper box of a ground plane 32 of a circuit board 30 is engraved into a regular hexagonal grid of such grids. Two pairs of differential signal pairs 311 and 314 are disposed on the signal layer of circuit board 30. Poor knife. The pair 311 includes two differential signal transmissions, and the lines 312 and 313 'the differential signal transmission lines 312 and 313 are distributed on one side of one of the regular hexagonal grids Φ ^ T to C6 of the ground layer 32, and are opposite to each other. Line C6 symmetrically distributed 'The centerline C6 is the opposite of the regular hexagonal grid
個角之中心綠，lb L 、’ 中心線C6兩側之格線亦大致相對中心 8 200952571 線C6對稱分佈，從而降低差分訊號對311之差分訊號 ' 傳輸線312與313於傳輸高速差分訊號時之共模噪音。 ' 差分訊號對314包括兩條差分訊號傳輸線315與 316’差分訊號傳輸線315與316分佈於接地層32之正 六邊形網格之一中心線C7之兩侧，並相對中心線C7 對稱分佈’該中心線C7為穿過正六邊形網格相對之兩 個邊之中心線，中心線C7兩側之格線亦大致相對中心 ❹ 線C7對稱分佈，從而降低差分訊號對314之差分訊號 傳輸線315與316於傳輸高速差分訊號時之共模噪音。 由本發明之發明構思可知，本發明亦可運用在其他 各種類型之電路板上，只要將差分訊號對之差分訊號傳 輪線相對接地層之格線對稱分佈，就可降低差分訊號對 之差分訊號傳輸線於傳輸高速差分訊號時之共模嗓 音’從而實現本發明之發明目的。 【圖式簡單說明】 ❹ 圖1係現有技術中電路板之示意圖。 圖2係本發明一較佳實施例電路板上佈設差分訊號對 之示意圖。 圖3係沿圖2中ΙΙΙ-ΙΠ線之部份剖視圖。 圖4係本發明另一較佳實施例電路板上佈設差分訊號 對之示意圖。 圖5係本發明電又一較佳實施例路板上佈設差分訊號 對之示意圖。 【主要元件符號說明】 9 200952571 * 電路板 10、20、30、50 . 訊號層 11 差分訊號對 111、 114、117、211、214、311、314、 511 112、 113、115、116、118、119、212、 差分訊號傳輸線 213、215、216、312、313、315、316、 ❹ 接地層 512 、 513 12 ' 22 ' 32 ' 52 格線 121、122、123 ' 221 絕緣介質 19 中心線 C2、C5、C6、C7 對角線 C3 10The center of the corners is green, lb L , and the grid lines on both sides of the center line C6 are also symmetrically distributed with respect to the center 8 200952571 line C6, thereby reducing the difference signal of the differential signal pair 311 'the transmission lines 312 and 313 when transmitting the high speed differential signal Common mode noise. The differential signal pair 314 includes two differential signal transmission lines 315 and 316' differential signal transmission lines 315 and 316 distributed on either side of the center line C7 of one of the regular hexagonal grids of the ground layer 32, and symmetrically distributed with respect to the center line C7. The center line C7 is the center line passing through the opposite sides of the regular hexagonal grid, and the grid lines on both sides of the center line C7 are also symmetrically distributed substantially with respect to the center line C7, thereby reducing the differential signal transmission line 315 of the differential signal pair 314 and 316 Common mode noise when transmitting high speed differential signals. It can be seen from the inventive concept of the present invention that the present invention can also be applied to other types of circuit boards, as long as the differential signal pair differential signal transmission line is symmetrically distributed with respect to the ground line of the ground layer, the differential signal pair differential signal can be reduced. The transmission mode is a common mode voice when transmitting a high speed differential signal' to achieve the object of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a circuit board in the prior art. 2 is a schematic diagram showing the arrangement of differential signal pairs on a circuit board in accordance with a preferred embodiment of the present invention. Figure 3 is a partial cross-sectional view taken along line ΙΙΙ-ΙΠ of Figure 2. 4 is a schematic diagram showing the arrangement of differential signal pairs on a circuit board according to another preferred embodiment of the present invention. FIG. 5 is a schematic diagram of a differential signal pair disposed on a road board according to still another preferred embodiment of the present invention. [Main component symbol description] 9 200952571 * Circuit board 10, 20, 30, 50. Signal layer 11 differential signal pair 111, 114, 117, 211, 214, 311, 314, 511 112, 113, 115, 116, 118, 119, 212, differential signal transmission lines 213, 215, 216, 312, 313, 315, 316, 接地 ground layer 512, 513 12 ' 22 ' 32 ' 52 grid lines 121, 122, 123 '221 insulating medium 19 center line C2 C5, C6, C7 diagonal C3 10