200948234 九、發明說明： 【發明所屬之技術領域】 本發明涉及一種軟性電路板，尤指一種可傳輸高速差 分訊號之軟性電路板。 【先前技術】 軟性電路板係用柔性絕緣基材製成的印刷電路板，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 ❹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，並在三維空間任意移動和伸縮，從而達到元器 件裝配和導線連接之一體化。利用軟性電路板可大大縮小 電子產品之體積，適應電子產品向高密度、小型化、高可 靠性方向發展之需要。因此，軟性電路板在航太、軍事、 移動通訊、手提電腦、PDA、數位相機等領域或產品上得 到了廣泛應用。 ❹ 上因為軟性電路板厚度極薄，軟性電路板上之傳輸線的 阻抗偏低’因為傳輸高速訊號要求較高之傳輸線阻抗，在 軟路板上’即使__般製程可達到最細傳輸線寬度，例 D &爾（1雄、爾=〇·()254毫米）’亦難以達到高速訊 輸線阻抗之要求。 多閱® 1 ’習知技術提高傳輸線阻抗之方法，係將軟 上蚀2 50的接地層㈣切割成網格狀。但如果在訊號層 54對2刀對51時’會因為差分傳輸線52和差分傳輸線 也層銅箱網格排佈不同，導致共模嗓音產生， 〜、、m電路板無法傳輸高速差分訊號之原因。 7 200948234 【發明内容】 鑒於上述内容，有必要提供一種可傳輸高速差分訊號 之軟性電路板。 ' 一種軟性電路板，包括一訊號層，該訊號層之上方和 "下方分別設有一接地層，該訊號層與相鄰之接地層之間均 填充一層絕緣介質，該訊號層上佈設一差分對，該差分對 包括兩條差分傳輸線，每一接地層上與該差分傳輸線豎直 相對之部分為一挖空區域，每一接地層上挖空區域之邊緣 ❹ 分別與其相鄰之傳輸線具有一第一水平間距。 該軟性電路板係在該接地層上，將該差分對之兩傳輸 線豎直對應之兩相鄰接地層部分挖空，避免差分對與相鄰 接地層之間距太近而導致傳輸線阻抗偏低問題之產生。本 發明軟性電路板可傳輸高速訊號，並消除習知技術中網格 化接地層所衍生之共模噪音問題。本發明軟性電路板無需 增加額外成本，只需調整習知佈線方式即可實現。 ❹【實施方式】 請參閱圖2,本發明軟性電路板之較佳實施方式包括一 訊號層10及分別位於該訊號層10上、下之兩接地層30，在 訊號層10及每一接地層30之間填充一層絕緣介質20。一差 分對11包括兩條差分傳輸線12及14，並佈線於該訊號層10 上。每一接地層30上，與該差分傳輸線12及14所豎直相對 之部分作挖空處理，以避免差分對11與相鄰接地層30之間 之豎直距離太近而導致傳輸線阻抗偏低問題之產生，每一 接地層30未挖空之部分與其相鄰差分傳輸線12或14具有一 8 200948234 水平間距dl，圖2中每一接地層30上覆蓋之材料為銅箔，其 中央之矩形挖空區域32即是將接地層30上之銅箔挖空所形 成。在該訊號層10上，該差分對11之兩側平行設置有與差 •分對11長度相等之接地導電材料，本較佳實施方式中該接 '地導電材料為銅箔16，每一接地銅箔16與其對應相鄰之傳 輸線12及14具有一水平間距d2。該水平間距dl和d2根據差 分對11傳輸之訊號不同而不同，該水平間距dl和d2可根據 差分對11傳輸不同訊號時之阻抗要求，考慮軟性電路板上 ®每條差分傳輸線12及14之線寬、兩條差分傳輸線12及14之 間距、訊號層10上接地銅箔16之寬度，經由仿真軟體仿真 後確定。也可不在該訊號層10上佈設接地銅箔，僅通過調 整該水平間距dl來調整該差分傳輸線12及14之阻抗，以實 現高速訊號之傳輸。 若在該軟性電路板上佈設多個差分對，即至少有一個 接地層之上下兩個相鄰訊號層上都佈設有差分對，則在該 © 接地層上具有兩個挖空區域，在實際操作中，為避免一個 差分對之挖空區域對另一個差分對造成影響，而產生雜訊 訊號，該兩個挖空區域相鄰之邊緣之間之水平距離應該不 小於填充在每一訊號層與該接地層之間之絕緣介質厚度之 三倍。 該軟性電路板係在佈設有差分對11之訊號層10之上 下兩相鄰接地層30上，將與差分對11之兩傳輸線12、14 豎直對應之部分挖空，避免差分對11與相鄰接地層30之 間距太近而導致傳輸線阻抗偏低問題之產生，並選擇性地 9 200948234 :=二之16’通過仿真軟體 輸線12或二t: 之部分與其相鄰差分傳 線12、14之欠;平間距dl ’以及該接地銅箱16與傳輪 訊號，並轉二=Γ ί發明軟性電路板可傳輸高迷 工㈣“口技術中網格化接地層 ，題°本發明軟性電路板無需增加額外 知佈線方式即可實現。 Μ /、需調整習 ❹ 利申=1述，本發明符合發明專利要件，爰依法提出專 二“’以上所述者僅為本發明之較佳實 ，： 飾ίίί案技藝之人士，在爰依本發明精神所作之等效： ，或變化，皆應涵蓋於以下之申請專利範圍内。寻效修 【圖式簡單說明】 圖1係習知軟性電路板之結構示意圖。 之結構示意 圖2係本發明軟性電路板較佳實施方式200948234 IX. Description of the Invention: [Technical Field] The present invention relates to a flexible circuit board, and more particularly to a flexible circuit board capable of transmitting a high speed differential signal. [Prior Art] 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 thickness of the flexible circuit board is thin, and it can be freely bent, wound, and folded. It can be arranged arbitrarily according to the space layout requirements, and can be arbitrarily moved and expanded in the three-dimensional space, thereby achieving integration of the component assembly and the wire connection. The use of flexible circuit boards can greatly reduce the size of electronic products and meet the needs of electronic products in the direction of high density, miniaturization and high reliability. Therefore, flexible boards are widely used in aerospace, military, mobile communications, laptops, PDAs, digital cameras, and other fields or products.因为 Because the thickness of the flexible circuit board is extremely thin, the impedance of the transmission line on the flexible circuit board is low. Because the high-speed signal requires a high transmission line impedance, even the __ process can achieve the narrowest transmission line width. For example, D & (1 male, er = 〇 · () 254 mm) ' is also difficult to meet the requirements of high-speed signal line impedance. The method of increasing the impedance of the transmission line by the multi-reading technology is to cut the ground layer (4) of the soft etched layer into a grid. However, if the signal layer 54 pairs 2 pairs 51, 'the difference between the differential transmission line 52 and the differential transmission line is also different, resulting in common mode noise, ~, m board can not transmit high-speed differential signals . 7 200948234 SUMMARY OF THE INVENTION In view of the above, it is necessary to provide a flexible circuit board that can transmit high-speed differential signals. a flexible circuit board comprising a signal layer, a signal layer is disposed above the signal layer and a lower layer, and a signal layer is interposed between the signal layer and the adjacent ground layer, and a difference is arranged on the signal layer For example, the differential pair includes two differential transmission lines, and a portion of each ground layer that is vertically opposite to the differential transmission line is a hollowed out area, and an edge 挖 of the hollowed out area on each ground layer has a transmission line adjacent to the adjacent one. The first horizontal spacing. The flexible circuit board is on the ground layer, and the two adjacent ground layer portions corresponding to the two transmission lines of the differential pair are hollowed out to avoid the problem that the transmission line impedance is low due to the distance between the differential pair and the adjacent ground layer being too close. Produced. The flexible circuit board of the present invention can transmit high speed signals and eliminate the common mode noise problem derived from the grid ground layer in the prior art. The flexible circuit board of the present invention can be realized by adjusting the conventional wiring method without adding extra cost.实施 [Embodiment] Referring to FIG. 2, a preferred embodiment of the flexible circuit board of the present invention includes a signal layer 10 and two ground layers 30 respectively located on the signal layer 10, in the signal layer 10 and each ground layer. A layer of insulating medium 20 is filled between 30. A differential pair 11 includes two differential transmission lines 12 and 14 and is routed to the signal layer 10. On each of the ground layers 30, portions perpendicular to the differential transmission lines 12 and 14 are hollowed out to avoid the vertical distance between the differential pair 11 and the adjacent ground layer 30 being too close, resulting in low transmission line impedance. The problem arises that the portion of each ground layer 30 that is not hollowed out has a horizontal spacing dl of 8 200948234 with its adjacent differential transmission line 12 or 14. The material covered on each ground layer 30 in FIG. 2 is a copper foil with a central rectangle. The hollowed out area 32 is formed by hollowing out the copper foil on the ground layer 30. On the signal layer 10, two sides of the differential pair 11 are disposed in parallel with a grounding conductive material having a length equal to that of the differential pair 11. In the preferred embodiment, the conductive material is a copper foil 16, each grounded. The copper foil 16 has a horizontal spacing d2 from its corresponding adjacent transmission lines 12 and 14. The horizontal spacings dl and d2 are different according to the signals transmitted by the differential pair 11. The horizontal spacings dl and d2 can be based on the impedance requirements of the differential pair 11 for transmitting different signals. Consider each of the differential transmission lines 12 and 14 on the flexible circuit board. The line width, the distance between the two differential transmission lines 12 and 14, and the width of the ground copper foil 16 on the signal layer 10 are determined by simulation software simulation. It is also possible to arrange the grounding copper foil on the signal layer 10 and adjust the impedance of the differential transmission lines 12 and 14 only by adjusting the horizontal spacing dl to achieve high-speed signal transmission. If a plurality of differential pairs are disposed on the flexible circuit board, that is, at least one of the ground layers is provided with a differential pair on the next two adjacent signal layers, then there are two hollowed out areas on the © ground layer, in practice In operation, in order to prevent the hollowed out area of one differential pair from affecting another differential pair, and generating a noise signal, the horizontal distance between adjacent edges of the two hollowed out areas should be not less than filling in each signal layer. Three times the thickness of the dielectric between the ground plane. The flexible circuit board is disposed on two adjacent ground layers 30 above the signal layer 10 on which the differential pair 11 is disposed, and the portions corresponding to the vertical transmission lines 12 and 14 of the differential pair 11 are hollowed out to avoid the differential pair 11 and phase. The problem that the distance between the adjacent formations 30 is too close to cause the transmission line impedance to be low, and selectively 9 200948234 := 2 of 16' through the simulation software transmission line 12 or part of the two t: and its adjacent differential transmission line 12, 14 owes; flat spacing dl 'and the grounding copper box 16 and the transmission signal, and turn two = Γ ί invented the flexible circuit board can transmit high-constrained (four) "mesh technology in the grid grounding layer, the problem of the softness of the invention The circuit board can be realized without adding additional wiring. Μ /, need to adjust the Xi Li, the application of the invention is in accordance with the requirements of the invention patent, and the second is based on the law. Indeed, the equivalent of the singularity of the singularity of the invention, or variations, should be covered by the following patent claims. Seeking effect repair [Simplified schematic diagram] Figure 1 is a schematic diagram of the structure of a conventional flexible circuit board. FIG. 2 is a preferred embodiment of a flexible circuit board of the present invention.
【主要元件符號說明】 [習知] 軟性電路板 差分傳輸線 50 52、54 差分對 51 [本發明] 訊號層 10 差分對 11 差分傳輸線 12、η 接地銅箔 16 絕緣介質 20 接地層 30 200948234 32 挖空區域[Major component symbol description] [Practical] Flexible circuit board differential transmission line 50 52, 54 differential pair 51 [Invention] Signal layer 10 differential pair 11 differential transmission line 12, η ground copper foil 16 insulating medium 20 ground layer 30 200948234 32 Empty area
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