精密PCB製造、高頻PCB、高速PCB、標準PCB、多層PCB和PCB組裝。
1 如何選擇 PCB電路板
選擇 PCB板 必須在滿足設計要求和批量生產性及成本之間取得平衡. 設計要求包括電力和機械部件. 通常在設計超高速時 PCB板s (frequency greater than GHz) this 材料 problem will be more important. 例如, 常用FR-4.資料, 幾個GHz頻率下的介電損耗將對訊號衰减產生很大影響, 可能不合適. 就電力而言, attention should be paid to whether the dielectric constant (dielectric constant) and the dielectric loss are suitable for the designed frequency.
2. How to avoid high frequency interference
The basic idea of avoiding high-frequency interference is to minimize the interference of the electromagnetic field of high-frequency signals, which is the so-called crosstalk (Crosstalk). 您可以新增高速訊號和類比信號之間的距離, 或添加地面防護/類比信號旁邊的分路記錄道. 還要注意從數位接地到類比接地的雜訊干擾.
3. 在高速設計中, how to solve the problem of signal integrity
Signal integrity is basically a matter of impedance matching. 影響阻抗匹配的因素包括信號源的結構和輸出阻抗, 軌跡的特徵阻抗, 負載端的特性, 軌跡的拓撲結構. The solution is to rely on termination (termination) and adjust the topology of the trace.
4. How is differential wiring implemented
There are two points to pay attention to in the wiring of the differential pair, 一是兩條線的長度應該盡可能長, and the other is that the distance between the two lines (this distance is determined by the differential impedance) should always remain unchanged, 那就是, 它應該保持平行. 有兩種平行的管道, one is for two lines to run on the same wiring layer (side-by-side), and the other is for two lines to run on two adjacent layers (over-under). 通常地, 有很多方法可以同時實現前者. î
5. 對於只有一個輸出的時鐘訊號線, how to implement differential wiring
To use differential wiring, 只有信號源和接收端都是差分訊號才有意義. 因此, 差分路由不能用於只有一個輸出的時鐘訊號.
6. Can a matching resistor be added between the differential line pairs at the receiving end
The matching resistance between the differential line pairs at the receiving end is usually added, 其值應等於差分阻抗的值. 這將使訊號質量更好.
7. Why should the wiring of the differential pair be close and parallel
The differential pairs should be routed appropriately close and parallel. The so-called appropriate proximity is because this spacing will affect the value of the differential impedance (differential impedance), 這是設計差分對的一個重要參數. 為了保持差分阻抗的一致性，還需要並行性. 如果兩條線突然遠近, 差動阻抗將不一致, which will affect the signal integrity (signal integrity) and time delay (timing delay).
8. How to deal with some theoretical conflicts in actual wiring
1) Basically, 隔離類比電路是正確的/數位地面. It should be noted that the signal traces should not cross the divided places (moat) as much as possible, and do not let the return current path of the power supply and the signal (returning current path) become too large. î
2) The crystal oscillator is an analog positive feedback oscillation circuit. 要有穩定的振盪訊號, 它必須滿足環路增益和相位的規格, 這種類比信號的振盪特性很容易受到干擾. 即使添加了地面防護痕迹, 干擾可能無法完全隔離. . 太遠了, 接地層上的雜訊也會影響正回饋振盪器電路. 因此, 晶體振盪器和晶片之間的距離必須盡可能近.
3) Indeed, 高速佈線和電磁干擾要求之間存在許多衝突. 然而, 基本原理是，由於電阻，訊號的某些電力特性無法滿足規範要求, EMI添加的電容或鐵氧體磁珠. 因此, 首先使用排列軌跡和PCB堆疊的技巧來解决或减少EMI問題, 例如通過內層的高速訊號. 僅使用電阻-電容器或鐵氧體磁珠方法來减少對訊號的損壞.
9. How to solve the contradiction between manual wiring and automatic wiring of high-speed signals
Most of the automatic routers of strong routing software now have set constraints to control the routing method and the number of vias. 不同EDA公司的繞線機能力和約束設定項目有時非常不同. 例如, 是否有足够的約束來控制蛇蜿蜒的管道, 是否控制差分對的軌跡間距, 等. 這將影響自動佈線方法是否符合設計師的想法. 此外, 手動調整接線的困難也與繞線機的能力有關. 例如, 軌跡的推進能力, 通孔的推動能力, 甚至微量元素對銅塗層的推動能力, 等. 因此, 選擇具有强大繞線引擎能力的路由器是解決方案.
10. About the test coupon
The test coupon is used to measure whether the characteristic impedance of the produced PCB板 meets the design requirements by TDR (Time Domain Reflectometer). 通常地, 要控制的阻抗有兩種情况：單線和差分對. 因此, the line width and line spacing (when there is a differential pair) on the test coupler should be the same as the line to be controlled. 重要的是量測時接地點的位置. 為了降低接地線的電感值, TDR探頭的接地位置通常非常靠近探頭尖端. 匹配上使用的探針 PCB板.
