Backdrill相关设置及Backdrill文档输出方法_技术

Backdrill相关设置及Backdrill文档输出方法

如果PCB的层数超过4层，PCB的走线从其中的某两层走线（除从表层到表层外），总会产生类似于下图这种情形的stub：产生多余的镀铜部分，当电路信号的频率增加到一定高度后，多余的镀铜就相当于天线一样，产生信号辐射对周围的其他信号造成干扰，严重时将影响到线路系统的正常工作，Backdrill的作用就是将多余的镀铜用钻孔的方式钻掉，从而消除此类EMI问题。其 *** 作步骤和注意事项如下：

1.给net设定Backdrill_max_pth_stub属性

Property

BACKDRILL_MAX_PTH_STUB

Purpose

IdenTIficaTIon of nets targeted for backdrilling

Usage

Required

Value

Max allowable stub in length (database units)

Objects

Nets

Backdrill analysis flag

2.给net设定Backdrill_min_pin_pth属性， Backdrill_min_pin_pth 考虑可靠性, 必须保证BACKDRILL去掉多余镀铜后, 保证一定剩余一定长度.

Property

BACKDRILL_MIN_PIN_PTH

Purpose

Ensures minimum pin plaTIng depth is not compromised

Usage

OpTIonal

Value

Length

Objects

Symbols, pins

Backdrill analysis flag

3.压接的接插件backdrill：要保证良好的接触, 必须保证下面的值：

Property

BACKDRILL_PRESSFIT_CONNECTOR

Purpose

Use on pressfit connectors to permit backdrilling from both sides of the board. Backdrill depth will not protrude into contact range as defined by the property string.

Usage

Optional

Value

where values = pin contact range; this value must be obtained from the manufacturer

Objects

Symbols

Backdrill analysis flag

n/a

4.有些场合不能用此功能的可以用下面的命令排除.

Exclusions

It may be necessary to exclude certain objects from backdrilling even though stub violations are present. The BACKDRILL_EXCLUDE property can be applied to symbols, pins or vias at both the library and design level using Edit - Property. Common examples might include solder tail connectors or a dense pin escape pattern in BGA areas. The PCB designer should consult with a manufacturing engineer before assuming all pin/via objects are suitable for backdrilling.

Property

BACKDRILL_EXCLUDE

Purpose

Excludes objects from backdrilling even though stub may be present

Usage

Optional

Value

Boolean (true/false)

Objects

Symbols, pins, vias

Backdrill analysis flag

5.定义层（可选）

User Overrides

In most cases, the backdrill layer ranges defined in the Backdrill Setup and Analysis user interface satisfy your requirements to manage stubs. The BACKDRILL_OVERRIDE property allows user-specified control of layer ranges for any pin or via and from ether side of the board or both. This is done regardless of violations that may result, such as testpoint conflicts or backdrilling through a connection. The override property was considered for the design of test coupons where the OEM wishes to evaluate the performance of the board fabricator with respect to the adherence of depth ranges. The designer may override the "to" layer to effectively drill out the layer where the trace connects the pin/via. The expected usage of this property is limited; please exercise caution to prevent accidental over-drilling.

Property

BACKDRILL_OVERRIDE

Purpose

User-specified backdrill range

Usage

Optional: special circumstances

Value

TOP::BOTTOM:

Objects

Pins, Vias

Backdrill analysis flag

O or W (warning)