BGA Tie Line Generation

The BGA Tie Line Generation action generates the tie lines (and arcs) for BGA boards. These are the lines that connect each net of the board to the plating bars around the profile of the board, allowing the nets to be electro-plated with gold.

Calculate and Consider Board Nets

You may calculate and consider board nets in this action. A board net is a net that calculated on the 3 dimensions of the board through the board layers.

 The following images show part of the top layer of boards before and after the activation of this function.

 

Notes

The BGA Tie Line Generation action presumes that the profile of the board is the target of the action, i.e., the action connects the nets to the profile of the board. (Actually, the target is a little beyond or before the profile, depending on the value of the Profile Extension parameter.) This means that, as a prerequisite of this action, a profile must be correctly defined for the board.

A current limitation of the action is that the target profile is rectangular. If the actual profile of the board is not rectangular, than its bounding box is used.

An important piece of information to the action is the center of the BGA chip. The algorithm is much faster and produces better results if the center of the BGA is known to it. Usually, the BGA center can be taken as the center of the profile. The BGA Center parameter allows one to enter explicit coordinates for the center if this is not the case.

At the moment, the BGA Tie Line Generation action does not include a recognition process to identify the plating bars. If plating bars are present, the action will treat them as just another net. This means that if the plating bars are present, they need to be temporarily removed from the board for the action to work correctly.

Unlike most DFM actions, the BGA Tie Line Generation action operates on nets and not features. This means that:

*     The action generates a single set of tie lines and arcs for each net.

*     The success or failure of the tie line generation is determined on a per net basis.

*     The reports are on a per net basis.

A net will be considered as selected if any feature on the net is selected.

The BGA Tie Line Generation action tries to add tie lines to the nets of the side indicated by the Primary Side parameter . If the action fails to generate tie lines for a particular net on the primary side, the operator can control whether to try to generate tie lines for the secondary side (the other side of the board). This is done by setting the On Failure Try Secondary Side parameter to Yes . The determination of what is the corresponding net on the secondary side is simplistic but adequate for most BGA boards.

The action groups the failures into two groups in order to help the operator take the appropriate corrective actions.

Parameter Failures

These are failures in which the net cannot be tied to the profile even if it were the only net on which the action were to operate. The most common reason for this is that the line width and spacing parameters are too large to allow this net to be tied, but it may also be that the path of the tie lines is too complex.

Algorithm Failures

These failures happen when the net can be tied to the profile if it were the only net being tied, but tie lines belonging to other nets prevent this from happening.

When the On Failure Try Secondary Side parameter is set to Yes , the action may fail for a particular net on both sides of the board. In this case, the failure is grouped according to the type of failure on the secondary side of the board.

The generated tie lines and arcs have the .tie attribute set.

 

Special Reports

The first part of the report gives the number of tied nets, the number of outside profile nets, the number of parameters and the number of algorithm failures.

When running the action with the parameter On Failure Try Secondary Side set to Yes , these numbers are also broken down with respect to the two sides as follows:

*     The number of tied nets and the number of outside profile nets are given for the primary and secondary side.

*     The number of parameters and the number of algorithm failures are broken down into...

-         The number of failures which occur on the primary side only (these cannot be tried on the secondary side), and

-         The number of nets that fail first on the primary side and then on the secondary side
(these are classified as the type of failure on the secondary side).

The second part of the report is a count and histogram of the tie lines and arcs.

Result Attributes

Result attributes according to the following syntax are produced:

Attribute

Description

...tied

The number of tied nets

...outside

The number of outside profile nets

failed_param

The number of parameter failures

failed_alg

The number of algorithm failures

When running with the On Failure Try Secondary Side parameter set to Yes, the above refer to the numbers on both sides of the board.
In addition, the following result attributes will be created showing the breakdown of these numbers with respect to the two sides.

Attribute

Description

...tied

The number of tied nets on each layer

...outside

The number of outside profile nets on each layer

<primary_layer>_failed_param

The number of parameter failures on the primary side which could not be tried on the secondary side

<secondary_layer>_failed_param

The number of nets which fail on both sides, where the failure on the secondary side is a parameter failure

<primary_layer>_failed_alg

The number of algorithm failures on the primary side which could not be tried on the secondary side

<secondary_layer>_failed_alg

The number of nets which fail on both sides, where the failure on the secondary side is an algorithm failure