Rigid Flex Checks

Introduction

The Rigid Flex Checks is designed to analyze the flex layer/part of rigid flex board, similar to Flex board checks, it include the following tests: bend area, air gap, Coverlay, EMI and flex signal part analysis. In additional this action will check the interface axis/area - rigid part connect flex part area, and the distance between flex part and rigid part. Rigid Flex Checks requires the special license option rflxanl .

Definitions

Interface Axis

The Interface area or axis defines the location where the rigid area touches the flex area. There are specific restrictions which apply to this area and therefore it is important to know where the interface area is located. The Interface area can be defined as the common edges in the flex/rigid zones.

  

Interface Area

The Interface area is usually defined by a single intersection between Rigid and Flex areas. However, the requirement is to define a specific area (similar to the bend area) when checking for line width changes, perpendicular lines, and direction changes.

The width of the interface area is defined by the smallest value of the following parameters:

  • interface to pth/via
  • interface to coverlay/SM
  • interface to air-gap

multiplied by 2.

For example: if Interface to pth/via = 3 mm, Interface to coverlay/SM = 4 mm and Interface to airgap = 5 mm, then width of the interface area will be 6 mm (3 mm on either side of the interface axis).

  • EMI, Bend area layer, Adhesive layer / air gap are same as Flex board check.

Silver Mask Layer (EMI)

The silver shield or EMI is a conductive coating which is added to the Flex PCB in specified areas as defined by the silver mask layer.

The analysis for Silver mask layer requires that one of the following conditions be met:

  • Areas where the silver mask should be applied are defined by closed outlines. These areas of the silver mask should be defined as layer type conductive_mask and context=board .
  • An empty layer defined as layer type conductive_mask and context=board , and a punch or rout layer ( context = board ) which has it's span defined on this silver mask layer.

Adhesive Layer

Adhesive is the material that is applied in between signal layers to glue multilayer boards together. Usually the designer will provide an outline where adhesive should be applied and where not. The locations within the board profile where no adhesive is applied are referred to as "air gaps". The main purpose of air gaps is to achieve better bendability of the multilayer flex in specific locations. If multilayers are bonded over the complete surface then the PCB may become too rigid. So, in places where more flexibility is required, there is usually no bonding, and the adhesive material is removed in those locations. The adhesive is usually removed by punching or routing the adhesive material in those places where the air gaps are located.



The analysis for adhesive/air gaps requires that one of the following conditions be met:

  • Areas where adhesive should be applied are defined by closed outlines. The adhesive layer should be defined as layer type psa and context=board .
  • An empty layer defined as layer type psa and context=board , and a punch or rout layer ( context=board ) which has it's span defined on this adhesive layer.

Bend Area Layer

Bend area defines parts of the board that will be (pre-) bent in order to fit the board in a specific assembly. The bend area should be defined as an outline or surface on a layer with type bend_area and context=board.

   

Stiffener Layer

Stiffener defines an area on the board that should be rigidized, either with FR4 or with adhesive stiffener material (e.g. 3M stiffeners). In the case of FR4, usually a separate stiffener step is created which will be panelized in a different panel. In such cases, the stiffener area will be defined as an area layer.

In other cases, the stiffener might be punched or routed in places where no stiffener is required. In these situations, a "negative" image will be created which defines the locations where no stiffener should be applied.

 

Stiffener analysis requires a layer of type stiffener that defines the boundary of the stiffener by a closed outline or surface.