AP210 Recommended practises

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1 NOTICE:
2 bug numbers
3 Edition 2 specific recommendations
4 Edition 1 specific recommendations

NOTICE:

This page is under construction and contains both Edition 1 and Edition 2 version of the documents. Edition 1 sections will be incrementally replaced with equivalent Edition 2 sections. The first place to look for guidance on queries is Image:NIST-AP210Task4Deliverables-5-31-07-Stori.zip

bug numbers

Some items refer to bug numbers on the AP210 issue tracking site. http://step.nasa.gov/sparkynet/bugs. Relevant content will be moved to this site as time permits.

Edition 2 specific recommendations

pastemask layers. (bug 1164)

PWA/PWB layout systems include multiple layers that are intended to support tool and process development. Currently available translators from CAD to AP210 for PWA/PWB layout retain pastemask layers attached to the PWB definition and may cause confusion in receivers if they are mistakenly interpreted as part of the PWB material stackup. Current receiver implementations shall take this condition into account and shall not consider the explicit location of the pastemask layer in the stratum sequence to be relevant but shall rely on the domain knowledge that precedence is metal, soldermask, silkscreen, paste. One or more items in the sequence may be absent. In future versions of the translators, the pastemask layer mappings will be replaced with relevant information at the PWA definition.

Some options being considered for publication in 2007 edition

It has been proposed that pastemask layer when combined with additional information may be used to define a paste stencil tool. It has been proposed that the paste layer or the inverse of the pastemask layer be used to define the shape of the bond agent for the Application Object (AO) Assembly_bond_definition and to place that bond agent shape in the footprint definition. This is beneficial since it retains the single source definition model in the footprint definition and yet allows a split between the PWB and the PWA models. This is the most likely scenario to be implemented, since Assembly_joint is currently implemented and the change would be relatively minor. It has been proposed to remove the predefined layers that are not relevant to PWB definition since that is the root cause of the problem.