Richard,

Polyimide is very susceptible to  haloing especially around non plated holes that are drilled in a 2nd stage operation. Sometimes you will see the halo extend as much as .100-.150 out from the hole. The best solution for this is to drill the 2nd stage hole before you etch the panel. The copper cladding will generally eliminate any significant haloing. This is depending of course that your speeds and feeds are correct and you not "punching" out the holes.

Hope this helps.

Ed Cosper
Director Quality Assurance and Engineering.
Graphic Electronics, Inc.
Tulsa, OK 

----------
From:  Richard MacCutcheon[SMTP:[log in to unmask]]
Sent:  Tuesday, January 13, 1998 9:37 AM
To:  [log in to unmask]
Subject:  [TN] Haloing

======== Original Message ========
Two questions:

1. How much haloing on board edges and around non-plated holes is normally
encountered on polyimide type boards?

2. How much board or non-plated hole edge to conductor spacing is normally
required on polyimide boards to ensure that bridging of a halo does not
exceed 50% of the distance?

Assume 0.062 thick boards for each question.

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======== Fwd by: Richard MacCu ========
We encounter virtually no haloing on polyimide material.  All we run is GI
laminate.
We drill nonplated holes prior to etch of outers or after electroless
copper.
Typical feeds and speeds for dias. .122-.161 F04S20
                                                        .162-.250 F02S15
Routing panels we use .093 chipbreaker at 15K rpm with table feed of 30ipm.

These may seem slow but they produce excellent finish.
Hope this helps.

Richard MacCutcheon
BFGoodrich Aerospace

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