Peter

Many many jears ago in the last century ( '97b) , when I was still young and TechNet smaller we discussed the same item ( sounds like one of them grandpa's with no teeth left). You find the conversation below. 
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Blow out of PHT solder joints is not only a question of the copper
thickness but also of the moisture contents of the board and, very
important, of the quality of the drilled hole. If the PCB manufacturer is
using the drills too long or if he's feeding too much while drilling (
price pressure ) you will find ripped out glass fibres causing hollow
sections as well as glass fibres reaching out of the drilled walls. Both
cause a porous copper plating of the holes no matter how thick the final
plating is especially because the first process step of plating, where the
walls of the holes are covered electroless with a layer of copper in order
to make galvanic plating possible, will not cover all these
irregularities. Give me your Fax number. I can send you a 3-D graph where
the average amount of voids in a solder joint vs. the average copper
thickness and the number of not metallized glass fibres after the
electroless copper plating is shown.


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Hi TechNet
>
>I got so many notes of people that are interested in the 3D graph I
>mentioned that I decided it might be the easiest ( for me ) to send the
>data to TechNet since I can't send a picture. Those who are interested can
>use the data to make their own graph with any data handling program. I
>there is still someone having problems please feel free to contact me
>again.
>
>1. Specimen preparation:
>Test boards where produced with drills of various age with various feeding
>and various final plating thickness ( electroless plus electrical ).
>
>2. Analysis:
>Of each drill-feeding rate combination some samples have been drawn after
>electroless plating. microsections of the holes where done without
>embedding the specimen in resin. With transmission illumination the opened
>holes where investigated. Not plates glass fibres where clearly visible as
>bright spots.
>The soldered specimen where investigated with microsections.
>
>This work was done approx. 4 years ago at Siemens.
>Due to the test set-up it is clear, that not all possible measurement
>points could be found.
>
>3. Graph
>- X Axis ( classes of final plating thickness )
>- Y Axis ( classes of average amount of not metallised fibres after
>electroless plating )
>- Z Axis ( average amount of voids in the solder )
>
>Data matrix as follows
>- Top horizontal row = X Axis
>- Left vertical row = Y Axis
>- centre data = Z Axis
>
>
>                      I 24-30 I 24-34 I 26-32 I 28-38 I 28-42 I 30-36 I 30-40
>----------------------I-----------I-----------I-----------I-----------I-----------I-----------I-----------I
>0                    I   8      I           I           I           I   4      I           I   1      I
>1-10               I  20     I           I           I           I           I           I           I
>11-30             I           I           I   30    I           I           I   80    I           I
>More than 30 I           I  172   I  165   I           I           I   95    I           I

―


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Best regards

Guenter




Guenter Grossmann

Swiss Federal Institute for Materials Testing and Research EMPA
Centre for Reliability
8600 Duebendorf
Switzerland

Phone: xx41 1 823 4279
Fax :      xx41 1823 4054
mail:     [log in to unmask]

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