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February 1997

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Tue, 4 Feb 1997 22:45:28 +0100
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Thomas,

   about the 1) question,like I write in my first mail, there is in my
   experience in production environments,the idea that the most hard
   to control misregistration problem is caused by "shrinkage" of laminates
   and it's very uniform in the same lay-up configuration.If the random 
   misregistration problems are of the same dimension of shrinkage than
   I can think that very big mechanical-registration problems exist and
   can be normally removed.

   about the 2) question,I can tell you that the system can compensate 
   the gerber files of outer_layers,solder_mask and jig drill files,but
   like I write in my second mail("misregistration test") I think it's
   necessary this action(to correct the outer layers) over +/-4 mils at
   the limits of the board in a typical european pcb project. 


  about the question derived from 2) (considering needed an outer layer
correction) I think that the problem can be the fine-pitch smt automatic
mounting.About this problem is under evaluation the implementation of an
  intelligent algorithm that can save the absolute position of smt only,
  but the most hard in this is the checking and saving of minimum spaces.     

  Best regards,

                                             Luca Marchese




> Luca,
>
>	 I was an NC Drill Operator for 5 years.   Correct me if I am
>wrong , but I understand that you are going to try to compensate for
>inner layer shrinkage by compensating the coordinates for the drilled
>holes,  resulting in holes drilled mid-pads spanning the board.   
>
>        I have a few problems you may encounter:
>
>	1)  Unless your multilayer press can process all the boards of a
>certain part 	      simultaneously,  your going to have to gather
>all the boards processed 	      in the same book.  Then do this
>kind of offset adjustment for each book, 	      respectively, 
>because every book will need a different compensation.
>
>	2)  You will have to compesate the outer layer artwork on both
>sides of the 	      panels from each book, respectively.  
>
>	3)  You will have to special order all of the compensated
>components 	      	     respective to their position in
>each board.
>
>	4)   You will have to set the component insertion machine to
>insert the 	      	       appropriate,  properly
>compensated components on the appropriate 	       compensated
>boards so that they can fit into the compensated holes, 	      
>(and do this for each panel processed in the same book, respectively).
>
>	5)   If you do this.....you will have a working circuit board.  
>Otherwise you will 	       have a lot of scrap for External
>Misregistration....quite possibly charged 	       to your
>Engineering Department.   Seems pretty costly either way
>
>
>		Let me know how you do.
>
>	Tom Belliveau
>	Drill Dept. Inspector
>	HADCO CORP.
>	Derry Division
>
>On Fri, 31 Jan 1997 22:59:11 +0100 [log in to unmask] writes:
>>I'm an italian engineer specialized on AI-software application to 
>>ml-PCB
>>manufactoring.
>>I would like to know the judgement of technical people on a system 
>>that I'm
>>developing/testing, and their experience.The system can detect a 
>>signal from
>>a CNC machine while it's drilling a particular small test-coupons on
>>ml-pcb(it's not important now ,how it can do it).
>>After it can calculate the innerlayer misregistration and correct
>>the all coordinates of the drilling file.
>>This correction can make a compensation to offset/rotation and
>>EXTENSION-SHRINKAGE.It can operate also with a Multiline 
>>registration-system
>>because it does'n create  new register holes but corrects the 
>>coordinates of
>>the file.In the production enviroments that I know, the big problem is 
>>not
>>the "RANDOM" MECHANICAL REGISTER DEFECT but the LAY-UP-DEPENDENT 
>>SYSTEMATIC
>>DIMENSIONAL INSTABILITY.So, for me is easy think that it is better  
>>make a
>>best correction of the all coordinates one time and apply to all 
>>boards than
>>make a new offset to register holes for any board.I think also that 
>>the last
>>methodology cannot have a better result than a Multiline register 
>>system when
>>the big problem is dimensional stability.For my experience is very 
>>hard the
>>modification of the film dimension to compensate the material 
>>dimensional
>>instability due to the dinamics of the suppling firm of lamites and 
>>organization
>>delay time in film production.
>>This is my think, and would like to know Your think about.
>>Thanks,
>>
>>                                                 Luca Marchese
>>                                                 
>>[log in to unmask]   
>>
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>

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