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# How to form laser holes efficiently by changing a beam shot sequence (Scatter shot method)

IP.com Disclosure Number: IPCOM000011951D
Original Publication Date: 2003-Mar-27
Included in the Prior Art Database: 2003-Mar-27
Document File: 1 page(s) / 16K

IBM

## Abstract

Disclosed is a method for forming vias and through holes in printed circuit board by laser drilling. As through hole pitch becomes small and laser speed increases, the laser heat energy for a through hole tends to spread and reaches the position of adjacent through hole so that the adjacent through holes are to be drilled under unstable heat condition and have a large distribution of geometry in them. This invention discloser provides a method to control the heat condition by optimizing the laser drilling sequence.

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THIS COPY WAS MADE FROM AN INTERNAL IBM DOCUMENT AND NOT FROM THE PUBLISHED BOOK

JP820021238 Fumio Koike/Japan/IBM Masaharu Yasuda, Yutaka Tsukada

How to form laser holes efficiently by changing a beam shot sequence (Scatter shot method)

Figure 1 shows a typical example of conventional drilling sequence which is  determined to minimize the total moving distance among through hole positions.  Through holes are formed in the order as follow.

(X1, Y1)-> (X2, Y2)-> (X3, Y3)-> (X4, Y4)-> (X5, Y5)

When hole at (X1, Y1) is processed, the temperature at (X2, Y2) tends to  rise by the laser heat from position (X1,Y2). When laser speed is fast  enough, the through hole at (X2,Y2) will be processed in a higher  temperature condition. As laser speed increases and pitch of through hole  becomes small, the temperature at (X2,Y2) is not likely under control. One  of solutions is "adding a waiting time before going to the next position  for cooling", which results a longer process time. This invention discloser provides the method which avoids a longer process  time by changing the sequence of laser drilling positions and sets the  temperature condition in control. Figure 2 shows an...