Multilayer type printed-wiring board and method of measuring impedance of multilayer type printed-wiring board

Abstract

The impedance of a newly manufactured data transmission wire pattern can be measured easily and accurately. A multilayer type printed-wiring board 1 comprises a pair of data transmission wire patterns 4, 5 arranged between a CPU module 2 and a memory module 3 on respective inner layer substrates 6, 7, impedance measuring wire patterns 21 and 22 arranged respectively in the layers same as those of the data transmission wire patterns 4, 5, a prepreg layer 11 arranged on the impedance measuring wire patterns 21, 22, land sections 23, 23 for signals arranged on the prepreg layer 11 and electrically connected to the impedance measuring wire patterns 21, 22 so as to be brought into contact with the signal terminal 41 of a probe 40 and a GND land section 24 also arranged on the prepreg layer 11 and electrically connected to the impedance measuring wire patterns 21, 22 so as to be brought into contact with the GND terminal 42 of the probe 40, the impedance measuring wire patterns 21, 22 having a pattern length not smaller than 30 mm that is the minimal length required for use with a TDR unit and a pattern width same as that of the data transmission wire patterns 4, 5.

1 . A multilayer type printed-wiring board comprising; 
 a first insulating layer;    a data transmission wire pattern arranged on said first insulating layer and adapted to data transmission between a CPU module and a main memory module to be used for the CPU;    an impedance measuring wire pattern arranged on said first insulating layer in the layer same as that of said data transmission wire pattern with a predetermined clearance to any adjacent wiring pattern;    a second insulating layer arranged on said data transmission wire pattern and said impedance measuring wire pattern; and    land sections for signals arranged on said second insulating layer and electrically connected to said impedance measuring wire pattern arranged on said first insulating layer by way of a through hole so as to be held in contact with the signal terminal of the probe for measuring the impedance of said impedance measuring wire pattern and a GND (grounding) land section held in contact with the GND terminal of said probe;    said impedance measuring wire pattern having a pattern length not smaller than about 30 mm and a pattern width same as that of said data transmission wire pattern.    
   
   
       2 . The multilayer type printed-wiring board according to  claim 1 , wherein the transmission frequency of said data transmission wire pattern is not less than 130 MHz.  
   
   
       3 . The multilayer type printed-wiring board according to  claim 1 , wherein the clearance between said impedance measuring wire pattern and any adjacent wiring pattern is not less than twice of the pattern width of said impedance measuring wire pattern.  
   
   
       4 . The multilayer type printed-wiring board according to  claim 1 , wherein the wiring pattern arranged around the impedance measuring wire pattern is a GND pattern connected to said GND land section by way of a plurality of through holes.  
   
   
       5 . The multilayer type printed-wiring board according to  claim 1 , wherein a plurality of impedance measuring wire patterns are arranged in different layers and electrically connected to each other by way of through holes.  
   
   
       6 . A method of measuring the impedance of a multilayer type printed-wiring board comprising: 
 a first insulating layer;    a data transmission wire pattern arranged on said first insulating layer and adapted to data transmission between a CPU module and a main memory module to be used for the CPU;    an impedance measuring wire pattern arranged on said first insulating layer in the layer same as that of said data transmission wire pattern with a predetermined clearance to any adjacent wiring pattern;    a second insulating layer arranged on said data transmission wire pattern and said impedance measuring wire pattern;    land sections for signals arranged on said second insulating layer and electrically connected to said impedance measuring wire pattern arranged on said first insulating layer by way of a through hole so as to be held in contact with the signal terminal of the probe for measuring the impedance of said impedance measuring wire pattern and a GND (grounding) land section held in contact with the GND terminal of said probe; and    said impedance measuring wire pattern having a pattern length not smaller than about 30 mm and a pattern width same as that of said data transmission wire pattern;    said method comprising a step of:    measuring the impedance of said impedance measuring wire pattern by bringing the signal terminal and the GND terminal of said probe into contact respectively with said land sections for signal and said GND land section.    
   
   
       7 . The method of measuring the impedance of a multilayer type printed-wiring board according to  claim 6 , wherein the transmission frequency of said data transmission wire pattern is not less than 130 MHz.  
   
   
       8 . The method of measuring the impedance of a multilayer type printed-wiring board according to  claim 6 , wherein the clearance between said impedance measuring wire pattern and any adjacent wiring pattern is not less than twice of the pattern width of said impedance measuring wire pattern.  
   
   
       9 . The method of measuring the impedance of a multilayer type printed-wiring board according to  claim 6 , wherein the wiring pattern arranged around the impedance measuring wire pattern is a GND pattern connected to said GND land section by way of a plurality of through holes.  
   
   
       10 . The method of measuring the impedance of a multilayer type printed-wiring board according to  claim 6 , wherein a plurality of impedance measuring wire patterns are arranged in different layers and electrically connected to each other by way of through holes.  
   
   
       11 . The method of measuring the impedance of a multilayer type printed-wiring board according to  claim 10 , wherein the impedances of said wiring patterns arranged in different layers are measured by measuring said plurality of impedance measuring patterns arranged in different layers in a single measuring operation.