Drift-sensitive laser trimming of circuit elements

Abstract

In the laser trimming of passive circuit elements such as resistors, capacitors and inductors, various trimming parameters must be selected. To select a parameter, such as a cut type or speed, a value of a parameter, such as the resistance or impedance of a resistor, of each of a plurality of elements is measured. The measured parameter value of each element is compared with a target value for the parameter to determine an offset value between the measured parameter value and the target value. The relevant trim parameters are then selected based on the determined offset values.

1 . A method for laser trimming a circuit element, comprising: 
 identifying parameters associated with the element, including at least one of a paste composition from which the element is formed and a subsequent manufacture processing step to which the element is subjected; and    selecting a trim parameter based the identified parameters to reduce subsequent drift in element value.    
   
   
       2 . The method of  claim 1  wherein the identified additional parameters further include a geometric parameter of the element.  
   
   
       3 . The method of  claim 1  wherein the identified additional parameters further include at least one of a forming method of the element, a type of substrate on which the element is disposed, substrate mounting material, and surrounding materials proximate the element.  
   
   
       4 . The method of  claim 1  wherein the trim parameter is at least one of a type of cut for trimming the element, laser wavelength, laser pulse energy, spot size, speed at which the cut is made, bite size of the trim, and laser beam repetition rate of emission.  
   
   
       5 . The method of  claim 1  wherein the subsequent manufacture processing step is at least one of lamination, curing, and drilling.  
   
   
       6 . The method of  claim 1  wherein the subsequent manufacture processing step is a lamination process that embeds the element into a work piece using a dielectric layer.  
   
   
       7 . The method of  claim 1  wherein the subsequent manufacture processing step is a lamination process that embeds the element into a work piece using a conductive layer.  
   
   
       8 . The method of  claim 1  wherein the subsequent manufacture processing step includes applying a layer of dielectric over at least a portion of the element.  
   
   
       9 . The method of  claim 1  wherein the subsequent manufacture processing step includes applying a conductive layer over at least a portion of the element.  
   
   
       10 . The method of  claim 1  wherein the subsequent manufacture processing step includes applying at least one of a dielectric layer and a conductive layer over at least a portion of the element, and applying heat to the element and the one or more layers.  
   
   
       11 . The method of  claim 1  wherein the element has an actual value that is outside its target range, the method further comprising: 
 trimming the element in accordance with the selected trim parameter to change the actual value to be within the target range.    
   
   
       12 . The method of  claim 11  wherein the target range is selected based on anticipated subsequent drift in element value associated with the identified parameters.  
   
   
       13 . A method for laser trimming a circuit element, comprising: 
 identifying parameters associated with the element that are substantial contributors to subsequent drift in element value, the identified parameters including at least one of a paste composition from which the element is formed, a subsequent manufacture processing step to which the element is subjected, a forming method of the element, a type of substrate on which the element is disposed, substrate mounting material, and surrounding materials proximate the element;    selecting a trim parameter based the identified parameters to reduce the subsequent drift in element value; and    trimming the element in accordance with the selected trim parameter.    
   
   
       14 . The method of  claim 13  further comprising: 
 determining an anticipated subsequent drift in element value based on the identified parameters;    wherein the element is trimmed to have a target value that is selected based on the anticipated subsequent drift.    
   
   
       15 . The method of  claim 13  wherein the trim parameter is at least one of a type of cut for trimming the element, laser wavelength, laser pulse energy, spot size, speed at which the cut is made, bite size of the trim, and laser beam repetition rate of emission.  
   
   
       16 . The method of  claim 13  wherein the subsequent manufacture processing step includes applying at least one of a dielectric layer and a conductive layer over at least a portion of the element, and applying heat to the element and the one or more layers.