Adaptive threshold determination for ball grid array component modeling
View Patent ↗A method for determining a number of balls in a projection space comprises determining a projection of a portion of a ball grid array, determining at least one local maximum of the projection space for a given threshold, and determining at least a distance between adjacent maximum. The method further comprises determining an inter-peak histogram of the distances, determining an inter-ball distance for each pair of adjacent balls that has the maximum value of the inter-peak distance histogram corresponding to the pair of adjacent balls, and determining a position of a first ball and a position of a last ball. The method comprises verifying the position of the first ball and the position of the last ball based on a general inter-ball distance, and determining the number of balls.
1. A method for determining a number of balls in a projection space comprising the steps of:
determining a projection of a portion of a ball grid array;
determining at least one local maximum of the projection space for a given threshold;
determining a distance between adjacent maximum;
determining an inter-peak histogram of the distances;
determining an inter-ball distance for each pair of adjacent balls that has the maximum value of the inter-peak distance histogram corresponding to the pair of adjacent balls;
determining a position of a first ball and a position of a last ball;
verifying the position of the first ball and the position of the last ball based on a general inter-ball distance; and
determining the number of balls.
2. The method of claim 1 , wherein the step of determining the projection further comprises the step of projecting a row or column of an image of the balls in a direction, wherein the direction is one of horizontal and vertical.
3. The method of claim 1 , wherein an inter-peak distance bin width is a tolerance of the general inter-ball distance.
4. The method of claim 1 , wherein the number of balls is determined according to:
N
=
distance
between
the
first
and
the
last
ball
inter
-
ball
distance
+
1
where N is the number of balls and the inter-ball distance is determined according to a maximum value of the inter-peak distance histogram.
5. The method of claim 1 , wherein the given threshold is an adaptive threshold.
6. The method of claim 5 , further comprising determining the adaptive threshold, comprising the steps of:
determining a preliminary number of balls in the projection space for one or more threshold values in a threshold searching range based on the general inter-ball distance of ball grid array components;
determining a histogram for the preliminary number of balls;
determining a threshold range comprising a plurality of threshold values, wherein each threshold value corresponds to a maximum number of balls at the threshold value; and
setting the adaptive threshold to one of a mean threshold value and a median threshold value of the threshold range.
7. The method of claim 6 , wherein the histogram shows a maximum frequency of the number of balls.
8. The method of claim 1 , wherein the general inter-ball distance is an average of the distances between each pair of adjacent balls.
9. A program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform method steps for determining a number of balls in a projection space, the method steps comprising:
determining a projection of a portion of a ball grid array;
determining at least one local maximum of the projection space for a given threshold;
determining a distance between adjacent maximum;
determining an inter-peak histogram of the distances;
determining an inter-ball distance for each pair of adjacent balls that has the maximum value of the inter-peak distance histogram corresponding to the pair of adjacent balls;
determining a position of a first ball and a position of a last ball;
verifying the position of the first ball and the position of the last ball based on a general inter-ball distance; and
determining the number of balls.
10. The method of claim 9 , wherein the step of determining the projection further comprises the step of projecting a row or column of an image of the balls in a direction, wherein the direction is one of horizontal and vertical.
11. The method of claim 9 , wherein an inter-peak distance bin width is a tolerance of the general inter-ball distance.
12. The method of claim 9 , wherein the number of balls is determined according to:
N
=
distance
between
the
first
and
the
last
ball
inter
-
ball
distance
+
1
where N is the number of balls and the inter-ball distance is determined according to a maximum value of the inter-peak distance histogram.
13. The method of claim 9 , wherein the given threshold is an adaptive threshold.
14. The method of claim 13 , further comprising determining the adaptive threshold, comprising the steps of:
determining a preliminary number of balls in the projection space for one or more threshold values in a threshold searching range based on the general inter-ball distance of ball grid array components;
determining a histogram for the preliminary number of balls;
determining a threshold range comprising a plurality of threshold values, wherein each threshold value corresponds to a maximum number of balls at the threshold value; and
setting the adaptive threshold to one of a mean threshold value and a median threshold value of the threshold range.
15. The method of claim 14 , wherein the histogram shows a maximum frequency of the number of balls.
16. The method of claim 9 , wherein the general inter-ball distance is an average of the distances between each pair of adjacent balls.