Data processing: structural design – modeling – simulation – and em – Modeling by mathematical expression
Reexamination Certificate
1999-03-15
2003-12-02
Broda, Samuel (Department: 2123)
Data processing: structural design, modeling, simulation, and em
Modeling by mathematical expression
C703S007000, C702S085000, C716S030000, C029S830000
Reexamination Certificate
active
06658375
ABSTRACT:
NOTICE REGARDING COPYRIGHT
A portion of the disclosure of this patent document contains matter subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent disclosure document as it appears in the Patent and Trademark Office files and records but otherwise retains all copyrights whatsoever.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to multilayer printed circuit boards and, more particularly, to registration of multilayer printed circuit boards (MLB) prior to lamination.
2. Description of Related Art
There are few problems as challenging or as important in the printed circuit board industry as registration. Examination of the MLB scrap pile at drill or electrical testing sites can be mysterious and aggravating. One circuit out of a lot or on a panel may be perfect and the next circuit may be a confusing pattern of errors. If the scrap amount is significant, then there is need for immediate circuit board design modifications. Often the modifications required to correct the registration problems are not apparent so that the modifications that are implemented often give unsatisfactory results.
Multilayer printed circuit board registration errors come from a variety of sources including: (1) offset error; (2) angle error; (3) random noise; (4) compensation error. Compensation errors arise from mistakes in estimating the shrinking or expanding of the MLB due to material movement experienced following multilayer lamination of the cores and dielectric.
Unfortunately, in estimating the required compensation, the prior art merely suggests considering the amount of copper on an individual core by image, and the thickness of the core with no regard to the overall multilayer board design and construction. The data used to generate the matrix in the prior art is based on historical production information. These prior art models fail to precisely estimate the required compensation, and at times, produce as much as a ±15 mil error between the model and the actual production. One example of a prior art compensation matrix is shown in FIG.
1
. The matrix is for 24″×18″ panels where the warp (X-direction) direction is 18″ and the fill (Y-direction) direction is 24″. The prior art matrix is based solely on the amount of copper on the core by image and the thickness of the core, dramatically limiting the usefulness in reducing compensation error.
In practice, use of the prior art compensation matrix disrupts the processing of multilayer printed circuit boards.
FIG. 2
shows a flow chart of a simplified process map for a compensation process for a large printed circuit board shop. Arrows
30
in
FIG. 2
indicate areas of the process that are very unstable. In a feedback process, which
FIG. 2
describes, adding the wrong information will cause small mistakes that create large registration errors. This occurs when the feedback information is wrong or the feedback happens after a long lag period. Unfortunately, the nature of printed circuit board shops with large amounts of work in process greatly limits the ability to remove the detrimental lag time. Incomplete information and delay of input also limits the ability to make compensation changes on the fly. Making compensation changes after full production lots have been released is nothing more than process tampering, which often leads to escalating scrap rates. One way to improve compensation error is by improving the accuracy of compensation predictions for a job prior to production. Prior art strategies based on historical production data sets lack the required design combinations to detect the important variables and interactions that control the material movement. Therefore, the prior art compensation matrices do not accurately predict the error prior to production, thereby requiring costly modifications during production.
At block
32
of
FIG. 2
, the initial compensation values are selected from the sizing matrix of FIG.
1
. At block
34
, the test books (which typically 10 or more MLBs stacked on top of one another) and first production lots are “released” (started) to production. Due to time pressures, it is typically not feasible to first run tests to determine whether there will be production problems (i.e., whether the predicted compensation values were, in fact, correct) and then run the actual production. Instead, the test books and the production lots must be prepared for production simultaneously. At block
36
, the test books are measured for errors and the production is run. Thereafter, at block
38
, the overages (which are additional cores that have layers etched on them) are collected in the core inventory. Because some of the printed circuit boards are expected to fail, overages of additional cores with layers are manufactured. These overages are stored in the event that they are needed.
At block
40
of
FIG. 2
, based on the measurements of the test books in block
42
, the artwork is changed in order to reduce compensation errors. However, due to old lots still being in the production pipeline, the old lots are still being used, as shown in block
44
, which cause an unstable lag in terms of correcting the problems in the production. And, due to time pressures, the old cores are still used in the production, as shown at block
46
.
The present methods of determining and correcting MLB registration errors are ineffective and unpredictable, resulting in large volumes of scrap. Thus, there remains a need to determine registration errors and in particular compensation error before production begins rather than during production.
In addition, the prior art fails to appreciate the interaction between the different sources of registration error. Typically, the prior art merely adds the variances which comprise the sources of registration error in an attempt to compute the total registration error. For example, compensation error from artwork, offset error and angle error from a post etch punch machine, and random noise from a drill machine cannot be combined by using the sum of the squares. However, this one-dimensional analysis does not provide insight on how the errors flow over the panel surface and how the sources of registration error are interdependent, combining to produce complex and seemingly unexplainable registration error patterns. There remains a need to account for the interaction of all types of errors in order to improve MLB registration.
SUMMARY OF THE INVENTION
In a first aspect of the invention, a method for modeling compensation during registration of a printed circuit board is provided. The method comprises the step of providing a plurality of printed circuit boards with multiple cores which use at least one dielectric layer in between the cores. The method also comprises the step of measuring the movement of least one core of each printed circuit board due to fabrication. And, the method comprises the step of generating a compensation model based on the core movement and based on the at least one dielectric layer.
In a second aspect of the invention, a method for modeling compensation during registration of a printed circuit board is provided. The method comprises the step of providing printed circuit boards with multiple cores with dielectric layers in between the cores, the cores having positions in the printed circuit boards. The method also comprises the step of measuring the movement of the cores due to fabrication of the printed circuit boards. And, the method comprises the step of generating a compensation model based on the core movement and based on the position of the cores in the printed circuit board.
In a third aspect of the invention, a method for modeling compensation during registration of a printed circuit board is provided. The method comprises the step of providing printed circuit boards having at least a first core and a second core, with circuit layouts on at least one side of the first core and on at least one side of the second core. The metho
Jones Bradley A.
McQuarrie W. Gray
Broda Samuel
Isola Laminate Systems, Inc.
McDonnell Boehnen Hulbert & Berghofff
LandOfFree
Compensation model and registration simulation apparatus and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Compensation model and registration simulation apparatus and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Compensation model and registration simulation apparatus and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3100721