# US 4,400,618 A · Method of detecting and analyzing damage in printed circuit boards

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- Number: US 4,400,618 A
- Document ID: US4400618A
- Status: Granted
- Kind: A
- Application number: 06/290,632
- Filed: 1981-08-06
- Granted: 1983-08-23
- Earliest claimed: 1981-08-06
- Assignees: International Business Machines Corporation
- Inventors: James R. Bupp; Lawrence R. Maier
- Web page: https://patentgrep.com/patent/US4400618A

## CPC

- G01N 21/91: using penetration of dyes, e.g. fluorescent ink
- H05K 1/0269: {for visual or optical inspection}
- H05K 3/0052: {Depaneling, i.e. dividing a panel into circuit boards; Working of the edges of circuit boards}
- H05K 3/0055: {After-treatment, e.g. cleaning or desmearing of holes}
- H05K 2203/0228: Cutting, sawing, milling or shearing
- H05K 2203/161: Using chemical substances, e.g. colored or fluorescent, for facilitating optical or visual inspection
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS

## Abstract

A method of detecting flaws in a printed circuit board laminate having drilled holes wherein a penetrating solution containing a UV fluorescing dye is applied to the laminate to fill the drilled holes and flaws. Excess penetrating solution is removed from the drilled holes and the surface of the laminate. The penetrating solution remaining in the flaws is cured into an insoluble solid and then the laminate is cross-sectioned to provide at least one sample carrying the cured solution. The sample is encapsulated in a clear epoxy and the encapsulated sample is ground and polished to provide a surface which is examined under UV light.

## Claims

### Claim 1

A method of detecting flaws in a printed circuit board laminate having drilled holes comprising:
applying a penetrating solution containing multifunctional methylacrylates and a UV fluorescing dye to said circuit board laminate to fill drilled holes and flaws therein, said penetrating solution being capable of being polymerized;
removing excess penetrating solution from the drilled holes and the surface of said circuit board laminate;
curing the penetrating solution remaining in the flaws into an insoluble solid;
cross-sectioning the circuit board laminate to provide at least one sample carrying the cured solution;
encapsulating the sample in a clear epoxy;
grinding and polishing said encapsulated sample to provide a surface to be examined; and
examining said surface under UV light.

### Claim 2 (depends on 1)

The method of claim 1 wherein the penetrating solution is stable in the presence of oxygen and is polymerizable in the absence of oxygen.

### Claim 3 (depends on 1)

The method of claim 1 wherein said surface to be examined is photographed under UV light to make a record showing the nature and location of the flaws.

### Claim 4

A method of detecting and analyzing flaws in a printed circuit board laminate having metallized circuit lines and lands and drilled holes comprising:
applying a penetrating solution containing multifunctional methylacrylates and a UV fluorescing dye to said circuit board laminate to fill drilled holes and flaws therein, said penetrating solution being capable of being polymerized;
removing excess penetrating solution from the drilled holes and the surface of said circuit board laminate;
curing the penetrating solution remaining in the flaws into an insoluble solid;
cross-sectioning the circuit board laminate to provide at least one sample carrying the cured solution;
encapsulating the sample in a clear epoxy;
grinding and polishing said encapsulated sample to provide a surface to be examined;
examining said surface under UV light; and
photographing said surface to be examined under both UV light and regular light to make a record showing the nature and location of the flaws which fluoresce and also the metallized circuit lines and lands which do not fluoresce.

### Claim 5 (depends on 4)

The method of claim 4 wherein said penetrating solution contains, in percentage by weight, about 70% of an anaerobic monomer, about 25% of a diluent, about 2% of an initiator, about 1% of an inhibitor, and about 2% total of a fluorescing dye, a nonionic surfactant, and an accelerator.

### Claim 6 (depends on 4)

The method of claim 4 wherein said penetrating solution contains, in percentage by weight, about 70% of triethylene glycol dimethacrylate, about 25% of lauryl methacrylate, about 2% of cumene hydroperoxide, about 1% of benzoquinone, and about 2% total of yellow "G" dye, "Poly-Tergent" B-300, and copper octanoate.