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| Interposer and methods for fabricating same |
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| Energy beam patterning of protective layers for semiconductor devices |
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Method for photographically improving the resolution of screen printed photopolymer images
| Details |
Inventors: Sullivan, Donald F.;
Assignee:
Primary Examiner:
Assistant Examiner:
Attorney, Agent or Firm:
A process is described for improving the quality of images which have been formed by screen printing a liquid photo curable photopolymer. Images formed by screen printing, especially heavy coatings such as solder masks on printed wiring boards, inherently have indistinct boundaries, and may have feathered edges and photopolymer smears. These indistinct boundaries are removed and the resolution improved by a process which utilizes the oxygen inhibition effect characteristic of selected photopolymers. Thus, a screen printed image can be 0.001 inches thick at the center of a line, tapering off to 0.0001 inch thick smears, and these smears may be eliminated by irradiating the entire image with a moderate amount light energy, which cures the thick image portion and leaves a liquid boundary layer on the order of 0.0001 inch thick due to the oxygen effect. When washed with a mild solvent the liquid layer is removed, including the smears, leaving the thick image portion undisturbed. In a preferred embodiment a phototransparency is interposed over and out of contact with the images and then irradiated with non-collimated UV light so as to harden the thicker image sections while indistinct boundary areas are shielded by opaque phototransparency areas. Light undercutting due to the use of non-collimated light does not polymerize the smears because of the oxygen-inhibition effect and the thinness of the smears, and thus only the undersirable smears will be inhibited and left in the liquid state for removal to improve the resolution. |
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DETAILED DESCRIPTION I claim: 1.
The process of improving resolution of printed photopolymer patterns of low resolution because of smears at the pattern edges, comprising the steps of: printing on a substrate surface a pattern of photopolymer with an oxygen inhibited characteristic that leaves the surface in liquid form to a predetermined depth when photoexposed in the presence of air with a predetermined amount of radiation energy, wherein the printing leaves a low resolution pattern with smears of substantially reduced thickness from that of the polymer thickness of the pattern appearing at edge portions of the pattern, photoexposing the polymer pattern with the surface in contact with air to radiation of such energy that the smears are left in liquid form while polymerizing at least a substantial thickness of the polymer defining the pattern to adhere to the substrate and resist solvency to a predetermined solvent that will remove the liquid form smears of the polymer, and removing the liquid form smears with said solvent in a development step thereby to increase the resolution of the remaining polymerized pattern.
2.
The process defined in claim 1 including the further steps of: photoexposing the entire pattern and smear surface with said photoexposing step to leave the surface of the pattern in liquid form to said predetermined depth, and removing the liquid polymer from the pattern surface with the development step removing the smears.
3.
The process defined in claim 1 including the further step of: photoexposing the polymer pattern in said photoexposing step through a phototransparency separated from the polymer pattern by an air gap and registering a desired photopattern over the screen printed pattern having smear areas blocked from radiation by opaque portions of the phototransparency with sufficient radiation energy to polymerize the desired pattern throughout the depth of the polymer while leaving smears at the edges of the desired pattern in liquid form for removal in the development step
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MEMS 
