GB2081515A - Method of making printed circuit boards - Google Patents

Method of making printed circuit boards Download PDF

Info

Publication number
GB2081515A
GB2081515A GB8117990A GB8117990A GB2081515A GB 2081515 A GB2081515 A GB 2081515A GB 8117990 A GB8117990 A GB 8117990A GB 8117990 A GB8117990 A GB 8117990A GB 2081515 A GB2081515 A GB 2081515A
Authority
GB
United Kingdom
Prior art keywords
board
aperture
plating
electrically conducting
solder
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB8117990A
Other versions
GB2081515B (en
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nevin Electric Ltd
Original Assignee
Nevin Electric Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nevin Electric Ltd filed Critical Nevin Electric Ltd
Priority to GB8117990A priority Critical patent/GB2081515B/en
Publication of GB2081515A publication Critical patent/GB2081515A/en
Application granted granted Critical
Publication of GB2081515B publication Critical patent/GB2081515B/en
Expired legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/22—Secondary treatment of printed circuits
    • H05K3/24—Reinforcing the conductive pattern
    • H05K3/243—Reinforcing the conductive pattern characterised by selective plating, e.g. for finish plating of pads
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
    • H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
    • H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
    • H05K3/3457—Solder materials or compositions; Methods of application thereof
    • H05K3/3473—Plating of solder
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K38/00—Medicinal preparations containing peptides
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
    • H05K2203/05—Patterning and lithography; Masks; Details of resist
    • H05K2203/0562—Details of resist
    • H05K2203/0574—Stacked resist layers used for different processes
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/02—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding
    • H05K3/06—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding the conductive material being removed chemically or electrolytically, e.g. by photo-etch process
    • H05K3/061—Etching masks
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
    • H05K3/108—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern by semi-additive methods; masks therefor
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
    • H05K3/18—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using precipitation techniques to apply the conductive material
    • H05K3/181—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using precipitation techniques to apply the conductive material by electroless plating
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
    • H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
    • H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
    • H05K3/3452—Solder masks
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/38—Improvement of the adhesion between the insulating substrate and the metal
    • H05K3/386—Improvement of the adhesion between the insulating substrate and the metal by the use of an organic polymeric bonding layer, e.g. adhesive
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/40—Forming printed elements for providing electric connections to or between printed circuits
    • H05K3/42—Plated through-holes or plated via connections
    • H05K3/425—Plated through-holes or plated via connections characterised by the sequence of steps for plating the through-holes or via connections in relation to the conductive pattern
    • H05K3/426—Plated through-holes or plated via connections characterised by the sequence of steps for plating the through-holes or via connections in relation to the conductive pattern initial plating of through-holes in substrates without metal
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/40—Forming printed elements for providing electric connections to or between printed circuits
    • H05K3/42—Plated through-holes or plated via connections
    • H05K3/425—Plated through-holes or plated via connections characterised by the sequence of steps for plating the through-holes or via connections in relation to the conductive pattern
    • H05K3/427—Plated through-holes or plated via connections characterised by the sequence of steps for plating the through-holes or via connections in relation to the conductive pattern initial plating of through-holes in metal-clad substrates

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Printing Elements For Providing Electric Connections Between Printed Circuits (AREA)
  • Manufacturing Of Printed Wiring (AREA)

Abstract

A circuit board, copper-clad on both sides to 5 to 12 microns thickness, is drilled and the sides of the holes electrolessly plated with copper. The whole board is then electrolytically flash-plated with copper. A negative mask of a desired conductor pattern is printed on both faces and the conductor tracks and sides of the holes are copper plated to a slightly greater thickness than eventually desired. Selected areas of the tracks, including the walls and mouths of the holes are then electrolytically solder plated, using a second mask. Finally both masks are removed and the copper etched to remove the unplated parts of the initial copper layer and leave the desired tracks and holes which are through-plated with solder. As a modification, the circuit board is initially unclad and is subjected to the electroless and flash- plating steps after being drilled and coated with adhesive.

Description

SPECIFICATION Method of making printed circuit boards This invention relates to the production of selectively solder plated printed circuit boards, and particularly to double-sided boards having plated-through holes.
A conventional method will first be described with reference to Fig. 1 of the drawings, in which a number of sequential steps are illustrated.
The conventional method starts as shown at (a) with the use of a double-sided board which is copper clad to a thickness of the order of 35 microns. Holes are drilled through the board (step (b)) at predetermined desired positions, and the sides of the holes are sensitised and electroless copper plated. The whole surface of the plate as well as the sides of the holes are then plated with copper (step (c)) by an electrolytic plating method to the required final thickness.
The next step, step (d), is to print a positive image of the desired conductor pattern onto the two surfaces of the board, using an etch resist. This is usually done with a dry film photographic process in which the holes also are covered, the technique being known as 'tenting'. The board surfaces are then etched, step (e), to leave a copper conductor path with the desired pattern on the board surfaces and extending through the holes. In the following step, step (f), a final solder resist is printed on the board surfaces, leaving only the areas on which solder plating is desired, that is to say around and through the holes.
The board is then immersed in a hot solder bath, step (g), to apply solder to the areas of the board not covered with solder resist, and the board withdrawn and the excess solder blown off. This step is known as solder levelling. This process is known to be hazardous and causes distortion to boards being so produced.
According to the present invention there is provided a method of making a selectively solder plated printed circuit board, comprising providing a circuit board having at least one aperture extending between its opposite faces, plating the walls of the aperture and the faces of the board to form at least an outer portion of a base layer of electrically conducting material, forming first electrically insulating masks on each face of the board to leave regions of each electrically conducting layer exposed to define respective desired conductor track patterns between which the aperture extends, electroplating further electrically conducting material onto the exposed regions and the walls of the aperture, forming second electrically insulating masks to leave exposed for solder plating regions of the track patterns including portions adjacent the mouths of the aperture, electroplating solder onto the exposed regions of the conductor patterns and the walls of the aperture, and removing the base layer of electrically conducting material from the faces of the board to leave the desired conductor track pattern, the first and second masks being removed prior to removal of the base layer.
Preferably, the board provided is clad with electrically conducting material to form an inner portion of the base layer.
A preferred method embodying this invention will now be described with reference to Fig. 2 of the drawings.
Referring to Fig. 2, in step (a) a doublesided copper clad is taken but in this case it is copper clad at a lesser thickness: preferably to less than 15 microns with 5 to 12 microns being more preferred and about 9 microns the most preferable. Holes are drilled through the board (step (b)) at the predetermined desired positions, and the sides of the holes are sensitised and electroless plated with copper.
The surfaces of the board as well as the sides of the holes are next electrolytically flashplated with copper, (step (c)).
In step (d), a negative or reverse mask of a desired conductor pattern is now printed onto both sides of the board using a resist material.
Either dry film or screen printing can be used.
The next step, step (e), is to plate copper onto tracks defined by the mask, to form the desired conductor pattern, and onto the sides of the through holes. Now, in step (f), a plating mask is dry filmed or screen printed onto the top of the reverse mask defining the conductor pattern to leave pad areas exposed around the ends of the through holes. These exposed areas can now be electroplated with lead-tin solder (step (g)) in a solder-plating tank.
Subsequently the mask applied in step (d) and the mask applied in step (f) are simultane ousty removed to reveal the unplated portions of the copper tracks.
Now the board is subjected to a differential etching process. The copper tracks were thickened by plating in step (e), and so the thin copper base foil can be removed while still leaving an adequate thickness for the copper conductors. The resultant board is shown at (h) in Fig. 2. At this point parts of the copper tracks can, if desired, be gold plated, and further holes drilled through the board.
The lead-tin solder on the pads and in the holes is now reflowed and a final solder resist pattern is then printed onto the board. This resist pattern has openings positioned identically to those of the plating mask applied at (f) but, alternatively, the openings may be slightly enlarged. The resulting board is shown at (i) in Fig. 2. The solder plated pads and holes are left exposed for the addition of components and a subsequent wave-soldering operation.
It should be noted that the preferred method of Fig. 2 involves no difficult registra ilion problems of the solder-plating mask with the conductor tracks because in step (g) the conductor tracks are surrounded by the reverse mask applied at step (d) and, therefore, the dimensions and positions of the apertures in the solder-plating mask are not critical because solder is plated only onto the exposed portions of the conductor tracks and not onto the adjacent conductor pattern mask which is of insulating material.
Moreover, with this method, the lead-tin solder does not underlie the final solder resist around the peripheries of the pads and the possibility of damage to the final resist during the wave soldering operation is greatly reduced.
The method of the present invention avoids the solder levelling operation of the conventional method of Fig. 1.
By way of modification, the method may start with an unclad circuit board which is first drilled and then sprayed with adhesive before the sensitising, electroless plating and electrolytic flashplating steps. In this way, a copper layer of about 3 microns thickness is built up.
After heat curing of the adhesive, steps (d) to (i) are performed as describee above. In the differential etching step, a much thinner layer of copper is removed than is the case in the method which starts with a copper-clad board.

Claims (15)

1. A method of marking a selectively solder plated printed circuit board, comprising providing a circuit board having at least one aperture extending between its opposite faces, plating the walls of the aperture and the faces of the board to form at least an outer portion of a base layer of a electrically conducting material, forming first electrically insulating masks on each face of the board to leave regions of each electrically conducting layer exposed to define respective desired conductor track patterns between which the aperture extends, electroplating further electrically conducting material onto the exposed regions and the walls of the aperture, forming second electrically insulating masks to leave exposed for solder plating regions of the track patterns including portions adjacent the mouths of the aperture, electroplating solder onto the exposed regions of the conductor patterns and the walls of the aperture, and removing the base layer of electrically conducting material from the faces of the board to leave the desired conductor track pattern, the first and second masks being removed prior to removal of the base layer.
2. A method according to claim 1,in which the board provided is clad with electrically conducting material to form an inner portion of the base layer.
3. A method according to claim 2, in which the board is clad to a thickness of less than 15 microns.
4. A method according to claim 3, in which the board is clad to a thickness of 5 to 1 2 microns.
5. A method according to claim 4, in which the board is clad to a thickness of about 9 microns.
6. A method according to claim 1, in which the board provided is unclad, the faces of the board being coated with adhesive prior to the first plating step.
7. A method according to any of claims 1 to 6, in which the first plating step includes electroless plating of the walls of the aperture.
8. A method according to claim 7, in which the first plating step includes electrolytic flash plating of the surfaces of the board and the walls of the aperture after the electroless plating operation.
9. A method according to any of claims 1 to 8, in which the electrically conducting material is copper.
10. A method according to any of claims 1 to 9, in which at least one mask is formed by a dry film process.
11. A method according to any of claims 1 to 10, in which at least one mask is formed by a screen printing process.
12. A method according to any of claims 1 to 11, in which the electrically conducting material is removed by etching.
13. A method according to any of claims 1 to 12, including the further step of gold plating portions of the conductor pattern of the board after the electrically conducting material removal step.
14. A method according to any of claims 1 to 13, including the step of applying a solder resist pattern to the final board, the resist pattern and the second mask having apertures of substantially identical position and dimensions.
15. A method of producing a selectively solder plated printed circuit board, the method being substantially as hereinbefore described with reference to Fig. 2 of the drawings or substantially as hereinbefore described with reference to Fig. 2 of the drawings and including the modification hereinbefore described.
1 6. A selectively solder plated printed circuit board produced by a method according to any of claims 1 to 15.
GB8117990A 1980-06-11 1981-06-11 Method of making printed circuit boards Expired GB2081515B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8117990A GB2081515B (en) 1980-06-11 1981-06-11 Method of making printed circuit boards

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8019109 1980-06-11
GB8117990A GB2081515B (en) 1980-06-11 1981-06-11 Method of making printed circuit boards

Publications (2)

Publication Number Publication Date
GB2081515A true GB2081515A (en) 1982-02-17
GB2081515B GB2081515B (en) 1984-10-24

Family

ID=26275811

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8117990A Expired GB2081515B (en) 1980-06-11 1981-06-11 Method of making printed circuit boards

Country Status (1)

Country Link
GB (1) GB2081515B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0517399A1 (en) * 1991-06-05 1992-12-09 Macdermid Incorporated Process for manufacturing printed circuit employing selective provision of solderable coating

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0517399A1 (en) * 1991-06-05 1992-12-09 Macdermid Incorporated Process for manufacturing printed circuit employing selective provision of solderable coating

Also Published As

Publication number Publication date
GB2081515B (en) 1984-10-24

Similar Documents

Publication Publication Date Title
JPH09232741A (en) Printed-wiring board
GB2081515A (en) Method of making printed circuit boards
JPH08107263A (en) Manufacturing method of printed-wiring board
JPS58128791A (en) Method of producing printed circuit board and printed circuit board
JPS6012791A (en) Method of producing printed circuit board
JP3340752B2 (en) Manufacturing method of flexible printed wiring board
JPH0219990B2 (en)
JPH01196196A (en) Formation of soldered layer in printed-circuit board
JPH118465A (en) Manufacture of printed wiring board through additive method
JP2622848B2 (en) Manufacturing method of printed wiring board
JP3130707B2 (en) Printed circuit board and method of manufacturing the same
JPH01295489A (en) Manufacture of printed wiring board and wiring board obtained by this manufacturing method
JPH08186357A (en) Printed wiring board and manufacture thereof
JPS5832798B2 (en) Manufacturing method for printed wiring boards
JP2643125B2 (en) Printing method of printed wiring board
JPH0567871A (en) Printed-wiring board and manufacture thereof
JP2669411B2 (en) Manufacturing method of printed wiring board
JPS613494A (en) Method of producing printed board
JP2000133892A (en) Manufacture of flexible printed wiring board
JPH04152692A (en) Manufacture of printed wiring board
JPH05259624A (en) Printed wiring board and production thereof
JPH0567865A (en) Method of treating surface of printed-wiring board
JPH01217994A (en) Printed wiring board
JPS61181189A (en) Manufacture of printed wiring board
JPH09232729A (en) Printed wiring board manufacturing method and printed wiring board

Legal Events

Date Code Title Description
PCNP Patent ceased through non-payment of renewal fee