US3897323A

US3897323A - Apparatus for selective plating

Info

Publication number: US3897323A
Application number: US495005A
Authority: US
Inventors: Roy Schlotthauer
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 1974-08-05
Filing date: 1974-08-05
Publication date: 1975-07-29
Anticipated expiration: 1992-07-29

Abstract

A method of selective or ''''spot'''' plating, particularly electroplating, of articles including the steps of masking predetermined portions of the article to be plated so that those portions will not be contacted by the plating solution, establishing an electrical connection to conductive portions of the article and then contacting the unmasked portions of the article with plating solution, for sufficient length of time to plate those portions. The apparatus includes means for feeding the article into an apertured conveyor belt which forms the mask between the portions of the article to be plated and those portions which are not to be plated. The masked portion of the article is then contacted by a conductive liquid and the unmasked portion of the article contacted by the plating solution, through means of a reciprocating plating head which travels with the conveyor for a sufficient length of time to affect the plating of the unmasked portions of the article.

Description

United States Patent [191 Schlotthauer [451 July 29, 1975 1 1 APPARATUS FOR SELECTIVE PLATING [75] Inventor: Roy Schlotthauer, Phoenix, Ariz.

[73] Assignee: Motorola, Inc., Chicago, Ill.

[22] Filed: Aug. 5, 1974 [21] Appl. No.: 495,005

Johnson et a1. 204/224 R Primary Examiner'l. M. Tufariello Atmrney. Agenl, 0r Firm-Vincent J. Rauner; Henry T. Olsen [57] ABSTRACT A method of selective or spot plating, particularly electroplating, of articles including the steps of masking predetermined portions of the article to be plated so that those portions will not be contacted by the plating solution, establishing an electrical connection to conductive portions of the article and then contacting the unmasked portions of the article with plating solution, for sufficient length of time to plate those portions. The apparatus includes means for feeding the article into an apertured conveyor belt which forms the mask between the portions of the article to be plated and those portions which are not to be plated. The masked portion of the article is then contacted by a conductive liquid and the unmasked portion of the article contacted by the plating solution, through means of a reciprocating plating head which travels with the conveyor for a sufficient length of time to affect the plating of the unmasked portions of the article.

3 Claims, 5 Drawing Figures SHEET PATENTEI] JUL 2 9 I975 mmdE +oooooooooooooon: D TOOOOOOW APPARATUS FOR SELECTIVE PLATING BACKGROUND OF THE INVENTION This invention is related to a method and apparatus for electroplating articles, and more particularly to a method and apparatus for plating semiconductor package headers.

Previous attempts to selectively plate transistor headers have not been successful, as they have been too cumbersome to be adapted for mass production purposes. By selective plating is meant, as related to transistor headers, the plating of only the base and inner leads of the header and not the outer portion of the base and the outer leads. To accomplish this previously required complicated or manual procedures which were not adaptable to mass production. As a result, most transistor headers have been bulk plated, which is somewhat wasteful of the plating material.

SUMMARY OF THE INVENTION It is therefore an object of the invention to provide a method of selectively plating articles.

A further object of the invention is to selectively plate transistor headers.

A still further object of the invention is to provide a method and apparatus for selectively plating transistor headers which is suitable for mass production.

In accordance with these objects, there is provided a method and apparatus for automatically masking the transistor headers, contacting portions of the transistor header to render those portions to be plated electrically conductive, and then contacting only those portions of the article to be plated with the plating solution.

THE DRAWINGS Further objects and advantages of the invention will be understood from the following complete description and from the drawings wherein:

FIG. 1 is a perspective view somewhat schematically of an assembly line for selectively plating transistor headers in accordance with a preferred embodiment of the invention.

FIGS. 2a and 2b are a top and side view further illustratin g the operation of the apparatus in contacting the transistor headers.

FIG. 3 is a cross-section of a detail illustrating the operation of the apparatus.

FIG. 4 is an exploded view depicting the relationship of the conveyor belt to the electrical contact mechamsm.

COMPLETE DESCRIPTION The method of the present invention will be better understood by reference to the preferred embodiment of the apparatus which, as shown in FIG. 1, includes two parallel conveyor lines 11 and 12. Each conveyor line is fed with articles to be selectively plated from vibratory feeder bowls l3 and 14. The conveyor belts -l1 and 12 then feed the articles to reciprocating plating heads 15 and 16 and then to an unload station whereat the articles can be removed and inspected. All of the foregoing can be mounted on and within a cabinet 17. Since the plating solution may give off undesirable odors and gasses,

hood sections

18 and 19 may be provided over the actual plating area.

After the articles are fed onto the conveyor belt 11 from the feeder, the track of the conveyor slopes downwardly at 30 (FIG. 2) toward the interior of the cabinet support 17 within which a plating solution recovery tank 21 and a pump for circulating the plating solution through the plating heads is located. At the lower part 22 of the conveyor track, the plating head 15 moves down into contact with the articles on the conveyor, then travels with the conveyor while the plating takes place, then moves upwardly and returns to plate the next group of articles, as indicated by the dashed travel line 23. The relationship of the conveyor belt 11 with relation to the plating head and its configuration, is illustrated in detail in FIGS. 3 and 4 wherein it will be noted that the conveyor belt has a plurality of centrally spaced masking apertures 31 centrally located therein and the belt has downwardly curved wings on either side 32. The underside of the conveyor belt is provided with alignment guides 33. The alignment guides 33 cooperate with suitable members of the conveyor pulleys and the contactor tank 34 to maintain the conveyor belt 11 in its proper track. The plating head 15 includes a lower plating chamber 35 defined by downwardly extending

side walls

36, 37 in an upper reservoir chamber 38. Suitable valving means may be provided in the inlet 39 between the reservoir chamber and the plating chamber. Since the plating solution flows continuously from the plating reservoir 38 to the plating chamber 35 during the plating operation, overflow ports 39 provide an outlet for the plating solution, which then drains out over the wings 32 of the conveyor belt 11 for return to the plating tank 21.

Insofar as previously described, the apparatus would be suitable for electroless plating, but is more particularly suitable for electrolytic plating and, therefore, the contactor tank 34 contains a conductive liquid 40, such as mercury, which will establish one electrical connection to the article to be plated. The other electrical connection to the plating solution is provided by a conductive contact 41 lining the inlet port 39. Thus, for example, the contact 41 provides the anode to the plating solution and the conductive liquid 40 provides the cathodic contact, completing the electrolytic plating circurt.

The apparatus is particularly adapted for selectively plating transistor headers. As shown in FIG. 3 the header includes a base 50 and a plurality of leads 57, one of which is electrically connected to the base and the others being insulated therefrom. The level of conductive liquid 40 is such that the leads 57 are in electrical contact therewith.

While the invention has been disclosed by way of certain preferred embodiments, it will be appreciated that suitable modifications may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. Apparatus for selective plating of articles having conductive portions to be plated and conductive portions extending therefrom not to be plated comprising a conveyor belt having apertures; means for feeding the articles into the apertures with the portions not to be plated extending therethrough, thereby masking those portions of the article from contact by the plating solution; means for moving the conveyor belt so that conductive liquid means establish an electrical connection to those portions of the article extending through the belt; and, plating header means for contacting the unmasked portions of the article with plating solution for a sufficient length of time to plate those portions.

4 and through said plating head and whereby said conveyor belt is configured to drain the excess plating solution away from contact with the conductive liquid means.

Claims

1. APPARATUS FOR SELECTIVE PLATING OFARTICLES HAVING CONDUCTIVE PORTIONS TO BE PLATED AND CONDUCTIVE PORTIONS EXTENDING THEREFROM NOT TO BE PLATED COMPRISING A CONVEYOR BELT HAVING APERTURES, MEANS FOR FEEDING THE ARTICLES INTO THE APERTURES WITH THE PORTIONS NOT TO BE PLATED EXTENDING THERETHROUGH, THEREBY MASKING THOSE PORTIONS OF THE ARTICLE FROM CONTACT BY THE PLATING SOLUTION, MEANS FOR MOVING THE CONVEYOR BELT SO THAT CONDUCTIVE LIQUID MEANS ESTABLISH AN ELECTRICAL CONNECTION TO THOSE PORTIONS OF THE ARTCLE EXTENDING THROUGH THE BELT, AND, PLATING HEADER MEANS FOR CONTACTING THE UNMASKED PORTIONS OF THE ARTICLE WITH PLATING SOLUTION FOR A SUFFICIENT LENGT OF TIME TO PLATE THOSE PORTIONS.

2. Apparatus as recited in claim 1 and further including means for reciprocating the plating head means in a rectilinear travel pattern whereby the plating header means travels with the conveyor belt for said time.

3. Apparatus as recited in claim 1 and further including means for effecting the flow of plating solution to and through said plating head and whereby said conveyor belt is configured to drain the excess plating solution away from contact with the conductive liquid means.