CA1137650A - Method for applying adhesive resin on a circuit board - Google Patents
Method for applying adhesive resin on a circuit boardInfo
- Publication number
- CA1137650A CA1137650A CA000350330A CA350330A CA1137650A CA 1137650 A CA1137650 A CA 1137650A CA 000350330 A CA000350330 A CA 000350330A CA 350330 A CA350330 A CA 350330A CA 1137650 A CA1137650 A CA 1137650A
- Authority
- CA
- Canada
- Prior art keywords
- screen
- areas
- blade
- adhesive resin
- resin
- 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.)
- Expired
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
- H05K3/10—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
- H05K3/12—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 thick film techniques, e.g. printing techniques to apply the conductive material or similar techniques for applying conductive paste or ink patterns
- H05K3/1216—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 thick film techniques, e.g. printing techniques to apply the conductive material or similar techniques for applying conductive paste or ink patterns by screen printing or stencil printing
- H05K3/1233—Methods or means for supplying the conductive material and for forcing it through the screen or stencil
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41F—PRINTING MACHINES OR PRESSES
- B41F15/00—Screen printers
- B41F15/14—Details
- B41F15/44—Squeegees or doctors
- B41F15/46—Squeegees or doctors with two or more operative parts
-
- 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
- H05K2203/02—Details related to mechanical or acoustic processing, e.g. drilling, punching, cutting, using ultrasound
- H05K2203/0264—Peeling insulating layer, e.g. foil, or separating mask
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Screen Printers (AREA)
- Electric Connection Of Electric Components To Printed Circuits (AREA)
- Manufacturing Of Printed Wiring (AREA)
- Non-Metallic Protective Coatings For Printed Circuits (AREA)
Abstract
METHOD FOR APPLYING ADHESIVE RESIN
ON A CIRCUIT BOARD
ABSTRACT OF THE DISCLOSURE
A printing screen having a pattern of previous print-ing areas and impervious non-printing areas is angularly dis-placed to an operative position parallel to, but slightly spaced from a substrate on which a resin pattern is to be printed. A resilient blade or squeegee is wiped across the screen in its operative position for both pressing the screen down against the substrate and squeezing semi-liquid resin through the pervious areas into contact with the substrate.
Upon completion of such wiping operation, the resilient blade is lifted from the screen and the screen is maintanied in its operative position parallel to the substrate for a sufficient time to permit the substantially vertical collapse of resin threads bridging the space between the printed pattern and the screen.
-i-
ON A CIRCUIT BOARD
ABSTRACT OF THE DISCLOSURE
A printing screen having a pattern of previous print-ing areas and impervious non-printing areas is angularly dis-placed to an operative position parallel to, but slightly spaced from a substrate on which a resin pattern is to be printed. A resilient blade or squeegee is wiped across the screen in its operative position for both pressing the screen down against the substrate and squeezing semi-liquid resin through the pervious areas into contact with the substrate.
Upon completion of such wiping operation, the resilient blade is lifted from the screen and the screen is maintanied in its operative position parallel to the substrate for a sufficient time to permit the substantially vertical collapse of resin threads bridging the space between the printed pattern and the screen.
-i-
Description
~a~L3~6~
B~CE~GROUND OF TIIE INVENTION
Field of the Invention . .
This invention relates generally to an apparatus for applying adhesive resin on a surface, and, more particularly, is directed to an apparatus for applying adhesive resin in a pattern on a circuit board, for example, for use in temporarîly holding chip-type circuit ele~ents or parts on the circuit board.
.
~escription of the Prior Art Printed circuit boards are used for mounting parts to be included in a desired circuit. Such parts are normally temporarily affixed to holes or ?ins in the circuit board by their wire leadsJ and a subsequent soldering operation per-manently af~ixes the parts to the circuit board.
`~Chip-type circuit parts are used to increase the density of the circuit parts and to permit reduction of the size of the printed circuit board. Chip-ty e circuit parts are generally cylindrical objects having cap-like contact pads on their ends rather than wire leads. Accordingly, chip-type circuit parts cannot be temporarily attached to the prin-ted circuit board by wire leads in the normal manner prior to soldering.
Adhesive resin may be used for temporarily attaching chip-type parts to a printed circuit board. The adhesive resin is applied to the printed circuit board in a predetermined pat-tern corresponding to the positions where chip-~ype parts are to be mounted. The chip-type parts are then temporarily attached by the adhesive resin to be printed circuit board with ~;
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their contact pads aligned with metallic conductors previously printed on the substrate. The printed circuit board with the attached chip-~ype and other parts is soldered in a conventional soldering operation. In this way, the contact pads of the chip-type parts are soldered to the printed circuit board for permanent mechanical and electrical attachment thereto.
A preferred method of producing the predetennined pattern of adhesive resin includes a silk screening operation in which a fabric screen formed of silk, organdy but preferably of polyester, and having a pattern~of pervious printing areas and impervious non-printing areas formed thereon, is stretched across a supporting frame and is disposed in confronting or face to face relation to the printed circuit board. The adhe-sive resin is squeezed through the pervious printing areas onto the surface of the printed circuit board to duplica~e the pattern thereon. The supporting frame is then an~ularly displaced ~way From the printed circuit board. When the sup-porting frame is thus displaced, resin threads bridging the space between the screen and the printed circuit board are ~
stretched and laterally inclined until they break and fall on the printed circuit board adjacent the desired resin-receiving areas. Portions of the printed circuit board which are not intended to receive resin, such as the conductive patterns, may be covered by the collapsed resin threads. When portions of the conductive patterns which are provided for solder attach-ment of the contact pads of the chip-type parts become covered with the resin threads, a good solder joint cannot be made.
The thicker the layer of adhesive resin deposited on the cir-cuit board, the more difficulty is encountered by covera~e with resin threads outside the desired resin-receiving areas~
~376~
OBJECTS AND SUM?~ARY OF THE INVEl`ITIOM
_ An object of this invention is to provide an appara-tus for applying adhesive resin in a predetermined pattern to a circuit board in which the adhesive resin is limited to the ?redetermined pattern.
Another object of this invention is to provide an apparatus for applying a predetermined pattern of adhesive resin to a circuit board, and which avoids the formation of resin threads between the circuit board and the screen which fall to the circuit board outside the predetermined pattern.
A further object of this invention is to provide a method for applying a predetermined pattern of adhesive resin to a circuit board and which avoids the deposit of resin on portions of the circuit board not :included within the predeter-mined pattern.
`According to an aspect o~ the invention, an apparatus for ap~lying a pattern of adhesive resin on a surface fixed in a predetermined position comprises a screen having pervious printing areas in the pattern, means for positioning the screen parallel to the surface, means for squeezing the adhesive resin through the printing areas onto the surface, and means for hold-ing the screen parallel to and spaced a predetermined distance from the surface for a predetermined time after actuation of the means for squeezing.
According to a feature of the invention, a method of applying a pattern of adhesive resin on a substantially planar surface by means of a screen stretched across a frame and having pervious printing areas in the pattern comprises scraping the adhesive resin over the screen to scrape the adhe-~ 3 7~ ~ ~
sive resin into the pervious printing areas, holding the screen parallel to and spaced a predetermined distance from the sur-~: face, contacting the screen with a squeegee with sufficientforce to deflect the screen into contact with the surfac~, translating the squeegee across the screen whereby the adhe-sivP resip in the pervious printing areas is adhered ~o the surface, moving the squeegee away from the screen to permit the screen to resume its undeflected condition parallel to and spaced the predetermined distance from the surface, and continui~ng to hold the screen parallel to and spaced the predetermined distance from the surface until resin threads bridging the space between the surface and the screen brea~
and fall~back into respective printed areas on the surface.
More particularly, there ~s p:rovided:
A method of applying a desired pattern of an ad-hesive resin on a substantially horizolltal planar surface using a tensioned screen having p~svi~us printing areas arranged in : said pattern compris~ng;
scraping said adhesive resin over said screen to scrape amounts o~ said adhesi~e xesin into said pervious printing areas;
holding said screen in an operative position parallel to and spaced a predetermined distance above said substantially horizontal surface;
pressing a squeezing blade downwardly against the operatively positioned screen with ~u~ficient force to deflect a portion of said ten~ioned screen engaged by said blade down-wardly into contact with said surface;
translating the down~ardly;pressed squeezing blade 30 acrosS said screen whereby said amounts of adhesive resin in said perviou~ printin~ areas are squeezed therefrom and adherPd ~ . . .
~L~376~C~
to underlying respective areas of ~aid surface;
moving ~aid blade away from the operatively positioned screen to permi~ the tension of the latter to cause said screen to resume its undeflected condition parallel to and spaced up-wardly said predetermined distance from said eurface with threads of said adhesive resin initially bridging said distance between said printing areas of the screen and said underlying areas of the surface;
continuin~ to hold said screen in said operative po sition parallel to and spaced said predetermined distance from aid surface as said resin threads break and fall back substan~
tially vertically into the respecti~e ones of said underlying areas; and removing said screen from said operative position only after all of said resin threads have broken and fallen back into said respective underlying areas for ensuring that the margins of the latter are sharply defined.
There is also provided.
~ Apparatus for applying a desirea pattern of adhesive :~: 20 resin to a substantially horizontal plane surface comprising:
a screen having pervious printing areas in said pat- :
tern;
: a frame across which said screen is stretched;
means for pivoting said frame between first and second positions;
said first position being effective to normally dis pose said screen parallel to, and spaced from, said surface;
said second position being effective to dispose said screen a substantial distance away from said surface;
a scraping blade;
means for contacting said scraping blade with said screen across a first dimension of the latter;
-4a-~ .. .. . .. .. . . .. . .
~37~54~
means for translating said scxaping blade in contact with said screen acro-~s a second dimensi~n of said screen where-by an amount of said adhesive resin is scraped into said per-vious printing areas;
a squeezing blade;
means, effective when said frame is in said first ~` position~ for pressing said squeezing blade against said screenacross a first dimension of said screen with sufficient force to deflect a portion o said screen contacted by said squeezing blade in~o contact with said surface;
means for translating said squeezing bla~e in contact with said screen across a second dimension of said screen whereby said adhesive resin in said pervious printing areas i.s squeezed from the latter and deposited in respective areas on said surface; :~
means or moving said squeezing blade out of contact with said screen while said frame remains in said first position;
and ~:
mean~ for holding said frame in said first position for a sufficient time after actuation of said means for moving the squeezing blade to permit resin threads bridging between said screen and the deposited areas on said surface to bxeak and ~-fall back into the respective deposited areas. ::
There Is also provided:
A method of applyi~g a desired pattern of adhesive re~in on a su~stantiall~ horizontal planar surface using a screen having perYious printing areas arranged in said pattern compris-i~g:
scraping said adhesive resin over said screen to scrape said adhesive resin înto said pervious printing areas;
holding said screen parallel to and spaced a predeter-mined distance from said surface;
pre~sin~ a squeezin~ blade again t said screen with sufficient force to deflect a portion of said screen engaged -4b-` ~13~5~
by said blade into contact with said sur~ace;
translating said blade across said scxeen whereby said adhesiv~ resin in said pervious printin~ areas is squeezed therefrom and adhered to underlying respective areas o said surface;
moving said blade away from said screen to permit said ~ screen to resume its undeflected condition parallel to and : spaced said predetermined distance from said surface; and continuing to hold said screen parallel to and spaced :
said predetermlned distance from said surface until resin threads bridging between said printin~ areas of said screen and said underlying areas of the surface break and fall back into said underlying areas.
The above, and other obj ects, features and advan- .
tages of the present invention, will become apparent fro~ the .. ~. .. .
following~description read in con~unction with the acco~any-ing drawings in which li~e reference nunerals designate the same elements.
.' .. . .
BRIEF DESCRIPTIO~I OF THE DR~JIN~S
Fig. 1 iS an overall schematic side elevational view of an ap~aratus for applying adhesive resin to a ~rinted cir-cuit board according to one embodiment of the invention; : -~
Fig. 2 is an enlarged cross-sectional view taken .` .
along the line II-II of Fig. l;
Fig. 3 is an enlarged cross-sectional view taken along the line III-III of Fig. l;
Fig. 4 is a cross-sectional view taken along the line IY-IV of Fig. 3; ' Figs. 5-8 and 10-12 are diagram~atic side views of --~c--` :~13765t~
the apparatus of Fig. 1 to which reference will be made in describing the operation thereof in accordance with the pre-sent invention; and Fig. 9 is a diagrammatic side view similar to that of Fig. 12, but to which reference will be made in describing the problem encountered with the prior art.
..
D~TAI~ED DESCRIPTIOr~ OF THE PREF~RR~D EMBODI~NT
Referring to Fig. 1, it will be seen that an apparatus for applying adhesive resin on a printed circuit board in accor-dance with one embodiment of this invention includes a base 1 on a supporting pla~e 11 for carry:ing a mounting plate 2 on which a printed circuit board 3 may be mounted. ~ bracket 4 is fixed at each side of base 1 and supports a respective pivot pin 5. A rectangular frame 6 is p:ivotally supported, at one end, on pins 5. A crank arm 7 is fixedly attached to frame 6, and the lower or free end of crank arm 7 is connected through a pin 10 to a piston rod 9 of a hydraulic or oil pressure cylin-der ~ and to a link 12. Link 12 and oil pressure cylinder 8 are hinged at their lwoer ends to supporting plate 11. ~Frame ~. may thus be angularly displaced about pins 5 by extension and retraction of pi.ston rod 9 of oil pressure cylinder 8.
Crank arm 7, oil pressure cylinder 8, piston rod 9, link 12 and pin 10 mlay optionally be duplicated at the opposite side of frame 6 for balanced actuation thereof.
Referring now also to Figs. 2 and 3, frame 6 is shown to have a screen 13 stretched across it at a predetermined tension. Screen 13 is a fabric mesh of any suitable material, but is preferably a polyester synthetic fiber, such as the rnaterial sold under the -trademark Tetoron. Both surfaces of ~1 3 7~ ~
screen 13 are coated with an impervious resin except for per-vious printing areas 14 which permit the passage of liquid or semi-liquid adhesive through the uncoated meshes thereof. The thickness of the impervious non-printing areas of screen 13 is approximately equal to the thickness of adhesive resin which it is desired to apply to selected areas of printed ~cir-cuit board 3. In the preferred embodiment, the thickness of the impervlous areas is about 400~ to about 500~. Adhesiv~e resin is squeezed through the meshes of printing areas 14 of screen 13 onto printed circuit board 3 by a squeeze member or squeegee to be described hereinafter.
Supportlng members 15 (Fig. 1), at each side of the front and rear of frame 6, support a pair of rods 16 substan-tially parallel to the sides of frame 6. Slide blocks 17 on slide bearings 18 (Fig. 3) are slideable along rods 16 either manually Qr by conventional drive ~eans (not shown).
A pair of air cylinders l9 and 20 are provided for each slide block 17 and have their piston rods attached to : : .
stepped portions 17a of the respective slide blocks 17. A ~ -bar 21 is connected between air cylinders 1~ (Fig. 3). A
squeegee consisting of a U-shaped support bar 23 holding a resiliently flexible wiping blade 24, is connected to bar 21 by adjustable screws 22. Blade 24 extends over substantially the entire width of screen 13 and is preerably of rubber-like material, such as, urethane rubber.
A second bar 21' is connected between air cylinders 20. A scraper consisting of a U-shaped support bar 25 holding a scraping blade 26 is attached through adjustable screws 22' to bar 21'. Scraping blade also extends over substantially the entire width of screen 13 and is also preferably of a 76~r~
resilient Material, such as, urethane rubber.
As will be eviden~ to one skilled in the art, actua-tion of air cylinders 19 is effective to move wiping blade 2 toward and away from screen 13. Similarly, actuation of air cylinders 20 is effective to move scraping blade 26 toward and away from screen 13.
Although air cylinders 19 and 20 are shown with their piston rods attached to slide blocks 17 and their cyjlin-ders attached to bars 21 and 21', respectively, it is apparent that the cylinders of air cylinders 19 and 20 may alternative-ly be attached to slide blocks 17 while their piston rods are there connected to bars 21 and 21', respectively.
iping or squeegee blade 24 and scraping blade 26 are inclined relative to the normal or undeflected plane of screen 13 (Fi~. 4) in opposite directions at angles of from 45 to 60. Such inclination of blades 2~ and 26 and the use of resilient urethane rubber for these parts reduces the inci-:
dence of damage to, and increases the life of screen 13.
P~eferrinw now to Fi~. 5, it will be seen that frame 6 is initially angularly displaced by cylinder 8 in the clock-wise direction about pins 5 into the illustrated inclined . .
elevated posi~ion. An amount of adhesive resin 27 is applied across screen 13 by any conventional means (not sho~m) and air cylinders 20 are actuated to lower scraping blade 26 toward, or into contact with, the upper surface or screen 13, as indi-cated by the arrow.
As shown on Fig. 6, support bar 25 and scraping blade 26 are moved leftward with slide blocks 17 by a conven-tional drive apparatus (not sho~m) or manually during which the semi-fluid adhesive resin 27 is scraped across screen 13 ~l3~6S0 by scraping blade 26. Printirlg areas 14 are thus filled with adhesive resin, and then air cylinders 20 are actuated to raise scraping blade 26 from screen 13.
Frame 6 is angularly displaced in the counter-clock-wise direction about pins 5 into the ~osition shown in Fig. 7, and in which frame 6 is parallel to but spaced a predetermined distance from the horizontal surface of printed circuit board 3.
Air cylinders 19 are actuated to force squeegee or wiping blade 24 downward against screen 13, as shown by the arrow, with sufficient force to deflect screen 13 from its normal plane shown in dot-dash lines on Fig. 7 into contact with the surface of printed circuit board 3 as shown by the solid line.
Slide blocks 17 are now moved rightward (in Figs.
7 and 8) drawing squeegee or wiping blade 24 with them. The adhesive resin previously scraped into printing areas 14 by scraying blade 26 is now pressed therethrough and adhered to the surface of printed circuit board 3 as blade 24 presses screen 13 into contact therewith, thus leaving a thickness of adhesive resin 27 on printed circuit board 3 in a pattern corresponding to pervious printing areas 14 of screen 13.
Any excess adhesive resin is moved alon~ ahead of blade 24.
Squee~ee blade 24 is moved fully to the right, as shown in Fig. 10, and air cylinders 19 are actuated to raise blade 24 from screen 13. This permits screen 13 to resume its undepressed shape in which it is parallel to, but spaced from printed circuit board 3.
. , Immediately after forming the desired areas of adhe-sive resin 27 on printed circuit board 3 and the return of screen 13 to its undepressed shape, resin threads 28 (Fig. 10) : -8~
~3765~
brldge the space between the individual pattern areas of adhe-sive resin 27 deposited on printed circuit board 3 and the respective printin~ areas 14 i~mediately thereabove.
In the prior art, frame 6 and screen 13 are angularly displaced to their initial inoperative positions shown in Fig. 9 immediately following the return of blade 24 to the position shown on Fig. 10. Such angular displacement of frame 6 and screen 13 stretches resin threads 28 until the latter break. Due to the elongation and breaking of resin threads 28, the material thus pulled from adhesive resin 27 may fall upon unintended areas of printed circuit board 3 and make satis-factory solder connections thereto impossible. This problem is especially severe at the printing areas 14 nearer to pivot pins 5 due to the fact that these areas are relatively closer to the center of rotation and the elon~ated resin threads 2~
extending therefrom are thus more inclined to the surface of printed circuit board 3.
In ordPr to solve the above proble~, in accordance with this invention, frame 6 and screen 13 are maintained in the position of Fig. 10 for a long enough period, suitably two to six seconds after the return of blade 24 to the position shown on Fig. 10, until the fluidity of the resin and its sur-face tension cause resin threads 28 to break, as is shown on Fig. 11. Since resin threads 28 extend straight upward or ver~
tically from coated areas of circuit board 3 until they are broken as described above, there is no tendency for these threads to fall over onto unintended areas of printed circuit board,3. After resin threads 28 break and fall to the surface of their respective pattern areas, surface tension smooths the tops of the pattern areas.
B~CE~GROUND OF TIIE INVENTION
Field of the Invention . .
This invention relates generally to an apparatus for applying adhesive resin on a surface, and, more particularly, is directed to an apparatus for applying adhesive resin in a pattern on a circuit board, for example, for use in temporarîly holding chip-type circuit ele~ents or parts on the circuit board.
.
~escription of the Prior Art Printed circuit boards are used for mounting parts to be included in a desired circuit. Such parts are normally temporarily affixed to holes or ?ins in the circuit board by their wire leadsJ and a subsequent soldering operation per-manently af~ixes the parts to the circuit board.
`~Chip-type circuit parts are used to increase the density of the circuit parts and to permit reduction of the size of the printed circuit board. Chip-ty e circuit parts are generally cylindrical objects having cap-like contact pads on their ends rather than wire leads. Accordingly, chip-type circuit parts cannot be temporarily attached to the prin-ted circuit board by wire leads in the normal manner prior to soldering.
Adhesive resin may be used for temporarily attaching chip-type parts to a printed circuit board. The adhesive resin is applied to the printed circuit board in a predetermined pat-tern corresponding to the positions where chip-~ype parts are to be mounted. The chip-type parts are then temporarily attached by the adhesive resin to be printed circuit board with ~;
~L3~765~
their contact pads aligned with metallic conductors previously printed on the substrate. The printed circuit board with the attached chip-~ype and other parts is soldered in a conventional soldering operation. In this way, the contact pads of the chip-type parts are soldered to the printed circuit board for permanent mechanical and electrical attachment thereto.
A preferred method of producing the predetennined pattern of adhesive resin includes a silk screening operation in which a fabric screen formed of silk, organdy but preferably of polyester, and having a pattern~of pervious printing areas and impervious non-printing areas formed thereon, is stretched across a supporting frame and is disposed in confronting or face to face relation to the printed circuit board. The adhe-sive resin is squeezed through the pervious printing areas onto the surface of the printed circuit board to duplica~e the pattern thereon. The supporting frame is then an~ularly displaced ~way From the printed circuit board. When the sup-porting frame is thus displaced, resin threads bridging the space between the screen and the printed circuit board are ~
stretched and laterally inclined until they break and fall on the printed circuit board adjacent the desired resin-receiving areas. Portions of the printed circuit board which are not intended to receive resin, such as the conductive patterns, may be covered by the collapsed resin threads. When portions of the conductive patterns which are provided for solder attach-ment of the contact pads of the chip-type parts become covered with the resin threads, a good solder joint cannot be made.
The thicker the layer of adhesive resin deposited on the cir-cuit board, the more difficulty is encountered by covera~e with resin threads outside the desired resin-receiving areas~
~376~
OBJECTS AND SUM?~ARY OF THE INVEl`ITIOM
_ An object of this invention is to provide an appara-tus for applying adhesive resin in a predetermined pattern to a circuit board in which the adhesive resin is limited to the ?redetermined pattern.
Another object of this invention is to provide an apparatus for applying a predetermined pattern of adhesive resin to a circuit board, and which avoids the formation of resin threads between the circuit board and the screen which fall to the circuit board outside the predetermined pattern.
A further object of this invention is to provide a method for applying a predetermined pattern of adhesive resin to a circuit board and which avoids the deposit of resin on portions of the circuit board not :included within the predeter-mined pattern.
`According to an aspect o~ the invention, an apparatus for ap~lying a pattern of adhesive resin on a surface fixed in a predetermined position comprises a screen having pervious printing areas in the pattern, means for positioning the screen parallel to the surface, means for squeezing the adhesive resin through the printing areas onto the surface, and means for hold-ing the screen parallel to and spaced a predetermined distance from the surface for a predetermined time after actuation of the means for squeezing.
According to a feature of the invention, a method of applying a pattern of adhesive resin on a substantially planar surface by means of a screen stretched across a frame and having pervious printing areas in the pattern comprises scraping the adhesive resin over the screen to scrape the adhe-~ 3 7~ ~ ~
sive resin into the pervious printing areas, holding the screen parallel to and spaced a predetermined distance from the sur-~: face, contacting the screen with a squeegee with sufficientforce to deflect the screen into contact with the surfac~, translating the squeegee across the screen whereby the adhe-sivP resip in the pervious printing areas is adhered ~o the surface, moving the squeegee away from the screen to permit the screen to resume its undeflected condition parallel to and spaced the predetermined distance from the surface, and continui~ng to hold the screen parallel to and spaced the predetermined distance from the surface until resin threads bridging the space between the surface and the screen brea~
and fall~back into respective printed areas on the surface.
More particularly, there ~s p:rovided:
A method of applying a desired pattern of an ad-hesive resin on a substantially horizolltal planar surface using a tensioned screen having p~svi~us printing areas arranged in : said pattern compris~ng;
scraping said adhesive resin over said screen to scrape amounts o~ said adhesi~e xesin into said pervious printing areas;
holding said screen in an operative position parallel to and spaced a predetermined distance above said substantially horizontal surface;
pressing a squeezing blade downwardly against the operatively positioned screen with ~u~ficient force to deflect a portion of said ten~ioned screen engaged by said blade down-wardly into contact with said surface;
translating the down~ardly;pressed squeezing blade 30 acrosS said screen whereby said amounts of adhesive resin in said perviou~ printin~ areas are squeezed therefrom and adherPd ~ . . .
~L~376~C~
to underlying respective areas of ~aid surface;
moving ~aid blade away from the operatively positioned screen to permi~ the tension of the latter to cause said screen to resume its undeflected condition parallel to and spaced up-wardly said predetermined distance from said eurface with threads of said adhesive resin initially bridging said distance between said printing areas of the screen and said underlying areas of the surface;
continuin~ to hold said screen in said operative po sition parallel to and spaced said predetermined distance from aid surface as said resin threads break and fall back substan~
tially vertically into the respecti~e ones of said underlying areas; and removing said screen from said operative position only after all of said resin threads have broken and fallen back into said respective underlying areas for ensuring that the margins of the latter are sharply defined.
There is also provided.
~ Apparatus for applying a desirea pattern of adhesive :~: 20 resin to a substantially horizontal plane surface comprising:
a screen having pervious printing areas in said pat- :
tern;
: a frame across which said screen is stretched;
means for pivoting said frame between first and second positions;
said first position being effective to normally dis pose said screen parallel to, and spaced from, said surface;
said second position being effective to dispose said screen a substantial distance away from said surface;
a scraping blade;
means for contacting said scraping blade with said screen across a first dimension of the latter;
-4a-~ .. .. . .. .. . . .. . .
~37~54~
means for translating said scxaping blade in contact with said screen acro-~s a second dimensi~n of said screen where-by an amount of said adhesive resin is scraped into said per-vious printing areas;
a squeezing blade;
means, effective when said frame is in said first ~` position~ for pressing said squeezing blade against said screenacross a first dimension of said screen with sufficient force to deflect a portion o said screen contacted by said squeezing blade in~o contact with said surface;
means for translating said squeezing bla~e in contact with said screen across a second dimension of said screen whereby said adhesive resin in said pervious printing areas i.s squeezed from the latter and deposited in respective areas on said surface; :~
means or moving said squeezing blade out of contact with said screen while said frame remains in said first position;
and ~:
mean~ for holding said frame in said first position for a sufficient time after actuation of said means for moving the squeezing blade to permit resin threads bridging between said screen and the deposited areas on said surface to bxeak and ~-fall back into the respective deposited areas. ::
There Is also provided:
A method of applyi~g a desired pattern of adhesive re~in on a su~stantiall~ horizontal planar surface using a screen having perYious printing areas arranged in said pattern compris-i~g:
scraping said adhesive resin over said screen to scrape said adhesive resin înto said pervious printing areas;
holding said screen parallel to and spaced a predeter-mined distance from said surface;
pre~sin~ a squeezin~ blade again t said screen with sufficient force to deflect a portion of said screen engaged -4b-` ~13~5~
by said blade into contact with said sur~ace;
translating said blade across said scxeen whereby said adhesiv~ resin in said pervious printin~ areas is squeezed therefrom and adhered to underlying respective areas o said surface;
moving said blade away from said screen to permit said ~ screen to resume its undeflected condition parallel to and : spaced said predetermined distance from said surface; and continuing to hold said screen parallel to and spaced :
said predetermlned distance from said surface until resin threads bridging between said printin~ areas of said screen and said underlying areas of the surface break and fall back into said underlying areas.
The above, and other obj ects, features and advan- .
tages of the present invention, will become apparent fro~ the .. ~. .. .
following~description read in con~unction with the acco~any-ing drawings in which li~e reference nunerals designate the same elements.
.' .. . .
BRIEF DESCRIPTIO~I OF THE DR~JIN~S
Fig. 1 iS an overall schematic side elevational view of an ap~aratus for applying adhesive resin to a ~rinted cir-cuit board according to one embodiment of the invention; : -~
Fig. 2 is an enlarged cross-sectional view taken .` .
along the line II-II of Fig. l;
Fig. 3 is an enlarged cross-sectional view taken along the line III-III of Fig. l;
Fig. 4 is a cross-sectional view taken along the line IY-IV of Fig. 3; ' Figs. 5-8 and 10-12 are diagram~atic side views of --~c--` :~13765t~
the apparatus of Fig. 1 to which reference will be made in describing the operation thereof in accordance with the pre-sent invention; and Fig. 9 is a diagrammatic side view similar to that of Fig. 12, but to which reference will be made in describing the problem encountered with the prior art.
..
D~TAI~ED DESCRIPTIOr~ OF THE PREF~RR~D EMBODI~NT
Referring to Fig. 1, it will be seen that an apparatus for applying adhesive resin on a printed circuit board in accor-dance with one embodiment of this invention includes a base 1 on a supporting pla~e 11 for carry:ing a mounting plate 2 on which a printed circuit board 3 may be mounted. ~ bracket 4 is fixed at each side of base 1 and supports a respective pivot pin 5. A rectangular frame 6 is p:ivotally supported, at one end, on pins 5. A crank arm 7 is fixedly attached to frame 6, and the lower or free end of crank arm 7 is connected through a pin 10 to a piston rod 9 of a hydraulic or oil pressure cylin-der ~ and to a link 12. Link 12 and oil pressure cylinder 8 are hinged at their lwoer ends to supporting plate 11. ~Frame ~. may thus be angularly displaced about pins 5 by extension and retraction of pi.ston rod 9 of oil pressure cylinder 8.
Crank arm 7, oil pressure cylinder 8, piston rod 9, link 12 and pin 10 mlay optionally be duplicated at the opposite side of frame 6 for balanced actuation thereof.
Referring now also to Figs. 2 and 3, frame 6 is shown to have a screen 13 stretched across it at a predetermined tension. Screen 13 is a fabric mesh of any suitable material, but is preferably a polyester synthetic fiber, such as the rnaterial sold under the -trademark Tetoron. Both surfaces of ~1 3 7~ ~
screen 13 are coated with an impervious resin except for per-vious printing areas 14 which permit the passage of liquid or semi-liquid adhesive through the uncoated meshes thereof. The thickness of the impervious non-printing areas of screen 13 is approximately equal to the thickness of adhesive resin which it is desired to apply to selected areas of printed ~cir-cuit board 3. In the preferred embodiment, the thickness of the impervlous areas is about 400~ to about 500~. Adhesiv~e resin is squeezed through the meshes of printing areas 14 of screen 13 onto printed circuit board 3 by a squeeze member or squeegee to be described hereinafter.
Supportlng members 15 (Fig. 1), at each side of the front and rear of frame 6, support a pair of rods 16 substan-tially parallel to the sides of frame 6. Slide blocks 17 on slide bearings 18 (Fig. 3) are slideable along rods 16 either manually Qr by conventional drive ~eans (not shown).
A pair of air cylinders l9 and 20 are provided for each slide block 17 and have their piston rods attached to : : .
stepped portions 17a of the respective slide blocks 17. A ~ -bar 21 is connected between air cylinders 1~ (Fig. 3). A
squeegee consisting of a U-shaped support bar 23 holding a resiliently flexible wiping blade 24, is connected to bar 21 by adjustable screws 22. Blade 24 extends over substantially the entire width of screen 13 and is preerably of rubber-like material, such as, urethane rubber.
A second bar 21' is connected between air cylinders 20. A scraper consisting of a U-shaped support bar 25 holding a scraping blade 26 is attached through adjustable screws 22' to bar 21'. Scraping blade also extends over substantially the entire width of screen 13 and is also preferably of a 76~r~
resilient Material, such as, urethane rubber.
As will be eviden~ to one skilled in the art, actua-tion of air cylinders 19 is effective to move wiping blade 2 toward and away from screen 13. Similarly, actuation of air cylinders 20 is effective to move scraping blade 26 toward and away from screen 13.
Although air cylinders 19 and 20 are shown with their piston rods attached to slide blocks 17 and their cyjlin-ders attached to bars 21 and 21', respectively, it is apparent that the cylinders of air cylinders 19 and 20 may alternative-ly be attached to slide blocks 17 while their piston rods are there connected to bars 21 and 21', respectively.
iping or squeegee blade 24 and scraping blade 26 are inclined relative to the normal or undeflected plane of screen 13 (Fi~. 4) in opposite directions at angles of from 45 to 60. Such inclination of blades 2~ and 26 and the use of resilient urethane rubber for these parts reduces the inci-:
dence of damage to, and increases the life of screen 13.
P~eferrinw now to Fi~. 5, it will be seen that frame 6 is initially angularly displaced by cylinder 8 in the clock-wise direction about pins 5 into the illustrated inclined . .
elevated posi~ion. An amount of adhesive resin 27 is applied across screen 13 by any conventional means (not sho~m) and air cylinders 20 are actuated to lower scraping blade 26 toward, or into contact with, the upper surface or screen 13, as indi-cated by the arrow.
As shown on Fig. 6, support bar 25 and scraping blade 26 are moved leftward with slide blocks 17 by a conven-tional drive apparatus (not sho~m) or manually during which the semi-fluid adhesive resin 27 is scraped across screen 13 ~l3~6S0 by scraping blade 26. Printirlg areas 14 are thus filled with adhesive resin, and then air cylinders 20 are actuated to raise scraping blade 26 from screen 13.
Frame 6 is angularly displaced in the counter-clock-wise direction about pins 5 into the ~osition shown in Fig. 7, and in which frame 6 is parallel to but spaced a predetermined distance from the horizontal surface of printed circuit board 3.
Air cylinders 19 are actuated to force squeegee or wiping blade 24 downward against screen 13, as shown by the arrow, with sufficient force to deflect screen 13 from its normal plane shown in dot-dash lines on Fig. 7 into contact with the surface of printed circuit board 3 as shown by the solid line.
Slide blocks 17 are now moved rightward (in Figs.
7 and 8) drawing squeegee or wiping blade 24 with them. The adhesive resin previously scraped into printing areas 14 by scraying blade 26 is now pressed therethrough and adhered to the surface of printed circuit board 3 as blade 24 presses screen 13 into contact therewith, thus leaving a thickness of adhesive resin 27 on printed circuit board 3 in a pattern corresponding to pervious printing areas 14 of screen 13.
Any excess adhesive resin is moved alon~ ahead of blade 24.
Squee~ee blade 24 is moved fully to the right, as shown in Fig. 10, and air cylinders 19 are actuated to raise blade 24 from screen 13. This permits screen 13 to resume its undepressed shape in which it is parallel to, but spaced from printed circuit board 3.
. , Immediately after forming the desired areas of adhe-sive resin 27 on printed circuit board 3 and the return of screen 13 to its undepressed shape, resin threads 28 (Fig. 10) : -8~
~3765~
brldge the space between the individual pattern areas of adhe-sive resin 27 deposited on printed circuit board 3 and the respective printin~ areas 14 i~mediately thereabove.
In the prior art, frame 6 and screen 13 are angularly displaced to their initial inoperative positions shown in Fig. 9 immediately following the return of blade 24 to the position shown on Fig. 10. Such angular displacement of frame 6 and screen 13 stretches resin threads 28 until the latter break. Due to the elongation and breaking of resin threads 28, the material thus pulled from adhesive resin 27 may fall upon unintended areas of printed circuit board 3 and make satis-factory solder connections thereto impossible. This problem is especially severe at the printing areas 14 nearer to pivot pins 5 due to the fact that these areas are relatively closer to the center of rotation and the elon~ated resin threads 2~
extending therefrom are thus more inclined to the surface of printed circuit board 3.
In ordPr to solve the above proble~, in accordance with this invention, frame 6 and screen 13 are maintained in the position of Fig. 10 for a long enough period, suitably two to six seconds after the return of blade 24 to the position shown on Fig. 10, until the fluidity of the resin and its sur-face tension cause resin threads 28 to break, as is shown on Fig. 11. Since resin threads 28 extend straight upward or ver~
tically from coated areas of circuit board 3 until they are broken as described above, there is no tendency for these threads to fall over onto unintended areas of printed circuit board,3. After resin threads 28 break and fall to the surface of their respective pattern areas, surface tension smooths the tops of the pattern areas.
Claims (3)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of applying a desired pattern of an ad-hesive resin on a substantially horizontal planar surface using a tensioned screen having pervious printing areas arranged in said pattern comprising;
scraping said adhesive resin over said screen to scrape amounts of said adhesive resin into said pervious printing areas;
holding said screen in an operative position parallel to and spaced a predetermined distance above said substantially horizontal surface;
pressing a squeezing blade downwardly against the operatively positioned screen with sufficient force to deflect a portion of said tensioned screen engaged by said blade down-wardly into contact with said surface;
translating the downwardly pressed squeezing blade across said screen whereby said amounts of adhesive resin in said pervious printing areas are squeezed therefrom and adhered to underlying respective areas of said surface;
moving said blade away from the operatively positioned screen to permit the tension of the latter to cause said screen to resume its undeflected condition parallel to and spaced up-wardly said predetermined distance from said surface with threads of said adhesive resin initially bridging said distance between said printing areas of the screen and said underlying areas of the surface;
continuing to hold said screen in said operative po-sition parallel to and spaced said predetermined distance from said surface as said resin threads break and fall back substan-tially vertically into the respective ones of said underlying areas; and removing said screen from said operative position only after all of said resin threads have broken and fallen back into said respective underlying areas for ensuring that the margins of the latter are sharply defined.
scraping said adhesive resin over said screen to scrape amounts of said adhesive resin into said pervious printing areas;
holding said screen in an operative position parallel to and spaced a predetermined distance above said substantially horizontal surface;
pressing a squeezing blade downwardly against the operatively positioned screen with sufficient force to deflect a portion of said tensioned screen engaged by said blade down-wardly into contact with said surface;
translating the downwardly pressed squeezing blade across said screen whereby said amounts of adhesive resin in said pervious printing areas are squeezed therefrom and adhered to underlying respective areas of said surface;
moving said blade away from the operatively positioned screen to permit the tension of the latter to cause said screen to resume its undeflected condition parallel to and spaced up-wardly said predetermined distance from said surface with threads of said adhesive resin initially bridging said distance between said printing areas of the screen and said underlying areas of the surface;
continuing to hold said screen in said operative po-sition parallel to and spaced said predetermined distance from said surface as said resin threads break and fall back substan-tially vertically into the respective ones of said underlying areas; and removing said screen from said operative position only after all of said resin threads have broken and fallen back into said respective underlying areas for ensuring that the margins of the latter are sharply defined.
2. Apparatus for applying a desired pattern of adhesive resin to a substantially horizontal plane surface comprising:
a screen having pervious printing areas in said pat-tern;
a frame across which said screen is stretched;
means for pivoting said frame between first and second positions;
said first position being effective to normally dis-pose said screen parallel to, and spaced from, said surface;
said second position being effective to dispose said screen a substantial distance away from said surface;
a scraping blade;
means for contacting said scraping blade with said screen across a first dimension of the latter;
means for translating said scraping blade in contact with said screen across a second dimension of said screen where-by an amount of said adhesive resin is scraped into said per-vious printing areas;
a squeezing blade;
means, effective when said frame is in said first position, for pressing said squeezing blade against said screen across a first dimension of said screen with sufficient force to deflect a portion of said screen contacted by said squeezing blade into contact with said surface;
means for translating said squeezing blade in contact with said screen across a second dimension of said screen whereby said adhesive resin in said pervious printing areas is squeezed from the latter and deposited in respective areas on said surface;
means for moving said squeezing blade out of contact with said screen while said frame remains in said first position;
and means for holding said frame in said first position for a sufficient time after actuation of said means for moving the squeezing blade to permit resin threads bridging between said screen and the deposited areas on said surface to break and fall back into the respective deposited areas.
a screen having pervious printing areas in said pat-tern;
a frame across which said screen is stretched;
means for pivoting said frame between first and second positions;
said first position being effective to normally dis-pose said screen parallel to, and spaced from, said surface;
said second position being effective to dispose said screen a substantial distance away from said surface;
a scraping blade;
means for contacting said scraping blade with said screen across a first dimension of the latter;
means for translating said scraping blade in contact with said screen across a second dimension of said screen where-by an amount of said adhesive resin is scraped into said per-vious printing areas;
a squeezing blade;
means, effective when said frame is in said first position, for pressing said squeezing blade against said screen across a first dimension of said screen with sufficient force to deflect a portion of said screen contacted by said squeezing blade into contact with said surface;
means for translating said squeezing blade in contact with said screen across a second dimension of said screen whereby said adhesive resin in said pervious printing areas is squeezed from the latter and deposited in respective areas on said surface;
means for moving said squeezing blade out of contact with said screen while said frame remains in said first position;
and means for holding said frame in said first position for a sufficient time after actuation of said means for moving the squeezing blade to permit resin threads bridging between said screen and the deposited areas on said surface to break and fall back into the respective deposited areas.
3. A method of applying a desired pattern of adhesive resin on a substantially horizontal planar surface using a screen having pervious printing areas arranged in said pattern compris-ing:
scraping said adhesive resin over said screen to scrape said adhesive resin into said pervious printing areas;
holding said screen parallel to and spaced a predeter-mined distance from said surface;
pressing a squeezing blade against said screen with sufficient force to deflect a portion of said screen engaged by said blade into contact with said surface;
translating said blade across said screen whereby said adhesive resin in said pervious printing areas is squeezed therefrom and adhered to underlying respective areas of said surface;
moving said blade away from said screen to permit said screen to resume its undeflected condition parallel to and spaced said predetermined distance from said surface; and continuing to hold said screen parallel to and spaced said predetermined distance from said surface until resin threads bridging between said printing areas of said screen and said underlying areas of the surface break and fall back into said underlying areas.
scraping said adhesive resin over said screen to scrape said adhesive resin into said pervious printing areas;
holding said screen parallel to and spaced a predeter-mined distance from said surface;
pressing a squeezing blade against said screen with sufficient force to deflect a portion of said screen engaged by said blade into contact with said surface;
translating said blade across said screen whereby said adhesive resin in said pervious printing areas is squeezed therefrom and adhered to underlying respective areas of said surface;
moving said blade away from said screen to permit said screen to resume its undeflected condition parallel to and spaced said predetermined distance from said surface; and continuing to hold said screen parallel to and spaced said predetermined distance from said surface until resin threads bridging between said printing areas of said screen and said underlying areas of the surface break and fall back into said underlying areas.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP55430/79 | 1979-05-07 | ||
| JP5543079A JPS55148484A (en) | 1979-05-07 | 1979-05-07 | Device for coating resin on printed board |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1137650A true CA1137650A (en) | 1982-12-14 |
Family
ID=12998361
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000350330A Expired CA1137650A (en) | 1979-05-07 | 1980-04-22 | Method for applying adhesive resin on a circuit board |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS55148484A (en) |
| CA (1) | CA1137650A (en) |
| DE (1) | DE3017492A1 (en) |
| FR (1) | FR2456458A1 (en) |
| GB (1) | GB2048780A (en) |
| NL (1) | NL8002616A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3738039A1 (en) * | 1987-11-09 | 1989-05-18 | Thieme Werner Gmbh & Co | SCREEN PRINTING MACHINE |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB821152A (en) * | 1956-10-29 | 1959-09-30 | Mccorquodale Colour Display | Improvements in and relating to apparatus for the deposition of viscous liquid materials |
| FR1472809A (en) * | 1966-03-29 | 1967-03-10 | Automatic inking-dosing device for screen printing machines | |
| US3859917A (en) * | 1972-10-24 | 1975-01-14 | American Screen Printing | Screen printing press |
| US3828671A (en) * | 1972-11-16 | 1974-08-13 | Medalist Ind Inc | Squeegee and flood bar actuator with peeling screen clamp |
| SE398076B (en) * | 1976-09-28 | 1977-12-05 | Svecia Silkscreen Maskiner Ab | STENCIL PRINTING MACHINE |
-
1979
- 1979-05-07 JP JP5543079A patent/JPS55148484A/en active Pending
-
1980
- 1980-04-22 CA CA000350330A patent/CA1137650A/en not_active Expired
- 1980-05-02 GB GB8014586A patent/GB2048780A/en not_active Withdrawn
- 1980-05-07 NL NL8002616A patent/NL8002616A/en not_active Application Discontinuation
- 1980-05-07 FR FR8010219A patent/FR2456458A1/en active Pending
- 1980-05-07 DE DE19803017492 patent/DE3017492A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| NL8002616A (en) | 1980-11-11 |
| FR2456458A1 (en) | 1980-12-05 |
| DE3017492A1 (en) | 1980-11-13 |
| GB2048780A (en) | 1980-12-17 |
| JPS55148484A (en) | 1980-11-19 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |