CA1203971A - Device for fusion of electrodeposited coatings of printed-circuit boards - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

There is proposed a device for fusion of electro-deposited coatings of printed-circuit boards, comprising a means to impart a desired direction to the flow of a heat-transfer agent, and a mechanism for traversing the boards being handled. According to the invention, said means to impart a desired direction to the flow of the heat-transfer agent is made as a chamber having an inlet and an outlet for the heat-transfer agent to come in and come out, respectively, and openings for the boards to pass across the direction of flow of the heat-transfer agent, while the traversing mechanism is accommodated inside the chamber.

Description

The present inven-tlon rela-tes generally to pro-duct-ion techniques of radio-enyineering equ-ipment, and more specifically to clevices for Fus;on oF electrodeposited coatings oF printed-circui-t boards.

The inven-tion can find most utility when applied for fusion of electrodeposited coa-tings on printed-circuit boards used in radio-engineering circuits. In addition, the invention is appicable For fusion of electroplating on flat structural components of equipment subject to soldering during subsequent assembling.

Known in the present state of the art is a device for fusion electrodeposited coatings of boards, comprising a bath with a heat-transfer agent, a mechanisln for establish-ing a flow of the heat-transfer agent, a means for impar-ting a desired direction to the flow of the heat-transfer agent, and a mechanisln for traversing the boards being handled through said means.

The means for imparting a desired direction to the flow of the heat-transfer agent is made as a pair of inter-communicating pipings arranged horizontally one above the other and having the heat-transfer agen-t outlet fittings facing each other.

The mechanism for establishing a flow of the heat-transfer agent in the bath is essentially a pump wi-th an - l -Pi 7~..

impeller and a drive electric raotor4 Toe mechanism or traversing the boards being handl-ed is made as a screen conveyer having stops for the boy ards being haudled, tne top (carrying) strand of the coy-veer passing between said pipin~s~ while its bottom ore-turn) strand runs underneath the bath.
he board on which the electroplating is to be Gus-ed is put onto the conveyer, havi~ preliminarily adJusted the stops thereon to suit the len~tn ol toe board being handled. Whey carried by the conveyer the board is trans-ferred into the zone ox action ox the heat-transfer age~tj hich is pumped from the bath into the piping nile leav-ing the outlet ~ittin~,~s the heat-trans.fer agent preheat-ed in the batn, i5 splashed over toe top and bottom board surfaces as along the direction ox the board run on the conveyer, thus fusing tne elec-troplatin~ on the board.
However7 the construction ox the device descxibed above f ails to provide high-quality fusion, inasmuc~l as it cannot stabilize the time-dependent temperature cha-racteristics of the heat-tra~s~er agent involved in treat-met ol boardsc Splashing ox the heat-trans~er agent over the board surface d~rin~ the board treatment results in rapid cool-in of the heat-transfer agent so that the operation ox the device it to be stopped prom time to time or the heat-transfer agent to acquire a preset temperature in the bath.
In the course ox operation the~h~at-trans~er agent is liable to be vigorously oxidized by tne atMospheric ox-gent while the crystalliæation process is not stabilizeddue to the tact that the construction of tAe device fails to prevent the heat-trans~er agent from ru~ni~g onto the already treated board.
In addition, to proceed to handling the boards of nother type~and size also involves stoppirlg of the device for readjustment of the stops on the conveyer.
Apart prom the disadvan-tages mentioned above the construction of the device is not suitable for fusing fle-xible boards without additional tires or ~tn2ir hold-in in position during treatment nor is i-t capable of pro-cessin~, differently shaped and sized boards or a single technological cycleD
It is therefore a primary and essential object ox the presen-t invention to provide a device or fusion ox electrodeposited coatings of printed-circuit boards, which wound be capable ox attaining high-qualit~ fusion of elect roplating of such boards featuring di~fererlt coy nation and thickness.
Said and other objects of the invention are accom-plished by the provision ox a device fOI' fusion of elect-rodeposited coatings ox pri~ted-circuit boards, comprising a bath containing a heat-trans~er agent a-~ecAa m sm or establishing a flor/ oi' the heat~trans~er agent in the bath, a means for imparting a desired direction to the flow of the heat-trans~er agent, and a mechanism for tra-versirlg the boaxds through said means, wherein accordi~
to the inventiGn, the means or impartirlg a desired direc-'7 tion to the flow ox the heat-transfer agent is made es~
sentially as a closed chamber having an islet and an out-let fitting for the heat-transfer agent to come in and come out, and openings for the boards to pass, said open-its being made in the opposite chamber wall and being axranged square with the direction of flow of the heat-transfer cent and the mechanism for traversin~r the boy ards is accommodated in the above-mentio~ed cha~ber~
Hi~n-quality fusion of the electroplating of the boArds being treated, ire., obtaining of a bright, uni-form, solid coating of a poreless structure is attained due to optimum time-dependent temperature parameters of the heat-transfer agent established in the closed chamb-er and simultaneous treatment of both sides of the pla-te being handled vith the heat-transfer agent under constant and vigorous recirculation, as well as due to continuously equalized tempera-ture of the heat-transfer agent trough-out the volume ox the chamber attained thanks to the fact that the mechanism or traversing the boards under proces-sing is accommodated inside the cna~ber in a continuous slow of the ~eat-trans~er agentO
Minimized running of the heat-trans~er agent onto the board while the latter is entering the chamher and is disc~argi~g there~ro~ is accounted or by the tact that the direction of the board traverse through the cham-ber is square with the direction ox slow ox the heat-transfer agent into the chamber. 'this rules out an ther-. ~5 t7~

mal effect ox the heat-transfer agent on tne already treated board f thus stabilizing the crystallization pro-cess ox the electroplating thereon.
It is expedient tha-t the board traversing mecha-nism be made as rolls arranged in pairs one above the other, the bottom rolls being the driveLl ones to impart transYerse potion to the boards across the flow ox t-he heat-transfer agent, tile tile top rolls are vertically traversable to establish a gap Por tne dif~erent--thick-ness boards to pass in between the rolls Such a constructional arrangement ox the board tra-versing mechanism makes it possible to elect continuous equalization oP the tempexature ox the heat-tra~s~er agent thro~,hout the volume of tile chamber, Poras~uch as the row of the mechanism are situated in a continuous flow of the heat-trallsfer agent and serve as heat accumulators.
I~J~oxeover3 the a~ore~described construction ox the ~echa-nism enables flexible boards to be fused without holding them in position during tra~ersingO
Stabilized temperature conditions ox tne fusion chamber are attained also due to the fact that the zone of thermal eject on the chamber is confined witlin the first and last rolls as along the direction ox run ox the board being processedD
It is also gavo~able that vertical slot e--mad~
in the ~ppo~ite walls of the chamber to receive the sha~t~
oP the top rolls with a possibility or tne rolls to rotate and traverse vertically. This wakes it possible -to process 3l~'7~

different-~hick.~ess boards for a single cycle witnou'G
additionel readjustment ox the board traversing mecha-nism.
It is likewise practicable that -the top rolls be made sectionalized, i.e., composed of a plurality of dis'~s vertically traversable ~Jlth respect to one another or the different-width boards to pass. suet a construction of' the top rolls prevents the heat-transfer agent Lrom flo~in~ out of tlle chamber when hank the boards that are much narroi.JJer tnan the openings f'or t~leir passing he disks form.ing the top rolls are reasonable to be set loosely on the snaI`ts ox said rolls. This provides for.
a possibility ox treating the boards ox different tllick-ness, width and shape or a sidle technological cycle without vertical readjustment ox the top rolls, since the disks constitutinO these rolls are raised only v~hen inter-acting with the boards being handled so that the amount ox the gap betuveen the shafts of the top rolls and the in-side diameter of the disk should correspond to the maxi-mal thickness ox the board being handled.
Furthermore, it is advantageous that the openings in the chamber walls or the boards to pass lie in a plane passing through the line of' contact of the rolls with each other O
Such an arran&-ement of the openings mazes it pos-sible to dispense with holding ox the boards to the con-veyer during their processing the fusion chamber, singe 3'7~

the board being handled rests, irrespective of its tll.ick-ness~ upon the bottom rolls 9 nigh cannot traverse vertic--ally and assume a strictly fixed position with respect to the openings in the chamber Jells In ~r~hat follows the present invention will be il-lustrated by a detailed description of a specific embodi-met thereof with reference to the accompanying drawings, in ~ihicn:
FIG. 1 is a general schematic cross-sectional vieu ox a device for fusion of electrode~osited coatings of printed-circuit hoards, according to the invention;
IG. 2 is a section taken along the line II-II of FIG. l;
IG. 3 is a general scaled-up pelspective vie~v of a means for imparting a desired direction to the slow of a heat-transfer agent, made as a closed chamber, accord-ing to the invention and IG. 4 is a section taken along the line IV-IV of FIG. 3 -to illustrate the uni.t of interaction of the top roll made up of disks, with the bottom roll and the board being handled.
he device or fusion of elec..rodeposited coa-tings of printed-circuit boards comprises a bath 1 (FIG 1) con-tainlng a heat-transfer agent 2 and a heater element 3.
the device has also a mechanism 4 (Fig. 21 for establish-ing a flow of the heat-trans~er agent in the bath {said flow being indicated with the arrows 'a' it IS 2 and 3).

D3i'3'7~

The mechanism 4 is made up of a electr.ic motor 5 and on impeller 6. In addition, the proposed device comprises a means 7 IS 1., 2) or i~lparting a desired direction to tL~e slow ox the heat-trans~er agent; and a mechanist for carr~in~ the boards through said means 7.
The means for imparting a desired direction to the flow of the heat-transfer agent is made as a chamber 8 closed on every side andhaving an inlet 9 and an outlet 10 or the heat-transfer agent to come in and come out, respectively, and openings 13 made in the opposite falls 11, 12 (JIGS 1, 3) OI' the chamber 8 and arranged across the direction ox flow ol' the heat-trans~er aOent, for boy ards being handled to pass, e.g. ? a printed-circuit board 14 (FIGS 3, 4).
he board traversing mechanism is accommodated in-side the chamber 8 and incorporates bottom rolls 15 and -top rolls 16 arranged in pairs owe above the other.
The bot-tom rolls 15 are driven prom a sprocket 17, which imparts rotation via a shalt 18 to gear wheels l 20, 21, 22, 2~ 2~, 25, 267 27 rigidly secured on the bot-tom rolls 15~ Rotation to the sprocket 17 is imparted by a chain drive jot shown).
The top rolls 16 are vertically traversable to es-tablis~-~ gap or the di~erent~thickness boards 14 to pass it between the rolls 15 and 16. this is made possible due to the fact that vertical slows ~0 aIe provided in opposite walls 28 (FIG. I) and ~9 o toe chamber 8 -to re-_g_ ceive shafts 31 o the -top rolls 16 so as to render toe latter rolls rotatably and vertically traversable.
The opening 13 in the walls OL' the chamber lie in a plane passing, through the line old contact ox the rolls 15 and 16 ~vith each other. Provided at the inlet and outlet openings 13 are respectively a conveyer 32 (JIG. 1) to feed the boards 14 into the cilamber 8 and a conveyer 33 to discharge tLle boards 14 from the cnamber 8.
Each of the top rolls 16 is sectionalized (FIG. 4) atld made up of a plurality of disks 34 set on the shaft 31 with a clearance 35 so as to alto the disks 34 to traverse vertically with respect to one anotner or the different width board 14 to pass.
he device ol the invention operates as follows.
he beiQorehand llux-coated printed-circuit board 14 is put on the feed conveyer 32, v~Llich transfers the Doard 14 to the inlet opening l ox the c~a~ber 8. ye board 14 is caught by the~airs of the rotary rolls 15 and 16pwhich draw the board to the next pair of tl;e rollsO The top rolls 16 are raised along the slots 30 in the walls 28, 29 or distance equal to the thickness ox the board 14.
The first top roll 16 as in the direction ox board travel9 lies do onto toe board surface, thus preventing the heat-trans~er cot 2 prom running onto the board por-tion that still remains ~eyo~d toe chamber 80 he heat-transiQer agent 2 continuously xecirculat-i~g in the chamber 8, flows by the board 14 uni~Qorm~y and ~J~ '7~.

simultaneously on its every side vihen the board is tra versing between the rolls 15 and 16. The temperature fi-eld viithirl the cha~lber 8 is uniform through the entire volume thereof, since tne heat-transfer agent is recir culating constantly inside the chamber and tne contact OL the heat--transfer agent ilk the atmospheric is mini-mized. Besides 9 as the rO11S 15 and 16 are continuously situated in the 30~e o F action ox -ths heat-transfer agent

2, they serve as heat accumulators to equalize the tempe-rature thereon.
The rolls 15 and l carry the board 14 through a con-tinuous flow of the heat-trans~er agent 2 across the di-rection OL motion of the latter and bring the board 14 outwards onto the board discharge conveyer 33. Once the board 14 has been withdrawn prom the chamber 8 the last top roll 16 (as in the direction of the board travel mo-ves down o~-to the roll 15, thus closing the opening 13 and preventing the heat-trans~er agent 2 prom running on to tne already processed board 14. This stabilizes the process of crystallization ox the used electroplate coat-ing.
The slow ~a9 o:' toe heat-transfer agent 2~ ou pass-in through the chamber 8, returns to tne bath 1 via the outlet 10~
Jihen no boards 14 are present in the chamber 8, the ex;re~e rolls 15 and 16 are in an intimate contact wi-th each other and the heat~trans~er agent is practically prevented lDrom Flowing out through the openings 13~ as the flow 'a of the heat-transfer ag-ent 2 moves along the .rolls 15 and 16 in tile cha~,lber 8.
then trea-ted in the chamber 8 is tne boa.rd 14 ~IG.4), which is much narrower than the opening 13, the disks 34 on the stationary fixed shalt 31 are raised above toe board 14 due to the clearance 35, while the disks 34 not in contact with the board 14 being handled remain tightly pressed against the bottom roll 15 by its O~J~ mass. This also contributes to preYenting the flo~iin~ of the heat-transfer agent out of the chamber 8.
he device for .L usion of electrodeposited coatings ox prin~ed-circuit boards is in fact the one featuring en-tended functional capabilities, inasmucn as it .is it the first time in the engineering practice that there is pro-vided high-qualit~ fusion ox multi- and single-layer prin-ted-circuit boards of low thicknesses ~0.1 to 0~ mm), in-cluding flexible boards, of any length and configuration.
Apart from that the device features high output as it operates on a continuous cycle due to ruled out stopp~
in- or readjustment an equalization ox the heat-trans-per agent.

Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A device for fusion of electrodeposited coatings on printed circuit boards, comprising a receptacle containing a heat transfer medium; means for conveying flow of the heat transfer medium out of said receptacle; means for imparting a desired flow direction to the heat transfer medium, compris-ing a chamber provided with first inlet and outlet openings for the heat transfer medium to pass through said chamber in the desired flow direction, and further provided with second inlet and outlet openings for the boards to pass through said chamber, said first and second openings situated to define substantially transverse directions of passage to the heat transfer medium and of the boards through said chamber; and means for conveying the boards through said chamber, compri-sing cooperatively acting top and bottom roll means, said bottom roll means comprising means for conveying the boards substantially transversely relative to the direction of heat transfer medium flow, and said top roll means mounted for movement in a direction substantially vertically, to allow boards of different thicknesses to pass between said respec-tive top and bottom roll means.

2. The device of claim 2, wherein opposite walls of said chamber are provided with vertical slots to receive axes of said top roll means for rotational and vertical move-ment thereof.

3. The device of claim 2, wherein said top roll means comprises a plurality of roll discs mounted for rota-tional and vertical movement to prevent leakage of the heat transfer medium from said chamber when boards of varying thicknesses pass therethrough.

4. The device of claim 3, wherein said discs defin-ing said top roll means are loosely mounted on the axes of said roll means.

5. The device of claim 4, wherein clearances are provided between respective axes and discs.

6. The device of claim 1, wherein said second openings lie in a plane passing through a line of contact of said top roll means and said bottom roll means.