GB2225663A

GB2225663A - Training or monitoring printed circuit board techniques

Info

Publication number: GB2225663A
Application number: GB8926492A
Authority: GB
Inventors: William J Siegel; Louis A Abbagnaro; William J Kautter
Original assignee: Pace Inc
Current assignee: Pace Inc
Priority date: 1988-11-23
Filing date: 1989-11-23
Publication date: 1990-06-06
Anticipated expiration: 2009-11-23
Also published as: DE3938847A1; FR2646313A1; GB2225663B; GB8926492D0; CA2003202A1; IT8922500A0; IT1236825B; JPH02211489A; IT8922500A1

Description

1 k 1 1,._ - 1.

-,Docket No. 239-382 PRINTED CIRCUIT THERMOCOUPLE-ARRANGEMENTS.F.OR PERSONNEL TRAINING AND EQUIPMENT EVALUATION PURPOSES, AND METHODS FOR MAKING AND USING SAME Back,ciround of the Invenion The present invention relates to thermocouples which are used in conjunction with printed circuit boards f or training personnel in solde ring/de soldering of leads of circuit components to the printed circuit boards, as well as for conducting a quantitative analysis of the performance of repair, rework, and production equipment used for s olde ring/de soldering, cleaning, preheating, and spot-welding of components mounted to printed circuit boards. In particular, the invention relates to the formation of thermocouples for such purposes by standard printed circuit board construction techniques, as opposed to standard thermocouple construction techniques, as well as the manner in which they can be made and used to emulate a wide variety of circuit board types, layouts and assembly configurations.

TrI commonly owned U.K. Patent: No. 1,600,753, circuitry for teaching soldering and a practice circuit board for use therewith are disclosed, wherein a training board having a plurality of terminals thereon and wherein a plurality of temperature sensing devices associated with the respective terminals are provided at each terminal where the soldering of a joint is attempted to monitor the performance of a trainee or other person whose repair skills are being evaluated. One form of temperature sensing means that is disclosed Js the provislon of thermocouples at each of a 1 ,plurality of through holes formed in a printed circuit ,_,board. These thermocouples are comprised of a first conductor, such as electroless copper, that is plated through the holes so as to form pads or lands at each of opposite sides of the printed circuit board, and a metal foil or wire made of iron or constantan or some other dissimilar conductor metal from that of the plated through hole that is attached to one of the pads or lands of the plated through conductor, whereby a thermocouple junction is formed. For formation of these thermocouple junctions, the use of electrical arc, flame heating, soldering, swagging, welding, brazing, beading, or butt-welding techniques are disclosed- Furthermore, while this patent indicates that its disclosure is also applicable to desoldering, welding, etc., as well as to circuit connections other than those on a single or double-sided printed circuit board, such as multilayer boards, ceramic printed circuits, etc., and various terminations such as platdd through holes, unsupported holes, funnelets, eyelets, standoffs, etc., no structures, technic-rues or aDDlicat-ions are disclosed which are either directed to the emulation of a wide assortment of circuit board layouts, types and assembly configurations which vary by component type, substrate material, thermal characteristics and other factors, or to the aDDlication thereof to the development, evaluation, mon-itorincr and adjustment of "thermally affecting" production, rework or repair processes and equipment used there-for, i.e., for soldering/desoldering, preheating, spot-welding, etc.

Commonly owned U.K. Patent No. 1,600,753 discloses in detail the various factors which impact upon the ability to perform high quality rework and repair operations upon electronic assemblies, and this descriotion is hereby incorporated by reference for the sake of brevity. These factors include not only the human factor, for which training to obtain the requisite skills and experience to enable the operator to observe the work and react appropriately in the manipulation of the soldering iron or other rework and repair device is the best insurance. but also includes other factors which are not operator dependent, such as the characteristics of the rework and repair device, e.g., a soldering iron for which its idle tip temperature, recovery rate, etc., and characteristics of the component and printed circuit board, such as temperature, thermal conductivity, specific heat, etc. As a result, for proper training and evaluation of personnel, it is desirable to be able to simulate as realistically as possible a wide range of circumstances an operator is likely to encounter. Also, even with the best of training, the potential exists for overheating the work, as a result of excessive dwell times or temperatures, so as to cause printed circuit board damage in the form of lifted pads, damage to plated through holes, or, in extreme cases, damage to the fiberglass laminate, etc., as a result of equipment related factors. Thus, it is also desirable to provide a means by which new equipment can be evaluated, particularly automatic equipment, through analysis of i le that, for example, a soldered the temperature profjoint is exposed to during, for example, a solder- ing/desoldering process.

The normal method of soldered joint inspection is visual. However, such a qualitative method of analysis is ineffective since the physical appearance of a soldered joint, after it has been made, gives no real indication of the maximum temperature that the joint achieved or how long it was maintained at that temperature. on the other hand, to obtain a quantitative analysis of the temperature conditions to which a joint is subjected, thermocouples have to beattached to the circuit pads and/or component leads, so that temperatures can be recgrded utilizing a computer data logging system. However, attaching thermocouples to leads or pads, usually done by spot welding, is a difficult task, and if multiple joints are to be analyzed, the task becomes cumbersome and expensive as each thermocouple costs approximately $5.

Summary of the Invention

It is an object of the present invention to provide a thermocouple construction and process which will enable a wide assortment of printed circuit board types, layouts and assembly configurations, varying in component type, substrate material, thermal characteristics and other factors, to be simply and inexpensively emulated.

A particular object of the invention is to adapt standard printed circuit board construction techniques to the preceding object.

Another important object is -to provide processes whereby a thermocouple construction in accordance with the invention may be employed in the development, evaluation, monitoring and adjustment of thermally affecting processes, processing equipment and human factors associated therewith.

it is a further object of the present invention to enable the quantitative analysis of temperature profiles that will be produced in emulated printed circuit board assemblies during performance of an actual thermally affecting production, rework and repair process, such as soldering, desoldering, cleaning, fluxing, preheating, thermocomnression bonding, spot welding and other processes which can thermally affect such assemblies for purposes of b 11 evaluating the process and processing equipment and for training or recertifying of repair personnel, via measurement of the temperature experienced by solder joints, component leads, and/or substrate material of a printed circuit board assembly in a test process operation.

The foregoing objects of the invention are achieved in accordance with various embodiments wherein a layer of a first conductor material, such as copper, is applied on a first surface of an electrically insulative support, while a second layer of a second, dissimilar, conductor material, such as constantan, is applied to at least one other surface of the support using conventional printed circuit board construction techniques, as opposed to standard thermocouple construction techniques. At those locations where thermocouple junctions are required, holes are drilled through the conductor layers and support material, and then the two layers of conductor are elecrically connected by a plating of the first conductor material through the through hole and onto respective pad terminal portions of the conductor layers. The voltages produced by the thermocouples during a production/repair/rework operation on an emulated electronic assembly may be monitored and used to develop,modify or adjust the operation of-thermally affecting processes thereon, train personnel or evaluate equipment. Numerous different processes can be evaluated involving different permutations of thermal mass configurations, heat source locations and types, and thermocouple locations.

In accordance with one aspect of the present invention there is provided a thermocouple arrangement for providing temperature data, resulting from use of at least one thermally affecting process on an electronic assembly via an emulated production/rework/repair operation, comprising an electrically insulative support, a layer of a first conductor material applied-on a first 5a --1\ surface of said support, at least one printed circuit pattern of a second conductor material, that is dissimilar to said first conductor material, formed on at least oneother surface of the support; wherein said printed circuit pattern is comprised of circuitry having thermocouple pad terminal portions, signal monitoring connection portions and trace interconnections running therebetween; wherein at least one thermocouple pad terminal portion of the printed circuit pattern of the second conductor is connected to the layer of the first conductor material by an electrical connection that is formed of said first conductor material and which extends through said support therebetween in a manner creating a thermocouple junction on the respective thermocouple pad terminal portion.

In accordance with another aspect of the present invention there is provided a method of making a thermocouple arrangement for providing temperature data resulting from use of a thermally affecting process on an electronic assembly via and emulated production/reworklrepair operation, comprising the steps of:

(A) applying a layer of a first conductor material on a first surface of an electrically insulative support; (B) forming at least one printed circuit pattern of a second conductor material, that is dissimilar to said first conductor material, on at least one other surface of the support, said pattern being comprised of circuitry having thermocouple pad terminal portions, signal monitoring connection portions and trace interconnections running therebetween; and (C) connecting at least one thermocouple pad terminal portion of the printed circuit pattern of the second conductor to the layer of the first conductor material by forming an electrical connection of said first conductor material which extends through the support from said layer of first conductor material to the thermocouple pad - 5b - terminal portion of the circuitry in a manner creating a thermocouple junction thereon.

In accordance with a third aspect of the present invention there is provided a method of obtaining temperature data pertaining to the performance of a thermally affecting process on an electronic assembly by the emulating of a production/reworklrepair operation, comprising the steps of:

(A) emulating an electronic assembly by providing a thermocouple arrangement, comprising an electrically insulative support, a layer of a first conductor material applied on a first surface of said support, at least one printed circuit pattern of a second conductor material, that is dissimilar to said first conductor material, formed on at least one other surface of the support; wherein said printed circuit pattern is comprised of circuitry having thermocouple pad terminal portions, signal monitoring connection portions and trace interconnections running therebetween; wherein at least one thermocouple pad terminal portion of the printed circuit pattern of the second conductor is connected to the layer of the first conductor material by an electrical connection that is formed of said first conductor material and which extends through said support therebetween in a manner creating a thermocouple junction on the respective thermocouple pad terminal portion, so that leads of the electronic component are disposed on respective thermocouple pad terminal portions of said printed circuit pattern; (B) emulating a production/rework/repair operation during which a thermally affecting process is actually performed with respect to said thermocouple arrangement; (C) producing an electrical signal, representative of temperature data pertaining to the effects of at least said thermally affecting process of the - 5c I production/reworklrepair operation emulated, via at least one said thermocouple junction; and (D) generating an output from said electrical signals by which said effects can be evaluated.

In accordance with a further aspect of the present invention there is provided a printed circuit thermocouple comprising an electrically insulative support, a first conductor material applied on a first surface of said support, a printed circuit pattern of a second conductor material that is dissimilar to said first conductor material, formed on at least one other surface of the support, said printed circuit pattern being comprised of circuitry having at least one thermocouple pad terminal portion, signal monitoring connection portion, and trace interconnection running therebetween; wherein the at least one thermocouple pad terminal portion of the printed circuit pattern of the second conductor is connected to the layer of the first conductor material by an electrical connection that is formed of said first conductor material, and which extends through said support therebetween in a manner creating a thermocouple junction on the respective thermocouple pad terminal portion.

In accordance with another aspect of the present invention there is provided a method of making a printed circuit thermocouple comprising the steps of:

(A) applying a layer of a first conductor material on a first surface of an electrically insulative support; (B) forming at least one printed circuit pattern of a second conductor material, that is dissimilar to said first conductor material, on at least one other surface of the support, said pattern being comprised of circuitry having at least one thermocouple pad terminal portion, signal monitoring connection portion, and trace interconnection running therebetween; and (C) connecting said at least one thermocouple pad terminal portion of the printed circuit pattern of the 5d second conductor to the layer of the first conductor material by forming an electrical connection on said first conductor material which extends through the support from said layer of first conductor material to the thermocouple pad terminal portion of the circuitry in a manner creating a thermocouple junction thereon. - 1 1 Brief Description _Qf--the_DrQiwin!W

Fig. 1 is a partial cross-sectional view of a printed circuit thermocouple construction for a simple circuit board having a through hole mounted component; Fig. 2 illustrates. in cross section. a portion of a printed circuit thermocouple construction for monitoring temperature at both sides of a three layer printed circuit board having a surface mounted component; Fig- 3 illustrates, in cross section, a portion of a printed circuit thermocouple construction for providing a detailed analysis of the temperature gradient of a multilayer printed circuit board; and Figs- 4 through 6 illustrate representative photomask patterns for production of printed circuit thermocouples in accordance with the present invention, Fig. 4 showing a pattern for 16 pin DIP with thermocouple junctions for each lead and eqUal width traces. Fig. 5 also showing a pattern for a 16 pin DIP but with lands of varying size or thermal mass, and Fig. 6 showing a pattern for a surface mount component having a land configuration for producing a complex temperature profile- Detailed Description of the Preferred Embodiments in Fig- 1, a basic thermocouple arrangement for providing temperature data resulting from a test printed circuit board rework. repair. or production operation, involving at least one "thermally affecting process, " is illustrated of a type that might be used for the purpose of training students in the art of soldering in the manner of the above-notedU.D',. Patent 1 %Yo. 1,6.00,753 (which is incorporated by reference), orfor recertifying of experienced repair personnel, or in the evaluating of new reworkand repair equipment. In this regard, it is pointed out that, for purposes of this application, the term "thermally affecting process" is used to define any of the many processes used in the reworking, repairing or producing of electronic assemblies (such as soldering, desoldering, cleaning, fluxing, preheating, thermocompression bonding, spot welding, cooling, and other processes involved in the installation, removal and replacement of through hole or surface mounted components) that can affect the structure, operability and/or appearance of any part of an electronic assembly due to temperature effects. It is also noted that even though the construction of the embodiments of Figs. 1-3 is being described with reference to only a single thermocouple junction of the inventive arrangement, it should be appreciated that a thermocouple arrangement for emulating an electronic assembly (including bare circuit boards and boards in the manufacturing process) in accordance with the present invention will comprise at least as many thermocouple junction sites as the number of leads of the number of components to be utilized in conjunction therewith.

In particular, the printed circuit thermocouple arrangement of Fig. 1 is comprised of an electrically insulative support 1, which may be a standard circuit board substrate formed of glass reinforced epoxy or other suitable material. A layer of a first conductor material, such as copper, is applied on the first surface of the support 1, while a second layer of a second conductor material, that is dissimilar to the first conductor material, such as constantan, is applied to the opposite side of the support 1. These layers of conductor material are formed utilizing conventional printed circuit board construction techniques. For example, a copper foil 3, approximately.002 inches thick is- laminated to one side of the substrate, while a constantan foil 5, of approximately.002 inches thick, is laminated to the other side. At those locations where thermocouple junctions are required, holes are drilled through the foils and substrate laminate and then pad terminal portions, in the form of lands, are defined around the holes on both sides of the support 1, using photomasking techniques. Electroless copper 7 is then plated on the pads, as defined by the photomasked pattern, on both the copper and constantan foils and through the holes. The copper plating 7 electrically and mechanically connects the copper and constantan foils forming a T-type thermocouple junction. Signal monitoring connection portions and trace interconnections running between the signal monitoring portions and the lands are then formed on both foils using photomasking techniques and the unwanted copper and constantan foil is then removed using a suitable etchant, such as ferric chloride, to complete the ciruitry pattern.

As a result of the above steps, a thermocouple junction 9 will be formed at the interface between the respective thermocouple pad terminal portion of the printed circuit pattern of constantan 5 and the platedon copper 7. Thus, in every instance, the constantan conductor material will be formed into an articulated printed circuit pattern. on the other hand, since a copper-to-copper electrical connection is formed at the interface 11 between the copper layer 3 and the platedon copper 7 at the opposite side of the insulative support 1, the layer of copper 3 may either be a matching articulated printed circuit pattern, or where load, thermal isolation or instrument sensitivity - 9 I- - requirements will permit, the c6pper may be left in its- originall sheet form, whereby it will be coextensive in area with at least the are_a - upon- which the printed circuit pattern is formed and can totally cover the respective side of support 1.

Fig. 1 shows the thermocouple arrangement being utilized to obtain data as to the temperature profile at the Doint at which solder S is applied by a soldering tool T, such as a soldering iron, in the through hole mounting of an electronic component 13 having a plurality of leads, of which only the one lead 13a is shown in Fig. 1. Of course, other forms of soldering tools and automated soldering devices can be utilized in conjunction with this thermocouple arrangement, such as wave type soldering devices as are typically used in the mass production of through hole printed circuit boards (in which case the arrangement would be inverted relative to the orientation shown in Fig. i and d-isposed above a molten solder bath of a wave soldering device).

in th i I s regard, it is noted that monitoring ol- the signals ffro.- the thermocouple junction in most cases can be done utilizing a typical pr-Lnt:ed circuit board edge connector or any other conventional type of connecto-r. -;-;owever, in the case where the thermocouple arrance;-.. enz: is disposed above a wave soldering bath, the output connections can only be made to the upper surface of the board. In Fig. 1, a simple voltage meter is merely schematically shown and is only intended to generally represent an output quantifying for use in measuring the temperature related means 4. vcltaQe Droduced by thermocouple junction 9. in addition to soldering operations, desoldering processes can also be evaluated with the described thermocouple arrangement once a componen-L has been mounted thereto. In that case, a solder extractor too! is placed against the solder and around the lead on the side opposite the component body, solder side in the case of --a through hcJ-e The desoldering device is then activated to to the so-1der joint, and once the solder component i.e., the mounting.

apply heat is heated above its melting point, vacuum is applied to remove the solder from the hole. Likewise, any other thermally affecting process can be monitored in a similar fashion.

In the case of the Fig. 1 embodiment, if the comDonenc were to be inserted on the constantan side, the heat necessary to melt the solder in the hole must travel through the copper plating, component lead, and.r- h e solder z s e 1 f. As a result, temDerature measurements taken during the desoldering process will be biased toward the component side of the board since the thermocouple junction would be on that side. For circuitry having small lands and trace portions and small mass component leads, the temperature diffEerential from the solder side to the component side w-J-111 be small. However, if, for example, a large area circuit trace o-land is situated on the comiDonent side, there will exist a finite temperature differentiall between the solder side, where the heat is aDn-i-ied, and the component side where it is sensed via t,-e z--el-mocouD-!e junction 9. This temperature differential is the result of the fact that the heat necessary to ra-.se the temperature of a large circuit area: to scolder melz must flow through the combination of Dlated through hole, component lead and solder, and kh elak-ively low thermal he r-l-.-ough hole r)a has a transfer raise the This 1ow f rorin the impeded.

raze in comparison to the heat required to temperature of the component side circuitry. thermal transfer rate causes the heat flow solder side to the component side to be thereby creating the noted temperature - 11 gradient between the two sides. Thus, under such7 c i _- c umstances, the thermocouple junction 9 must be on the side oJL support 1 that the tem]eratur.e is desired to be monitored at, i.e., the component 13 should be through holle mounted at the side shown in Fig. I or surface mounted at the opposite side (in a manner to be described below with respect to Fig. 2). On the other hand, where circuitry having small lands and circuit trace portions and/or small mass component leads are involved, suitable results will be obtained irresnective of which side of the arrangement of Fig. 1 the component is mounted at.

Fig. 2 illustrates a thermocouple arrangement for monitoring of temerature data via thermocounle heat sensors disposed on each of opposite sides thereof. With such a construction, the electrically support 21 is formed of a plurality of circulit board layers 21a, 21b, and the layer of the first conductor ri-aterfall (e.g., copper) 23 is formed on an interface surface of the support 21 between the pair of board f the,ayers 21a, 21b. Printed circuit patterns ol second conductor material (e.g., constantan) 25a, 25b are t' en --Fcrmed on each of the opposite outer surfaces of zhe insulative support 21, and are electrically and mechanical lly coupled to each other by a plated through eleczrical connection 27, as described above, relative to the conductors 3, 5 and the electrical connection 7. As a result, a pair of thermocouple junctions 29a, 29b occurs at the interfaces between the electrical connect-on 27 and the layers 25a, 25b, while an electri-cal connection 31 is produced at the interface between the first conductor layer 23 and the through hole plating of the electrical connection 27. Whether r-he internal layer of the first conductor 23 is a conzinuous sheet ffolill filling zhe interface between board layers 21a, 21b, as shown, or is an articulated 12 - pattern of traces, the interstices of which are filled ---'with an insulator materialk will be dependent, as notedabove, upon load, thermal isolatio n and sensitivity requirements (which in mogt cases wi-1-1 make the patterning of all conductor layers preferable).

Fig. 2 also shows the surface mounting of an electronic component 33 via its lead 33a. For this purpose, unless the through hole is designed to have a very small diameter, a plug 35 of - first conductor material (e.g., copper) is inserted into the through hole, cr the hole may be f illed or reduced to only a very small diameter by the melting of solder into it. at least at the component mounting side of the arrangement. However, the arrangement of Fig. 2 can also be utilized for through hole mounting in the manner described relative to Fig. 1.

An arrangement as is shown in Fig- 2 is particularly advantageous when evaluating a production, rework or repair process wherein an auxiliary heat source is used with a printed circuit board having a ground plane(s) or other heat sink that makes it for a primary heat source, such as hot air de]-ivered to the component side of Fig. 2, to quickly ra-ise the temperature at the component leads to the solder melt temperature. In such a case, an auxiliary heat source is urillized to offset the undesired heat sink by bringing the board up to a premelt temoerature such as 2500F. For example, if a large thermal mass is located at the bottom side of the board due to a ground plane. the primary heater may be ihcapable of delivering sufficient heat to raise the temperature at the component leads to solder melt temperatures due to a heat sinking by the mass which can be counterbalanced by the use of a preheater at the bottom of 'the board in -er at the top, addizion to using a primary heal component side of the board, relative to Fig. 2. Thus, 1 13 - by utilizing an arrangement as shown in Fig. 2, wherein thermocouple junction tyPesensors are provided at both sides of the board, the effect of the use of combined heaters at both the top and bottom of a Z'lrcuit board being emulated can be evaluated. Alternatively, the effect of only one or the other of the heaters can also be evaluated separately at both the top and bottom surfaces of support 21. These temperatures can be measured by the use of voltmeters, schematically depicted at V, and V2, which measure the voltages produced by the thermocouple junctions 29a, 29b.

To obtain a more detailed analysis of the -emperature prof-Ile, by examining the temperature gradient, any number of additional circuit layers can be added- For example, Fig. 3 illusr-rates a printed circuit thermocouple arrangement in accordance with the wherein the electrically insulative support 41 is subdivided into four circuit board layers 41a41d,at each side of which a conductor layer is formed. in this case, the central conductor laver 43 is formed of a first conductor material, such as copper, while all of the other conductor layers 45a-45d are formed of r.ne second, dissimillar, conductor material, such as -anLan. All of the layers 45a-45d are of an const articulated printed circuit pattern produced as described above, while layer 43 of the first conductor material, while preferably also being so patterned, may, as already pointed out for the other embodiments, be left as a continuous foil layer. The temperature gradient can then be measured by arranging voltmeters Vl_V4 as shown in Fig. 3, for measuring the voltages produced at the thermocouple junctions 49a-49d.

While simple voltage meters are depicted as the means for monitoring the voltages produced at the thermocouple junctions of the embodiments of Figs. 1-3, it should be appreciated that numerous other and more sophisticated means may, be used. For example, analyzers and indicators of the type disclosed in the above- re f erenced U. K, Patent' may be utilized, as can other comparable types of arrangements designed for particular circumstances. Moreover, data is obtainable throughout the entire operation cycle from ambient to ambient, and not merely during perforamce of a specific thermally affecting process of an overall production, rework, or repair operation.

Figs- 4-6 show printed circuit pattern masks for use in forming any of the conductor layers of the printed circuit thermocouple arrangements of Figs. 1-3. Tn Fig. 4, a pattern mask 60 is shown for a 16 pin DIP having thermocouple pad terminal portions 62 for each lead and equal width trace interconnections 64 connecting the thermocouple pad terminal portions 62 with sign=-! monitoring connection portions 66. Of course, it should be appreciated that the portions of -he mask 60 that are not within the positioni-ng frame corners 68, including the corner frames 68, would be removed by an etchant, as noted above relative to the process of making the thermocouple arrangements of the --resent -invention.

In Fic. 5, a nattern mask 70 for a 16 nin DIP is However, in this case, the thermocouple Dad zerminal port-Lons that are monitore v-a trace interconnec-L.ions 74 and connection portions 76 provide a graduated circuit area ranging-from terminal portions 72a, formed of lands of a small area/mass and comparable to those of Fig. 4. up to terminal portions 72b, whic-hi are formed as lands that have a large area/mass. Since an increased circuit area produces greater thermal loading, increased circuit areas will lengthen the time it takes to heat a solder joint there-;=t71"hus, a pattern as shown in Fig. 5 can be utili zed -to emulate a circuit board having wide- traces also S-1-own.. - Z d J - is - or a ground plane attached to the pad. It is noted, that, in addition to this technique, other techniques can be used to simulate ground planes (or other heat sinks) on or in a printed circuit board which may be a single layer or multilayer board. For example, with reference to Fig. 3, the diameter of the through hole can be varied and/or the thickness of the hole wall plating 47 can be varied. As a result, electronic Jes and processes resulting in complex assembil temperature profiles can be emulated. For examDle, r many of the thermal characteristics OIL multilayer printed ci.rcuit boards may be emulated by a much less 4ve double-sided board made according to the exnens' present invention.

Fig. 6 shows a pattern surface mount component having but with terminal oortions 82a mask 80 for a large, 17 leads on each side for forming thermocouple junctions at only three spaced locations at each side (such as at the third, eighth and f - ifteenth lead), as well as terminal portions 82b spaced 0.2 inches away from the center of the row of terminal portions 82 at ea ch s _J d e. Such an arrangement allows a complex " e n r o f i.L 0-1 teimperatures of the comoonent and z, L :rrouzriding area to be obtained during various or.-Cesses. _Tn this regard, while only 16 thermocouples are shown in Fig. 6 (or for that matter in Figs. 4 and 5 as well), the number of thermocouples is limited only bv the amount of space available and the interconnection canabilities via the lead traces 84 and monitoring connection portions 86. Furthermore, the use of zhermocouple arrangements of the type shown in Fig. 6 is particularly advantageous with regard to the evaluation of densely populated board assemblies to determine the thermal effects transferred to components that are not being directly operated on and can involve monitoring of thermocouple junctions of adjacent patterns, not only those junctions of the pattern pertaining to the component that is being directly subjected to a thermally affectJLng- process during a particular emulation.

it should also be appreciated, from the foregoing, that various permutations of (a) thermal mass conf -igu.-ations, (b) heat source locations, and (c) thermocoup'e junction location can be created, in accordance with the present invention, so as to be able Lo enulate a wide assortment of printed circuit board siZes, tvnes, layouts and assembly configurations as as to evaluate a wide variety of qe I - solder ing/de soldering processes, or other types of production, repair or rework operations requiring the anolicarion of heat to a printed circuit board arrangement.

Furthermore, while the printed circuit board thermocouple arrangements in accordance with the uresent invention have all been described relative to a--rangements wherein the thermocouple junctions are formed on an electrically insulative support that si.n...Lul-a-tes 1--.--).e effect experienced at various locations on differenz types of printed circuit boards, it should be aooreciazed 'chat due to the use of conventional orinred circuit techniques to create the thermocouples, other r)css-;bJl'--Jt-Jes exist. For example, the printed c'; -- it u tlermocounles could be -formed within a si.mulazed ch-iip, wherein the number of printed circuit th.ermocoup-les corresponds to the number of chip leads.

A!--ernativel-y, the number of printed circuit thermocouples formed on the chip substrate, serving as the electrically insulative support, could be less than -he number of chip leads, whereby some of the chip leads may be connected to a heat source and others to an output analyzer. In this way, temperature data pertaining to a production, repair or rework operation being performed on a printed circuit board can bp, obtained in a manner reflecting the heat effects which are directly experienced by -an electronic component itself, thereby further expanding upon the ability to train personnel, to develop, adjust and monitor any thermally affecting process, such as soldering, and to evaluate process equipment in accordance with the present invention using, for example, an analyzer that can store time and temperature curves, as described in he referenced U-!, - Patent No. 1. 600, 753 1 also Those of ordinary skill in the art wi.

recognize that the materials described as examples for use in conszruction of the present invention represent only one possibility for which many substitutes are available. For example, instead of using a support formed of a glass reinforced epoxy circuit board substrate, ceramic, or polyimide aminates may be used. Furthermore, instead of forming T w-type thermocouple junctions, K-type or J-type thermocouple junctions could be formed using conductor -C"ls 0- chlromel/alumel or iron/constantan, respectively.

Moreover, ir should be appreciated that a printed circuiz: thermocouple and the methods by which ir is made and used as described above, for purposes such as Z-ave been described above pertaining to the training of personnel and evaluation of equipment, etc., represent only a prefferred intended application of the invention on the part of the inventors which, by no means, reflects the full utility of the invention. That is, an array of thermocouples on a printed circuit thermocounle arrangement, in accordance with the present invention, could be utilized for almost any situation wherein it would be desirable to obtain a temperature profile of thermal effects. For example, thermal insulation or heat loss effects could be 18 - evaluated in a manner similar to that achievable by way of infrared photography, by covering one or more surfaces of a subject of study-with a printed circuit t.-lermocouple arrangement having suitable pattern(s) of thermocouples produced in accordance with the present invention. Furthermore, by using a flexible circuit' board type substrate, such as one formed of poly-imide such a thermocouple arrangement could be easily applied to arcuate and other nonplanar surfaces.

S t i 11 further, t-1he method of fabricating thermocouples via printed circuit technology in accordance with the present invention even offers a new, "o-wer cost alternative to conventionally constructed thermocouples for use as a substitute for such standard thermocouples in any application for which small individual thermocouples have been heretofore used- could be in partJcular, a Single large support formed with a myriad bf individual thermocouple junctions in accordance with the present 4nvenrion, which support, with the thermocouples formed into a corresponding number thereon, then being cut up of individual thermocouple elements, each orr- which has resoective one o-f thermocouple junctions thereon, at frac--ion of the cost associated with the existing zechnicues for oroducing thermocouple elements. Here again, zhe use of thin flexible substrate materials may be advantageous- T present invention is susceptible jhus, since the off numerous other changes and modifications as will be annarenz to those of ordinary skill in the art, the present invention should not be considered to be.mited to the detail's of the various embodiments shown and described herein, but rather should be viewed as encompassing all such changes and modifications as are within the scope of the appended claims.

19 - I_.

t. claims:

1. Thermocouple arrangement for providing temperature data, resulting from use of at least one thermally affecting process on an electronic assembly via an emulated production/rework/repair operation, comprising an electrically insulative support, a layer of a first conductor material applied on a first surface of said support, at least one printed circuit pattern of a second conductor material, that is dissimilar to said first conductor material, formed on at least one other surface of the support; wherein said prised of circuitry printed circuit pattern is comi having thermocouple pad terminal portions, signal monitoring connection portions and trace interconnections running therebetween; wherein at least one thermocouple pad terminal portion of the printed circuit pattern of the second conductor is connected to the layer of the ffirst conductor material by an electrical connection that is formed of said first conductor material and which extends through said support therebetween in a manner creating a thermocouple junction on the respective thermocouple Dad terminal oort-ion- 2. Thermocouple arrangement according to clair. 1, where-i- said layer of first conductor materiall is a printed circuit pattern having signal monitoring and terminal portions, and trace interconnect _Jons running there';'.-etween.

3. 'IT'hermocouple arrangement according to claim 2, wherein said printed circuit patterns are formed on opposite outer side surfaces of said electrically insularive support.

11 4. Thermocouple arrangement according to claim 3, wherein said electrical connection is formed by firsconductor material being plated through a through hole in the support and onto terminal port'lons of said printed circuit patterns in a manner mechanically as well as electrically connecting the terminal portions of the patterns of the first and second conductor materials.

5. Th.ermocouple according to claim 4, wherein said printed circuit patterns have a plurality of terminal portions, and wherein e ecurically connected t all of the pattern traces therefor are of equal width.

6. Thermocouple arrangement according to claim 5, wherein some of said thermocouple pad terminal portions are situated at locations corresponding with a lead array of an electrical component to be mounted on the support, and wherein or-her of said thermocouple pad terminal oortions are disposed in an area surrounding said corresponding locations for providing temperature data at locations that are disposed away from areas at -ion/rework/repair operation is which --he oroduct Peformed- 7. Thermocouple arrangement according to claim 4, L wherein some of said thermocouple pad terminal portions are situated at locations corresponding with a lead array of an electrical component to be mounted on the support, and wherein other of said thermocouple pad zerminal Portions are disposed in an area surrounding said corresponding locations for providing temperature daza at locations that are disposed away from areas at which the production/rework/repair operation is pe-f, orme,-,.

8. Thermocouplearrangement according to claim 4.

w.here-in said printed cirduit patterns have a pluralityof electrically connected terminal portions, and wherein the pattern trace for some of taid terminal portions is of a different width relative to the pattern trace for other of said terminal portions for simulating differing thermal mass configurations.

9. ThermocouDle arrangement according to claim 4, id through hole is open.

wherein sa- 10. Thermocouple arrangement according to claim 4, wnerein said through hole is at least partially closed.

11. Thermocouple arrangement according to claim 4, wherein the amount of first conductor material provided in a said through hole is predetermined as a means for simulating heat sinks.

12. Thermocouple arrangement according to claim 1, where-in said printed circuit pattern of the second c o n duA ctor material has a plurality of electrically I- the connected terminal portions, and wherein all o. for are of equal width.

na--"ern traces thereL 13. Thermocouple arrangemenz according to -!aim 12, wherein some of said thermocouple pad -erm-i---al portions are situated at locations corresponding with a 'Lead array of an electrical component to be mounted on the support, and wherein oth.er of said thermocouple pad terminal portions are di, sposed in an area surrounding said corresponding locations for providing temperature data at locations that are disposed away from areas at which the production/rework/repair operation is peformed.

1 - - 14. Thermocouple arrangement according to claim 1, wherein said printed circuit pattern of the slecond conductor material has a plurality of electrically connected terminal portions. and whexein the circuitry C F said terminal portions is of a different for some o.area relative to the area of other of said terminal Dortions for simulating differing thermal mass configurations.

15. Thermocouple arrangement according to claim 1,.4here-in. said thermocouple junction is constructed for surface mounting of a lead of an electrical component thereon.

I 9. Thermocouple arrangement according to claim 1, wherein said thermocouple junction is constructed for through hole mounting of a lead of an electrical comoonent thereon.

1 L7. Thermocouple arrangement according to claim 1,.v,;here-i---1 said layer of first conductor material is of a foil covering said first surface of said e-lecur-icallv_ insulative support, at least in an area i-here--fj that- is coextensive with an area of said other surface of the support upon which said printed circuit:a-.- ce--n is formed.

B. l Thermocouple arradgement according to claim 1, id wInere-in saelectrically insulative support is formed of a plurality of circuit board layers, wherein said of first conductor material is formed on an -i.te--ace surface of the support located between a pair of sa--d board layers and wherein a said printed circuit pattern of the second conductor material is formed at each of opposite outer surfaces of said board.

23 - 19. Thermocouple arrangement according to claim 18. wherein the lay6r of said first conductor material covers said interface surface.

20. Thermocouple arrangement according to claim 18, wherein said layer of first conductor material is a printed circuit pattern having signal monitoring and terminal portions, and trace interconnections therebetween.

21. Thermocouple arrangement according to claim 18, wherein said electrically insulative support is comprised of at least three circuit board layers, f second and wherein at least one additional pattern o conductor material is disposed at a respective additional interface surface of the support in a manner forming -intermediate thermocouple junctions at locations at which the additional pattern intersects -he layer he electrical connections extending between z of firsz conductor material and the patterns of second conductor material formed on the outer surfaces of the suppo-rt.

22. -.-eriiocoup-',e arrangement according to claim 21, w,-.ere--,n the layer of said first conductor material covers said interface surface.

23. Thermocouple arrangement according to claim 21, wherein said layer of first conductor material is a printed circuit pattern having signal -L monitoring and terminal portions, and trace interconnections therebetween.

24 Thermocouple arrangement according to claim 18, wherein said thermocouple junction of at least one of said patterns is constructed for surface - 24 mounting of a lead of an electrical component thereon.

1 25. Thermocouple arra ngement according to claim 18, wherein said thermocou]le junction of at least one of said patterns is constructed for through hole mounting of a lead of an electrical component thereon.

26. Thermocouple arrangement according to claim 18, wherein said printed circuit patterns have a plurality ol- electrically connected terminal portions, and wherein the circuitry for some of said terminal portions is of a different area relative to the area of other of said terminal portions for simulating differing thermal mass configurations.

27. Thermocouple arrangement according to claim 18, wherein at least one said electrical connection is constructed as a means for simulating a heat sink.

28. Thermocouple arrangement according to claim 1, where-'n said conductor materials are selected from the group consist-ing of copper and constantan, chromel and a!Lb-tie-l, and iron and constantan.

29. Mezhod of making a thermocouple arrangement for providing temperature data resulting from use of a thermally affecting process on an electronic assembly via an emulated production/rework/repair operation, comprising the steps of:

(A) applying a layer of a first conductor material on a first surface of an electrically insulative support; (B) forming at least one printed circuit pattern of a 3, - -second conductor mate.rial, that is dissimilar to said ---firsr- conductor material,"on at least one other surface of the support, said pattern being comprised of circuitry having thermocouple pad t_erminel portions, signal monitoring connection portions and trace interconnections running therebetween; and (C) connecting at least one thermocouple pad terminal portion of the printed circuit pattern of the second conductor to the layer of the first conductor material by forming an electrical connection of said first conductor material which extends through the support -Prom said layer of first conductor material to the thermocouple pad terminal portion of the circuitry in a manner creating a thermocouple junction thereon.

30. Method 'according to claim 29, wherein step is performed by forming a printed circuit par-tern of the first conductor material on said first surface.

31. Method according to claim 30, wherein step (C) comorises the steps of forming a through hole in the electrically insulative support and the terminal :r the Jirst and second conductor materials, nortions ol f - and plating first conductor material through said through hole and onzo the terminal portions in a manner creating a mechanical as well as an electrical connection therebetween.

32. Method according to claim 31, comprising the 9 further step of inserting a plug into said through hole J:

for enabling surface mounting of a lead of an electrical component thereover.

33. Method according to claim 31, wherein said plating through said through hole is performed so as to leave a portion of said opening unobstructed for through hole mounting of a lead of an electricalcomponent therein.

34. Method according to claim 29, wherein step (C) comprises the steps of forming a through hole in the electrically insulative support and the terminal portions of the first and second conductor materials, and plating first conductor material through said through hole and onto the terminal portions in a manner c.reating a mechanical as well as an electrical connection therebetween.

35. Method according to claim 34, comprising the further step of inserting a plug into said through hole for enabling surface mounting of a lead of an electrical comoonent thereover.

36. method according to claim 34, wherein said plating through said through hole is performed so as to leave a portion of said opening unobstructed for through hole mounting of a lead of an electrical comDonent therein.

37- Method according to claim 29, wherein step (B) 'Ls performed in a manner creating a pattern trace Lo-- some of said terminal portions that is of a di, i :,r-erent width relative to other of said terminal r)ort-ion f o r simulating dif f ering thermal mass confIgurations.

38. Method according to claim 29, wherein said printed circuit pattern is formed by laminating a conductor foil approximately.002 inch thick to the support, producing a circuit pattern of said foil by phoromasking techniques and removing unwanted portions 6.

of the circuit pattern produced using an etchant.

39. Method of obtaining temperature data k - pertaining to the performance of a thermalIly affecting process on an electronic assembly by the emulating of a produc tion/rework/ repair operation, comprising the steps of:

(A) emulating an electronic assembly by providing a ller,mocouDle arrangement, comprising an electrically insulative support, a layer of a first conductor material applied on a first surface of said support, at least one Printed circuit pattern of a second conductor material, that is dissimilar to said first conductor material, formed on at least one other surface of the support; wherein said printed circuit pattern is compr,sed of circuitry having thermocouple pad terminal portions, signal monitoring connection portions and trace interconnections running therebetween; wherein at least one thermocouple pad terminal portion of the printed circuit pattern of the second conductor is connected to the layer of the first conductor material by an electrical connection that is formed of said first conductor material and which extends through said support therebetween in a manner creating a thermocouple junction on the respective thermocouple Dad terminal portion, so that leads of the electronic component are disposed on respective thermocouple pad terminal portions o-f said printed circuit pattern; (B) emulating a produc ti.on/rework/ repair operation during which a thermally affecting process is actually performed with respect to said thermocouple arrangement; :ng an electrical signal, representative of (C) produc 1 _temperature data pertaining to the effects of at least ---S a i d thermally affecting process of the production/ rework/ repair operation emulated, via at least one said thermocouple juhction; and (D) generating an output from said electrical signals by which said effects can be evaluated.

40. Method according to claim 39, wherein step B) steps includes the of disposing leads of at least cne electronic component on respective thermocouple pad erminal portions of said printed circuit Pattern, and forming an electrical connection between the leads of the electronic component and the respective thermocouple pad terminal portions by said thermally affecting process; wherein said process involves the application of heat and said electrical signals pertain to the effects thereof upon the insulative support and electronic component.

41. 1. Method according to claim 40, wherein said production/rework/repair operation comprises soldering process.

a 42. Method according to claim 41, wherein said scidering process is a through hole mounting process.

43. Method according to claim 41, wherein said soldering p.rocess is a surface mounting process.

44. Method according to claim 41, wherein said production/rework/repair process is performed by applying heat from at least a side of the thermocouple arrangement at which the electronic component is applied.

X 1 4 45. Method according to claim 40, wherein said soldering process is a suriace mounting process.

46. Method according to claim 45, wherein said production/rework/repair process is performed by applying heat from at least a side of the thermocouple arrangement at which the electronic component is applied.

47. Method according to claim 40, wherein said 1-emperature data representative electrical signals are produced in a manner reflecting the effect of a varying thermal mass configuration of an electronic assembly that -is being emulated.

48. Method according to claim 40, wherein temperature data is obtained from thermocouple junctions at a plurality of locations at at least one surface of the support.

49. Method according to claim 40, wherein zemperature data is obtained from thermocouple junctions at a plurality of locations at a plurality of 1 surfaces of the insulative support.

50. Me--hod according to claim 49, wherein said plurality of surfaces at which temperature data is obtained includes interface surfaces between circuit board layers of which said insulative support is formed.

51. Method according to claim 39, wherein leads of at least one electronic component are electrically connected to respective thermocouple pad terminal portions; wherein step (B) includes the application of heat to disconnect the leads of the electronic component from the respective thermocouple pad terminal portions, and wherein said electrical signals pertain to the effects of said.. heat Upon at least the insulative support.

52. Method according to claim 51, wherein said electrical signals also pertain to the effects of said application of heat upon other electrical components mounted upon said insulative support.

53. Method according to claim 51, wherein said rework/repair process is a desoldering process.

54. Method according to claim 53, wherein the electrical connections are of the surface mount type.

55. Method according to claim 53, wherein the electrical connections are of the through hole type.

56. Method according to claim 53, wherein said heat is applied from at least a side of the thermocouple arrangement at which the electronic component is applied.

57. Method according to claim 54, wherein said prcFduction/rework/ repair process is performed by applying heat from at least a side of the thermocouple arrangement at which the electronic component is connected.

58. method according to claim 51, wherein said temperature data representative electrical signals are produced in a manner reflecting the effect of a varying thermal mass configuration of an electronic assembly that is being emulated.

X -L 59. Method according to claim 51, whereit temperature data is obtained from thermocouple junctions. at a plurality of- locations at. at least one surface of the insulative support.

60. Method according to claim 51, wherein temperature data is obtained from thermocouple junctions at a plurality of locations at a plurality of surfaces of the insulative support.

61. Method according to claim 60, wherein said plurality of surfaces at which temperature data is obtained includes interface surfaces betweencircuit board layers of which said insulative support is formed.

62. Method according to claim 39, wherein said thermally affecting process is performed with an apparatus, and wherein the output generated in step (D) is utilized to evaluate thermal performance characteristics of said apparatus.

63. A printed circuit thermocouple comprising an electrically insulative support, a first conductor material applied on a first surface of said support, a printed circuit pattern of a second conductor material that is dissimilar to said first conductor material, formed on at least one other surface of the support, said printed circuit pattern being comprised of circuitry having at least one thermocouple pad terminal portion, signal monitoring connection portion, and trace interconnection running therebetween; wherein the at least one thermocouple pad terminal portion of the printed circuit pattern of the second conductor is connected to the layer of the first conductor material by an electrical connection that is formed of said first conductor material. and which extends through said support therebetween in a manner creating athermocouple junction on the respective thermocouple pad terminal portion. JI 64. Printed circuit thermocouple according to claim 63, wherein said layer of first conductor material comprises a printed circuit pattern having at least one signal monitoring and terminal portion with a trace interconnection running therebetween.

- 65. Printed circuit thermocouple according to claim 64, wherein said printed circuit pattern of the second conductor material has a plurality of said terminal portions at which a respective said thermocouple junction is formed.

66. Method of making a printed circuit thermocouple comprising the steps of:

(A) applying a layer of a first conductor material on a first surface of an electrically insulative support; (B) forming at least one printed circuit pattern of a second conductor material, that is dissimilar to said firsr-conductor material, on at least one other surface o'LE the support, said pattern being comprised of circuitry having at least one thermocouple pad terminal portion, signal monitoring connection portion, and trace interconnection running therebetween; and (C) connecting said at least one thermocouple pad terminal portion of the printed circuit pattern of the second conductor to the layer of the first conductor material by forming an electrical connection on said first conductor material which extends through the 4 IL - 33 support from said layer of first conductor material to the thermocouple pad terminal portion of the circuitry in a manner creating a thermocouple junction thereon.

67. Method according to claim 66, wherein step (A) is performed by forming a printed circuit pattern of the first conductor material on said first surface.

68. Method according to claim 67, wherein step (C) comprises the steps of forming a through hole in the elect rically insulative support and the terminal portions of the first and second conductor materials, and plating first conductor material through said through hole and onto the terminal portions in a manner creating a mechanical as well as an electrical connection therebetween.

69. Method according to claim 68, wherein said method is performed so as to create a multiplicity of said thermocouple junctions 70. Method according to claim 69, comprising the further step of subdividing said support in a manner creating a plurality of separate and distinct thermocouple elements, each of which has at least one said thermocouple junction formed thereon.

71. A thermocouple arrangement for providing temperature data, resulting from use of at least one thermally affecting process on an electronic assembly via an emulated production/rework/repair operation, substantially as hereinbefore described with reference to the accompanying drawings.

72. A method of making a thermocouple arrangement for providing temperature data resulting from use of a thermally affecting process on an electronic assembly via an emulated production/rework/repair operation, substantially as hereinbefore described.

73. A method of obtaining temperature data pertaining to the performance of a thermally affecting process on an electronic assembly by the emulating of a production/rework/repair operation, substantially as hereinbefore described.

- 33a 74. A printed circuit thermocouple substantially as hereinbefore described with reference to the accompanying drawings.

75. A method of making a printed circuit thermocouple substantially as hereinbefore described.

1 j Published 1990atThe Patent Office. State House. 66 71 High Holb-lrr..Lond, nWC1R4TP-F-urther copies rn@L,, be obtainedfrorn The Pat'en Office Sales Branch, St Mary Cray. Orpington. Kert BR5 3RL Printed by M12tiplex techrAques ltd. St Ma::; Crky. Kent. Con 1 87,