CA1200439A - Carbon-based soldering and de-soldering tip and method of manufacturing same - Google Patents

Abstract

Abstract:
A replaceable de-soldering tip for a de-soldering tool comprises a body of carbon-based material having an attachment portion for joining with the tool, an inter-mediate portion adjoining the attachment portion and a solder-wetting portion adjoining the intermediate portion.
A central elongated vacuum passage is formed along the length of the body for allowing the removal of melted solder, the wall of this passage being uncoated, bare carbon-based material.

Description

BACKGROUND OF THE INVENTION
This application is a division of application Serial No. 406,163 filed J~ne 28, 1952.
Field of the Invention The present invention relate~ to a carbon-based soldering or de-soldering tips for use with soldering irons and de-soldering tools, respectively. The tip includes plated solderin~ surfaces.
More particularly, the invention is directed to replaceable sol-dering and de-soldering tips which are less expensive than sthn-dard copper tips, have longer working lives, resist pittingl and eliminate or greatly reduce the problems associated with standard soldering tips. The invention fur~her relates to a method for manufacturing carbon-based soldering and de-soldering tips. The tips are resistent to both high temperatures and corrosion and can be used with all types of soldering irons and de-soldering tools, including temperature-controlled soldering irons and de-soldering tools~
Descri tion of the Prior Art It is well~known that all soldering irons have soldering tips, and the majority of soldering irons are adapted ~o receive replaceable soldering tips. Replaceable tips are normally inserted into a tip-receiving bore of a soldering iron and are threaded or fi~ed in place by a set screw or similar mechanical device~ It is further Xnown that many temperature-controlled ~oldering irons include a sensor element extending within the iron's tip-receiving bore. The sensor element fits within a por-tion of a permanent or replaceable soldering iron tip.
It is also well-known that de-soldering tools have replace-able de-soldering tips which are normally screw-threaded to the tool. These tips include a central tubular vacuum passage through which the melted solder is drawn.

``1~ ~,p Soldering and de soldering tips have conventionally been formed from a copper body due, in part, to the heat conductivity of such copper bodies. This ~tandard use o copper as a body of l~thes tips has, however, presented a number of problems. When-¦ever copper comes into contact with commonly used solders, the solder reacts with the copper and dissolves it. Therefore, cop-per tips must be plated at least in the solder-wetting portion of the tips. Furthermore, the tubular vacuum passage of a de-soldering tip must be plated or otherwise protected from con-) ¦ tact with the melted solder. If it is not, the passage becomesclogged. The plating of the copper base, however, does not com-pletely solve the problem since the coatings wear over time and most often initially have slight imperfections and cracks.
Heated solder seeps through such imperfections and worn areas and ; ¦ dissolves the copper base, resulting in cavities in the tip simi-lar to tooth cavities. Thus, copper based tips often lose their shape an~ ef~ectiv2ness after a short period of use.
The use of copper as the base of soldering and de soldering tips pr sents an additional and signiicant prohlem. Copper, when subjected to the high temperatures necessary for soldering or de-soldering, quickly oxidizes. This oxidation damages a tip's surface and, more importantly, often results in a freezing of a replaceable tip to the body of the soldering iron or de-soldering tool at the interface of the tip and the tip-receiving bore. Furthermore, if a soldexing iron has a tempera-ture sen~or inserted into a bore in the tip, the tip and the tem-perature sensor often freeze together. This free~ing of parts damages the soldering iron itself and often necessitates repair renders the iron comple~ely unuseable.

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The oxidation of a copper tip poses an additional heat transfer problem with soldering tips. To insure proper heat transfer between the heating element and the shank of the solder-ing tip, the shank must fit snugly in the opening of the heating element~ However, the shank o the soldering tip oxidizes at elevated temperatures. The resultant layer of oxide at the interface of the shank and the soldering iron acts as an insula-tor which decreases the transfer efficiency between the heating element and the soldering tip.
) With temperature-controlled soldering irons, the oxidation tends to decrease the sensitivity of control~ For the heat sen-sor to measure the tip temperature accurately, it must fit snugly within the sensor hole. Howe~er, the oxidation of the copper at the sensor-tip interface decreases the heat transfer and sensi-tivity of the control and often causes the tip to freeze to the sensor. Thi5 freezin~ problem is so significant that in most commercial applications the bore receiving the sensor is oversi-zed to eliminate or reduce the freezin~. This procedure, how-e~er, decreases heat trans~er and thus the sensitivity of the ) temperature control.
One technique used to overcome the freezing problem at the interface of the tip and soldering iron has been to form a stainless steel sleeve over the portion of the copper tip which is received by the soldering iron. While such a stainless steel sleeve has been effective in reducing the freezing problem at the tip-iron interface, th~ heat transfer properties of the tip are greatly reduced because there is no molecular bond between the stainless steel and the copper. Furthermore, this technique is expensive and does not correct the freezing problem presented at I .

~a~ Q 4~ 9 the sensor-tip inter~ace in temperature-colltrolled soldering irons.
With respect to the foregoing problem at the sensor-tip ,linterface, it has been found that it is difficult, if not impos sible, to electroplate the inside of the sensor hole without very !expensive individual handling of the tips. Applicant is not ¦I,aware of any presently available means to economically overcome ¦¦this freezing problem.
~ With respect to de-soldering tips, the tubular vacuum pas-3 1l sages now on the marXet often include a stainless steel linirlg ¦which will not react with the melted solder and can be easily cleaned. Such linings significantly add to the expense of such de-soldering tips.
Because of the miniaturization presently occurring in the electronics field, soldering and de-soldering tips in many appli-cations have decreased substar,tially in size to permit precise sol~ering. The demand for smaller soldering tips aggravates the problems presented by the pitting and oxidation of copper-based ~ips.
O Finally, the increasing cost of copper has made copper sol-dering and de-soldering tips iess commercially desirable. The short service life of copper tips increases this expense.
Summar~ of the Invention It is therefore an object of the pre~ent invention to pro-vide a soldering or de-soldering tip which overcomes the pitting and oxidation problems presented by commercial tips now on the ¦market. It is further an object of the present invention to pro-¦vide a method of manufacturing such tips.

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To this end, the invention consists of a replaceable de~solder.ing tip for a de-soldering tool comprising: a body of carbvn-based material having an attachment portion for joining with said tool, an intermediate portion adjoin-ing said attachment portion, a solder wetting portion adjoining said intermediate portion, and a central elongated vacuum passage formed along the length of said body for allowing the removal of melted solder, the wall of said passage being uncoated, bare carbon-based material.
The invention also provides a method of manufacturing de-soldering tips for a de-soldering tool haviny a tip-receiving bore and a vacuum source for removing melted solder comprising: forming a de-soldering tip body of carbon-based material having an attachment portion for insertion into said tip-receiving bore, an intermediate portion adjoining said attachment portion, a solder-wetting portion adjoining said intermediate portion~ and a central elongated vacuum passage formed along the length of said tip for allowing removal of melted solder, electro-plating at least the intermediate portion and the solder-wetting portion with a coating of iron, electroplating at least the intermediate portion with a coa~ing of nickel ~3~9~3~

over said iron coating, electroplating at least the intermediate portion with a coating of chrome over said nickel coatinq, and stripping all coatings on the ~all of the elongated vacuum passage to expose uncoated, bare carbon-based material surface.
It is to 'oe understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an example of a preferred embodiment of the invention and together with the description serve to explain the principles of the invention.

-Fig. 1 is a side view illustrating one em~odiment of~he invention.

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Fig. 2 is an enlarged cross-sectional view taken along lines

2-2 of Fig. l.
Fiy. 3 is an enlarged cross sectional view taken along the ',lines 3~3 of Fig. l, s Fig. 4 is a side view illustrating a second preferred embod-'iment of the invention.
'i Fig. 5 is an enlarged cross-sectional view taken along the lines 5-5 of Fig. 4.
¦ Fig. 6 is an enlarged cross-sectional view t~ken along the I lines 6~6 of Fig. 4.
Fig. 7 is an enlarged cross-sectional view taken along the lines 7-7 of Fig. 4.

i Fig. 8 is a side view showing an embodiment of the invention l fixed in a temperature-controlled electric soldering iron.
Fig. 9 is a ~ide view of a third embodiment of the invention.
Fig. lO is a fron~ view of the third embodiment of the invention.
Fig. ll is a cross-section of the third embodiment of the invention.
Detaile ~ of the Invention Reference will now be made in detail to the present pre-ferred embodiments of the invention, examples of which are illus-trated in the accompanying drawingsO
,5 Fig. l is a side illustration o one embodiment of a solder-ing tip made according to the present invention. The soldering ¦iron tip shown in Fig. l and designa~ed generally as numeral lO
includes a shank or attachment portion A, an intermediate portion B adjoining the attachment portion A, and a solder-wetting

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I portion C adjoining the intermediate portion B. In use, the shank or at~ac~ment portion A is inserted into a bore in the heating elemen~ of a soldering iron, as shown generally in Fig.
ii 8. The soldering tip 10 may include a ferrite iron heat sensing 11 element or magnesta~ 12 fixed to the distal end of the attachment portion Ao When the soldering tip 10 is inserted in a soldering ¦l iron the magnestat contacts with a temperature sensing device in the soldering iron. The attachment portion A is preferentially ¦I cylindrical in shape, and the tip 10 tapers generally along the j intermediate portion B and the solder-wetting portion C. The working end 14 of the tip 10 can be formed in a shape most bene-ficial to the particular application for which the tip is designed. If desired, the tip can include a shoulder 16 with bevel edges 18. Thi~ shoulder acts as a stop to properly posi-tion the tip 10 within a soldering iron and also serves as a bar-rier to stop any possible upward flow of solder from the solder-wettin~ portion C toward the attachment portion A.
As shown by the cross-sectional view of Fig. 2, the solder tip has an integral carbon body 20. Preferably, the carbon body can be made from pure carbon, carbon graphite, pyrolytic carbon or silicon carbide. The applicant has found that each of these above carbons provides an acceptable soldering or de-soldering tip base with suficient heat conductivity. It is believed that other carbon-based materials may b~ likewise acceptable.
The thermal conductivity of the carbon materials, as well as the costs, varies from material to material. Presently, appli-cant considers carbon graphite to he the preferred body material for most commercial applications. Carbon graphite has sufficient ~heat conductivity and is low in cost. Carbon graphite has a thermal conductiYity which approximates 6Q% of ~he normal thermal conductivity of pure copper and costs ]/3 to 1/5 as much. In special applications, other carbon-based materials may be more appropriate. For exarnple, if increased heat conductivity is desired, pyrolytic carbon can be fashioned to provide a much better thermal conductivity than copper. The cost of pyrolytic carbon, however, is 3-5 times as much as copper.
The carbon base provides several advantages over copper and other known base materials for solderinq and de-soldering tips. Carbon does not dissolve when placed in contact with solders. Furthermore, the carbon does not oxidize or react with other elements at high temperatures and does not have a liquid state. Furthermore, carbon materials are easily fabricated on standard machine tools, often at lesser costs than copper. Finally, as will be explained below, the carbon base readily accepts platings of metals during a plating process.
In the embodiment shown in Fig. 1, Fig. 2 and Fig 3, the soldering tip includes a coating of iron 22 formed over the entire exterior body of the tip. A coating of nickel plating 24 i~ formed over the iron coating 22 along the intermediate portion B and the attachment portion A, but not along the solder-wetting portion C. .Finally, a coating 26 of chromium is formed over the nickel plating 24 along the intermediate portion B and the attachment portion A, but not along the solder-wetting portion C.
The iron coating 22 provides a wettable surface in the working area 14 of the tip. The nickel-chrome coating localizes the wettable working surface so that precision soldering can be achieved. The nlckel~chrome coating also impedes the upward flow of solder along the intermediate portion B and toward the ~2~

attachment portion A. Without the coating, solder would flow to the point where the soldering tip and soldering iron meet and might bond the tip and iron together.
In the embodiment shown in Fig. 1, the attachment portion includes the exterior coatings of iron, nickel and chrome. The resultant carbon-based tip is not subject to the degree of oxidation that a copper based tip is, since the carbon-based material will not oxidize. As will be described below, it is possible to further reduce the oxidation problems by stripping all coatings from the attachment portion A so that only uncoated, bare carbon interfaces with the soldering iron.
A second embodiment of a soldering tip made according to the invention is shown in ~ig. 4, Fig. 5, Fig. 6, and Fig. 7, wherein like numbers are used to refer to like parts. The soldering tip 10 shown in Fig. 4 includes an elongated bore 19 formed in the attachment portion A and si~ed to receive snugly a temperature-sensing element of a soldering iron. The soldering tip in Fig. 4 is similar to the tip in Fig. 1 and includes a carbon body 20, an iron coating 22, a nickel coating 24, and a chrome coating 26. In addition, the tip includes a thin coating of dull nickel ~1 formed between the carbon body 20 and the iron coating 22 along the intermediate portion B
and the solder-wetting portion C. As will be described below, the thin coating of dull nlckel is necessary only when the tips are coated by a barrel plating process, rather than a rack plating process. The primary distinction between the embodiment shown in Fig. 1 and Fig. 4 is that the attachment portion A
does not include any metal coatings in the finished product.
Furthermore, there is no coating on the inner surface of the elongated bore 19. This embodiment is the present pre~erred embodiment of a solderin~ tip made in accordance ~ith the invention and prevents any, possible oxidation or freezing of the attachment portion A to the soldering iron or to the temperature-sensing element of the soldering iron.
In the preferred embodiment, the coating of iron has a thickness in the range o~ 6 to 10 mils, the outer coating of nickel has a thickness in the range of 0.05 to 1 mils, and the coating of chrome has a thickness in the range of 0.5 to 1 mils.
If an inner coating o~ dull nickel i5 used, that coating is approximately 0.5 mils thicko Fig. 8 illustra~es an em~odiment of the present invention attached to a temperature-controlled soldering iron with a temperature-sensing element. The soldering iron includes a general body portion 30 with a tip-receiving bore 32. Within the tip-receiving bore 32 is a sensor element 34 for ~ensing the temperature o~ the soldering tip. When the soldering tip 10 is inserted into the bore 32 of soldering iron 30, the sensor 34 is snugly received by the elongated bore 19. A tip nut 36 or a similar mechanical device is used to fix or lock the tip to the soldering ironO
Figs. 9 through 11 illustrate an embodiment of a de-soldering tip 40 made according to the invention. The de-soldering tip 40 includes an attachment portion A, an inter-mediate portion`B adjoining the attachment portion A, and a 2S solder-wetting portion C adjoining the intermediate portion B.
The tip 40 includes a central tubular vacuum passage 42, and the attachment portion A includes mounting threads 44. In use, the de-soldering tip 40 is threaded onto a de-soldering tool, which is well-known in the art. In operation, the tip is heated and then brought into contact with solder which the ¢~4z3a3 operator desires to remove from a circuit. A vacuum source is connected to the vacuum passage 42 so that as the solder is melted, the melted solder is drawn off through the t~be 42.
The de-soldering tip 40 shown in Fig. 11 has an integral carbon body 46 and includes a coating of iron 48 formed over the entire exterior body of the tip. A coating of nickel plating 50 is formed over the iron coating 48 along the intermediate portion B and the attachment portion A, but not along the solder-wetting portion C. Finally, a coating 52 of chromium is formed over the nickel plating 50 along the intermediate portion B and the attachment portion A, but not along the solder-wetting portion C. The coatings are the same coatings used on the soldering tips previously described and serve the same purposes. If it is desired to coat the de-soldering tip 46 by a barrel coating process, an additional dull nickel coating would first be plated directly on the carbon base by a rack plating process, and the additional coatings would be made by a barrel coating process.
In the de-soldering tip 40, the wall of the tubular vacuum passage 42 is uncoated, bare carbon. The melted solder will not adhere to this carbon, and therefore it is unnecessary to plate the passage or place a stainless steel tube in the passage.
The soldering and de-soldering tip of the present invention provides several benefits not found in commercial copper solder-ing and de soldering tips. First, the carbon body is not prone to oxidation or dissolving. Because of these characteristics, the carbon body will not cavitate or oxidize at points of dis-continuity or wear in the metal coatings. The tip of the present invention, therefore, eliminates the problems of pitting, heat transfer ]oss by oxidation, and freezing by oxidation~ 1~e present invention also provides a longer lasting tip at a lower cost. ~s will be described ~elow, ~he carbon tip can be coated l more quickly than copper, and the porous material o~ the carbon ¦ tip absorbs impuri~ies in the plating baths and results in a more defect-free plating job.
The presently preferred method of making the soldering and de-soldering tips will now be described. First, a tip is ~ machined to the desired shape by a typical m~chining element such I as a lathe or turning machine. It has been found that the pre-ferred carbon materials are easily adaptable to such machining~
Due to the production of dust during machining, special dust col-lecting equipment should be used~
In the preferred process, after the carbon base is formed, the desired coatings are electroplated on the base by a rack or barrel coating process, or a desired combination of bothO Both of these coating processes are well-kno~n in ~he art. The pre-ferred process depends upon the availability of coating machinery, the number o tips to be produced, and the economics of operation.
If the tips are to be coated by a rack coa-ting process, the tips are first electroplated with a coating of iron through the use of a common iron plating bath, such as iron Fluoroborate.
l Next, a coating of nickel is electroplated over the iron coating, ¦ and finally a coating of chrome i5 electrop1ated over the nickel coating. Plating baths for electroplating nickel and chrome are well-known.
Ater the chrome electroplating~ the nickel and chrome oatings ~re stripped from the solder-wetting portion of the tip ~13-~1 1 to expose the iron coating as the wetting surface. If desired, the nickel and chrome coatings can also be stripped from the attachment portion of the tips.
~ It is believed that t~e barrel coating process may be more economical than a rack coating process, particularly if the tips are produced on a large scale. If tips are to be made by the 'I barrel coating process, it is preferable first to place a thin dull coating of nickel over the base by a rack coating process.
Il This thin coating strengthens the pointed end of the tip 50 it l¦ will not break during ~he barrel coating process. The remaining i steps of electroplating iron, nickel and chrome can be made in a barrel coating process. Then, at least the solder-wetting por-tion is stripped o any nicXel or chrome coatings to expose the iron coating as a wetting surface.
To achieve the present preferred embodiment of the soldering tip shown in Fig. 4, at least two differen~ procedures are pos-sibleO First, it is possible to coat the entir~ length of the tip and then strip any iron, nickel, and chrome coatings from the attachment portion of the soldering tip. In the alternative, the attachment portion can be masked during the electroplating pro-cess so that no coating is initially formed on the attachment portion of the carbon body.
Other embodLments of the invention will be apparent to those skilled in the art in consideration o~ the speci~ication and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, and with a true scope and spirit of the invention being indicated by the following claims.

Claims (3)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A replaceable de-soldering tip for a de-soldering tool comprising:
a body of carbon-based material having an attachment portion for joining with said tool, an intermediate portion adjoining said attachment portion, a solder-wetting portion adjoining said intermediate portion, and a central elongated vacuum passage formed along the length of said body for allowing the removal of melted solder, the wall of said passage being uncoated, bare carbon-based material.

2. The replaceable de-soldering tip of claim 1 further comprising:
first means coated on at least said solder-wetting portion for providing a wettable working surface, and second means coated over at least said intermediate portion, but not said solder-wetting portion, for localizing the wettable working surface and impeding the upward flow of solder along said intermediate portion and toward said attachment portion.

3. A method of manufacturing de-soldering tips for a de-soldering tool having a tip-receiving bore and a vacuum source for removing melted solder comprising:
forming a de-soldering tip body of carbon-based material having an attachment portion for insertion into said tip-receiving bore, an intermediate portion adjoining said attachment portion, a solder-wetting portion adjoining said intermediate portion, and a central elongated vacuum passage formed along the length of said tip for allowing removal of melted solder, electroplating at least the intermediate portion and the solder-wetting portion with a coating of iron, electroplating at least the intermediate portion with a coating of nickel over said iron coating, electroplating at least the intermediate portion with a coating of chrome over said nickel coating, and stripping all coatings on the wall of the elongated vacuum passage to expose uncoated, bare carbon-based material surface.