KR20040085194A - Electroplating solution containing organic acid complexing agent - Google Patents

Abstract

A solution used in connection with depositing one or more metals on an electroplatable substrate is disclosed. The solution is water; Metal ions; And complexing agents. A complexing agent is a complexing agent which is an organic compound having between 4 and 18 carbon atoms, which compound is a compound comprising a 5 or 6 membered ring containing at least one oxygen atom and at least two hydroxy groups. The compound is present in an amount sufficient to complex the metal in the solution and prevent oxidation of the metal. If necessary, suitable pH adjusting agents are included in the solution to maintain the pH of the solution in the solution in the range of 2 to 10 and preferably in the range of about 3.5 to 5.5. In the preferred pH range, the solution is particularly useful for electroplating composite articles having an electroplating portion and a non-electroplating portion without adversely affecting the non-electroplating portion.

Description

Electroplating solution containing organic acid complexing agent {Electroplating solution containing organic acid complexing agent}

The size of electronic components has decreased dramatically in recent years. The reduced size of the parts made it extremely difficult for these parts to be electroplated. In addition, many surface mount technology (SMT) devices have sensitive ceramic portions that can be damaged by strong acid or strong base solutions. To avoid this problem, it is preferable to use a neutral or near neutral pH electroplating solution.

US Pat. Nos. 4,163,700, 4,329,207, 4,640,746, 4, 673,470, and 4,681,670 disclose neutral or near neutral pH tin and tin / lead alloy electrolytes, particularly for sensitive ceramic SMTs. Formulated to be appropriate. Formulations disclosed in these patents describe the complexation of components such as citrate, gluconate, or pyrophosphate to complex tin and / or lead and make them soluble in solutions requiring elevated pH. Includes the first.

In the case of using the solutions shown in the prior art, there has been a constant problem of coupling or aggregation between devices during the electrodeposition process. It is generally known that in the case of tin or tin alloying small devices with flat surfaces, the devices are likely to cluster with each other during the plating process. In the case of barrel-plated SMT devices, up to 10% of the load can be coupled (ie sticking together). In some cases, the entire rod is fused together in large chunks. This problem depends not only on the plating solution composition but also on the plating method and the geometry of the device. This is a particular problem with tin-lead alloy electroplating.

In particular neutral or near neutral pH tin and tin / lead alloy electrolytes formulated to be suitable for sensitive ceramic SMTs have some level of utility but do not solve the problem of component fusion. It has also been found that the tendency to attack ceramics is strongly influenced not only by pH but also by electrolyte composition. Conventional electrolytes are known to attack low temperature calcined ceramics, a novel ceramic even at neutral near pH. There is also a problem with tin whiskers growing on thin plated parts. Thus, whisker resistant tin deposition is preferred. The present invention now overcomes these problems and provides solutions and processes that provide the desired deposits.

Summary of the Invention

The present invention relates to a solution used in connection with depositing one or more metals on an electroplatable substrate. The solution is water; An amount of metal ions sufficient to provide a metal deposit on the plateable substrate; And complexing agents. The complexing agent is an organic compound having between 4 and 18 carbon atoms, preferably including a 5 or 6 membered ring containing at least one oxygen atom and at least two hydroxy groups. Complexing agents complex the metal in solution and allow the metal to dissolve. Complexing agents also prevent the oxidation of metal ions in solution. Complexing agents prevent the metal from oxidizing from a lower valence state to a higher valence state when the metal ions have the ability to exist in solution in at least two different valence states. If necessary, an appropriate pH adjuster may be included in the solution to maintain the pH of the solution in the range between 2 and 10. In the most preferred pH range, the solution is particularly useful for electroplating composite articles having electroplating portions and non-electroplating portions without adversely affecting the non-plating portions.

Preferably, the complexing agent has one of the following structures:

Wherein each R is the same or different and is also hydrogen or a lower alkyl group having 1 to 3 carbon atoms, T is R, OR, or O = P (OR) _2- , Z is O = or RO-, n Silver 2-4, Z may be the same or different at each occurrence in the compound, and m is 1-3, or the complexing agent is a soluble salt having the above structure. Most preferred compounds include ascorbic acid, isoascorbic acid (also called erythorbic acid), dihydroascorbic acid, glucocorbic acid, galacturonic acid, glucoronic acid, and glucose-6-phosphate, or salts thereof do. Typical salts include alkali or alkaline earth metals. These complexing agents are generally present in amounts of about 25 to 200 g / 1. .

The present invention also relates to a method of electroplating a metal deposit on a composite article comprising electroplatable and non-electroplated portions. The method comprises contacting a plurality of such articles with any one of the solutions according to the invention and providing the metal electrodeposits on the electroplatable portions of the article without adversely affecting the non-electroplated portions of the article. Passing a current through the. Preferred metal electrodeposits are tin metals or tin-lead alloys and preferred articles are electronic components.

FIELD OF THE INVENTION The present invention relates to the deposition of metals and, more particularly, tin or tin on an article or article consisting of an electroplating substrate, such as a metal, or a composite article having an electroplating portion and a non-electroplating portion. It relates to the deposition of lead alloys. The present invention also describes a method for preventing fusion of multiple composite articles during an electrodeposition process. This method relates to the plating of small devices which have a large surface area per unit mass and are easy to fusing. Of particular interest here are devices such as surface mount capacitors and resistors having metal parts as well as ceramic, glass, or plastic parts.

Another advantage of the invention is described in the drawings:

1 is a micrograph of a substrate plated with tin in accordance with a conventional plating solution;

2 is a micrograph of the same substrate plated with tin according to the plating solution according to the present invention;

3 is an enlarged micrograph of a surface portion of a substrate plated with tin in accordance with a conventional plating solution; And

4 is an enlarged micrograph of the surface portion of a substrate plated with tin in accordance with the plating solution of the present invention.

It has now been found that fusion of electronic components, which are composite articles, can be largely eliminated by providing an electrolyte comprising one or more complexing agents disclosed herein. In particular, ascorbic acid and related compounds are most preferred for use as such complexing agents.

Complexing agents are preferably used in solutions for electroplating tin or tin-lead deposits, although the complexing agents may be used in solutions for electroplating other metals, especially metals having multiple valence states. These complexing agents assist in maintaining the metals in solution in either of their low valence states, thus facilitating the electroplating step and avoiding oxidation of the metals that affect the solution's proper functioning for its use. Make it possible. Stannic tin can also be complexed in this system.

Any complexing agent may be used in the present invention as long as it is a complexing agent of the formula given above. Preferred complexing agents are organic acids, preferably containing ascorbic acid, iso ascorbic acid, dihydroascorbic acid, glucocorbic acid, galacturonic acid, and glucononic acid (glucoronic acid). Salts of these acids can also be used, with preferred salts being alkali or alkaline metal salts. Ketogluconates, which can be converted into ascorbic acid in a bath, can also be used. Also suitable are heptagluconates which can be converted to similar acidic species in solution. Any of these complexing agents can generally be used in amounts of about 25 to 200 g / 1. Most preferred complexing agents are ascorbic acid or ascorbate, because these compounds are also relatively inexpensive and readily available.

Ascorbic acid may be included in the solution as an ascorbate such as ascorbic acid, potassium ascorbate or sodium ascorbate in simple form and / or in the form of an ascorbic acid-metal complex, for example as ascorbic acid tin. The latter case is preferably used when it is desired to make other acidic components, such as organic acids or organic acid salts, useful to maintain the desired solution pH. The amount of ascorbic acid should be at least sufficient to make the metal present at the given pH of the solution soluble in the solution. The amount of ascorbic acid so required is proportional to the metal concentration. When the tin concentration is 15 g / l, the preferred ascorbic acid concentration is about 45 to 200 g / 1.

Any electroplatable substrate can be plated using the solution of the present invention. Generally, these substrates are made of metals such as copper, nickel, steel or stainless steel. Many of today's commercial products that require electroplating are made smaller and smaller. In particular, electronic components are typical examples of such components.

In addition, these parts are composite articles having electroplating parts and non-plating parts. Whereas the metal part is metal or metallic, the non-electroplated part is generally ceramic, glass or plastic. The solution of the present invention is particularly useful in the case of electroplating such composite articles.

The electroplating solution may have a pH between 2 and 10, preferably in the range of about 3 to 7.5, and more preferably about 4 to 5.5, so that the solution can be adapted to the electronic component to be plated. do. In the case where the part has a metallic portion and an inorganic portion, the pH range, if desired, allows the deposition of metal on the metallic portion without adversely affecting the inorganic portion. In general, very high or very low pH solutions can damage the ceramic portions of the composite to be plated.

Basically any acid or base may be used for pH control, but these solutions preferably do not contain measurable amounts of free acid or free base. In general, because the solution is acidic, the base or basic component is used to convert the free acid to the corresponding salt. Preferred bases used for this purpose include sodium or potassium hydroxide as well as many other bases.

The solution is formulated to suit the substrate to be plated, preferably without adversely affecting the substrate. When a composite article having an electroplating portion and a non-electroplating portion is plated, the solution is formulated so as not to attack or crack the non-electroplating portion of the substrate. Simple tests can be done to determine substrate / solution suitability. The article to be plated is only quenched in solution for a time equal to or longer than the time required for the plating process. The temperature of the solution can be close to the temperature of the solution during the plating process, or an elevated temperature can be used for accelerated testing. The part may be immersed in the solution for the desired time, and then recovered and weighed to determine the weight loss caused by the solution attacking the article during quenching.

For example, composites used to manufacture capacitors are now made of low temperature calcined ceramics. These ceramics have a larger glass ratio than conventional ceramics and are more susceptible to attack during the plating process. Simple comparison tests were performed to determine suitability with various commercially available solutions and solutions according to the present invention. The capacitor was placed in a beaker containing the same amount of these solutions, and the weight loss of the parts was measured after 5 hours of quenching.

The results are shown in the following table:

solution % Weight loss after quenching in solution for 5 hours Comparative Example (Gluconate Electrolyzer with pH 3.5) 1.0% Comparative Example (Gluconate Electrolyzer with pH 4) 0.5% Comparative Example (Citrate Electrolyzer with pH 4.2) 5.0% Solution of the invention (ascorbic acid electrolyser with pH 5) 0.0%

The table shows that the present invention does not fundamentally have any effect on the capacitor, and there are substantial improvements in the plating process of such devices compared to traditional electrolyzers.

Particularly useful devices for plating such devices are U.S. Pat. It is disclosed in patent 6,193,858 and therefore need not be disclosed herein. As such, to the extent necessary, the entire contents of this patent are expressly disclosed herein.

An improved method for a system already patented in published international patent application WO 02/053809 is disclosed, and by this citation the entire contents of this international patent are expressly incorporated herein. The fact that the plating chamber can be immersed in an electrolyte, as disclosed in the present application, shows a significant improvement with regard to the use of external soluble electrodes.

The electrolyte comprising the complexing agent of the present invention not only minimizes fusion or coupling of the electroplated part, but also prevents tin or tin-lead alloy electrodeposition without adversely affecting the non-electroplated portion of the article. I found it possible. In this respect, these electrolytes are better than conventional electrolytes, and especially better for citrate based electrolysers. Complexing agents help maintain tin and / or lead in solution at the pH of the electrolyte. Certain complexing agents, in particular ascorbic acid, also assist as stabilizers that inhibit the oxidation of tin (II) (stannous tin) to stannic tin.

L-ascorbic acid (AA) is easily converted to L-dihydroascorbic acid (DAA). In addition, DAA is easily converted to the hydroxyl group of the adjacent carbon by two caton groups, and is easily returned to AA as the single bond connected to these atoms is converted to a double bond. AA is a strong reducing agent because it is easy to convert to DAA. In the plating solution of the present invention, AA assists in complexing tin ions in both divalent and tetravalent states of tin ions. This fact inhibits or at least minimizes the formation of tin oxide, which can precipitate to form sludge that adversely affects the action of the solution.

Preferred solutions of the present invention include water, divalent tin salts, and ascorbic acid as complexing agents, optionally divalent lead salts, salts for increasing electrical conductivity, surfactants, or anode dissolution. And a facilitating agent.

Tin (II) salts that can be used in the present invention include tin (II) sulfate, tin (II) chloride, tin (II) oxide, methanesulfonic acid tin (II), ascorbic acid tin (II) or any other suitable tin (II) salt. It includes the source of). The tin (II) concentration in the solution may be between 5 and 100 g / 1, most preferably between 10 and 50 g / 1. As pointed out in the foregoing, the complexing agents of the present invention also complex the tin (IV) salts, making it possible to add tin (IV) salts to the solution together with or instead of tin (II) salts.

Lead salts that may optionally be included to provide tin-lead deposits include divalent lead salts that are soluble in any solution, including, for example, lead methanesulfonate, lead acetate or lead ascorbate.

If necessary, the conductivity of the solution can be increased by adding salts. If pure tin solution is desired, simple salts such as potassium sulfate can be used. If it is desired to use tin-lead alloys, it would be appropriate to use potassium methanesulfonate or potassium acetate. Metal sulfide salts may also be used if their use is preferred. Any of these salts can be used to promote anode dissolution or assist in electrodeposition.

In order to improve the deposition crystalline structure or improve the deposition quality at high current densities, surfactants typically used in tin or tin alloy electrolytes can be added to the solution. Preferred surfactants include solution soluble alkylene oxide condensation compounds, solution soluble quaternary ammonium-fatty acid compounds, solution soluble amine oxide compounds, solution soluble tertiary amine compounds or mixtures thereof. One preferred surfactant is an alkylene oxide condensation compound and is present in an amount of about 0.01 to 20 g / l. Although some additives may perform better than others with respect to the coupling of the article to be plated, other traditional surfactants may be used because of the noncriticality of the deposit appearance in the device. have. One of ordinary skill in the art can conduct regular tests to determine the most appropriate surfactant, in particular for the plating solution.

If bright deposits are desired, aromatic aldehydes may be added in an amount sufficient to act as a brightening agent. If other traditional varnishes are desired, they may be used instead.

The substrate to be electroplated is preferably a composite article having a conductive portion and a non-conductive portion. The metal part is metal or metallic, while the non-conductive part is typically ceramic, glass or plastic. The solution of the invention is particularly useful for electroplating composite articles without adversely affecting the non-metallic parts of the article and without causing fusion of such parts.

The pH of the electrolyte is preferably maintained in the range of about 4 to 5.5 when it is desired to be plated on the composite substrate electronic component. The pH can be raised by adding caustic agents such as potassium hydroxide, ammonium hydroxide, sodium hydroxide or the like, or the acid can be lowered using an acid such as sulfuric acid or methanesulfonic acid. Alkanes or alkanol sulfonic acids, such as methanesulfonic acid, are preferred for use with tin-lead alloy solutions because sulfuric acid generates lead sulfate, which is insoluble in the solution and tends to precipitate. As pointed out above, a pH of about 4 to 5.5 results in the strongest prevention of aggregation of such metals. In addition, the amount of ascorbic acid should not be excessively greater than the amount necessary to complex tin to prevent or minimize aggregation.

Typical antioxidants used in tin and tin-lead solutions may be included in the solutions of the invention (eg, catechol or hydroquinoline as disclosed in US Pat. No. 4,871,429), but ascorbic acid is neutral or near neutral pH plating. It has been shown to be effective in inhibiting the oxidation of tin (II) (stannous tin) to stannic tin in solution. Thus, ascorbic acid has a dual function of acting as complexing agent and antioxidant in the solution of the present invention.

It has also been found that the plating of the non-conductive portion of the composite article and the fusion of the composite article can be formulated to minimize or greatly eliminate the solution of the present invention in order to have low homogeneous rolling power. These solutions are specially formulated to not deposit metal at low current densities. This is in contrast to traditional practice, where electrolytes are formulated to deposit metals in the widest current density range possible. In fact, most traditional tin electroplating solutions add a variety of additives to make the current density range of the electrodeposition process wider. It has now been found that fusion of components can be minimized by limiting the current density range of the electrodeposition process to a higher current density. Fusion is believed to occur due to the metal deposition process in intimate contact or in an electrolyte film between two parts between the part and the current supply. Since the deposition takes place in a thin film between two conductive surfaces, it must necessarily proceed at low current densities. If the electrolyte is formulated so that the plating process does not perform at low current densities, fusion is minimized.

It has been found that component fusion is closely dependent on the plating electrolytic cell composition and that the selection of the appropriate crystal refining agent or surfactant is critical to minimizing the fusion. For this reason, it has been found that simple electrolytes containing only metal salts and complexing agents electroplate surface mount technology (SMT) devices without fusion. The resulting tin deposit is a dark gray matte which is not suitable for commercial use. If a typical surfactant or crystal refiner is added to the electrolyte to improve deposition quality, very strong fusion will be observed in almost all situations. Cathode surface polarization, a result from surfactants and crystallizers, has been shown to strongly influence component fusion. In addition, electrolytes containing additives that impart limited coverage at low current densities tend to be less fused than those that include additives that impart high coverage at low current densities.

It is well known that solutions formulated to plate discrete components in barrels or other suitable equipment have a high uniform electrodeposition, allowing current to penetrate the rod and deposit metal in the bulk of the rod. . At low current densities, the plating rates are quite negligible so that the metals deposited under these conditions are not significant, but rather most of the metals are deposited at high current densities near the plating barrel boundaries. Thus, solutions that have high uniform electrodeposition properties for plating discrete parts in barrels or other suitable devices, unless the parts themselves have low current density areas such as hollow or blind holes. It has been found that providing is not required.

In addition, plating solutions that do not deposit metal at low current densities minimize the deposition of metal on the non-conductive portion of the composite. The phenomenon of extending the metal deposit from the conductive end of the article to the nonconductive portion is commonly referred to as creep or bridging. The extent of this phenomenon depends primarily on the composition of the nonconductive material. For example, ceramic materials that are partly conductive are more prone to metal creep than ceramic materials that are fully insulators. Creep is believed to occur due to leakage of current from the conductive portion of the article to the "non-conductive" portion during the electrodeposition process. By limiting the metal deposition process to high current density conditions, deposition of the metal into non-conductive portions can be minimized or eliminated.

The plating solution of the present invention can also assist in reducing or eliminating whiskers present in the deposits. This may be caused by the growth of filaments in the deposit under certain thermal conditions after plating. Such whiskers have been found to cause short circuit problems in low voltage equipment. In addition, whiskers may be separated from deposits and accumulate in other areas to further cause short circuit problems or to disrupt mechanical operation. Using the electroplating solutions disclosed herein, the degree of whiskering can be significantly reduced and eliminated completely.

Plating solutions according to the invention can be formulated or preferably formulated to have the following properties and advantages:

1. The plating solution according to the present invention can deposit white matte on semi-gloss deposition.

2. The plating solution according to the present invention will not damage the device to be applied.

3. The plating solution according to the invention will not deposit metal at low current densities.

4. The plating solution according to the present invention can reduce or even eliminate whiskering when the deposit is subsequently exposed to thermal conditions.

If the part to be plated is a composite article comprising a ceramic or lead glass portion, the acidic or alkaline solution will damage the ceramic or glass portion during the electroplating process. Devices such as SMT resistors, inductors, and capacitors are of this type. The pH of the electroplating solution for SMT devices should be between about 2.5 and 9 to minimize damage to the ceramic or glass portions of the article. To obtain a pH in this range, tin must be present in the form of a complex. Conventional complexing agents typically include citrate, gluconate, and pyrophosphate. In order to plate semi-gloss deposits, however, one or more organic additives are typically used. The most common additives significantly increase the low current density coverage of the solution which causes overplating of the non-conductive portion of the part and fusion of the part to be plated.

By selecting an additive that does not increase the action of the electrolyte at high metal concentrations, operate at elevated temperatures, low current density coverage (LCDC) or reduce LCDC and / or the same combination thereof, The low current density coverage can be reduced. For example, a high metal ion content of at least about 25 g / 1 is preferred when tin is the metal to be electroplated. Since it has been found that high temperatures generally increase component fusion, elevated electrolyzer temperature is the least desirable method of reducing LCDC.

The choice of organic additives in the electrolytic cell is particularly important to maintain low levels of uniform electrodeposition. The most preferred additives can be determined by conducting periodic tests on the particular plating solution desired. These additives include traditional surfactants and single or multiple aromatic rings as well as crystallization agents such as condensation compounds of organic compounds such as organic condensation or reaction products that have dye-like properties but are not surfactants. These compounds are generally known in the art to which the present invention pertains, and can be confirmed by simple experiments that do not impart high uniform electrodeposition properties to the plating solution.

Other additives may be used in combination with a surfactant and a crystal refiner to reduce the uniform electrodeposition of the electrolyte. Ammonium chloride, ascorbic acid, and M-nitrophenol are known to reduce homogeneous electrodeposition when used in combination with various surfactants and crystal refiners. Clearly, many other additives will function in this way and these other additives become a subject of the present invention. Those skilled in the art will be able to conduct routine tests to determine the best combination of additives to use or not to use any particular electroplating solution.

When plating composites, the solution according to the invention can be used in the equipment disclosed in US Pat. No. 6,193,858 and published International Patent Application WO 02/053809. Plating solutions according to the present invention can also be used in the rotary plating apparatus disclosed in US Pat. Nos. 5,487,824 and 5,565,079, with improved results, in which tin deposition on the current supply ring is substantially reduced, replacing the current feeder and wearing out. This results in a significant reduction in the maintenance required for the service.

Therefore, the use of electrolytes with reduced LCDC in spin plating apparatus is also a subject of the present invention. It would also be desirable to use the present invention when using plating barrels, since less metal will be deposited on the dangler and metal creep and part fusion will be reduced. Therefore, the use of LCDC electrolytes in barrel plating is also a subject of the present invention.

Although the present invention is particularly desirable when plating composite articles without media, using the present invention for plating discrete articles mixed with media reduces plating on the current supply and on the non-conductive portion of the composite article. This has a significant advantage in reducing or eliminating metal deposits.

A useful way to test the electrolyte with respect to LCDC is to use the standard 265 ml hull cell test. Standard procedures for operating the hull cell are used. Typical conditions would be 1 A for 5 minutes, 0.5 A for 5 minutes or 0.25 A for 5 minutes, respectively, using paddle stirring. The hull cell panel manufactured at 1A has an LCDC if the back of the hull cell panel is not plated much except for the portion extending less than 1 cm from the panel edge. In addition, the most preferred electrolyte will have an unplated portion on the front low current density edge. This unplated portion will be 1/8 "to 3/4" in inch width. In general, the electrolyte that results in this type of hull cell panel tends to be much less fused than the electrolyte in which the plating is significantly made at the back of the hull cell panel. The limiting current density at which metal cannot be deposited can be measured by preparing a Hull cell panel at 0.25 A and determining the current density at the edge of the metal deposit using an appropriate Hull cell panel scale.

Also, when electrolytes with LCDC are used without media in SBE devices for recent SMTs, it is common that the current supply will not be plated much with tin at the end of the plating cycle and the parts to be plated will not be fused to the current supply. Known as Conversely, if a commercially available neutral tin plating electrolyte is used to plate the SMT in the SBE without the medium, it will be appreciated that the part is trimmed within 3 minutes after the start of plating and the current supply is fully tinned. Thus, the use of tin or tin alloy electrolytes with LCDC is necessary for successful plating of SMT without media in SBE devices.

Example

The following examples illustrate useful embodiments of the present invention.

Example 1:

Pure tin electrodeposition is obtained from the following solution and under the following electroplating conditions.

Ascorbic acid 100 g / l

Tin (as methanesulfonate) 15 g / l

0.5ml / 1 surfactant

KOH-regulated pH: up to 4.05

The above solution will deposit semi-gloss tin at current densities up to 20 ASF.

Example 2:

Semi-gloss tin-lead deposits are obtained by adding 1.5 g / l of lead methane sulfonate to the solution of claim 1 and plating under the same conditions.

Ascorbic acid 100 g / 1

Tin (as methanesulfonate) 15 g / l

1.5 g / 1 of lead (as methanesulfonate)

Potassium methanesulfonic acid 40g / 1

0.5ml / 1 surfactant

KOH-regulated pH: up to 4.05

This solution will also deposit semi-gloss 90% tin at current densities up to 20 ASF.

Comparative example:

The formulation of Example 1 was used to plate the tides on 250 pieces of 8 mm diameter flat washer in 2.5 "by 4" barrels, and 140 ml of 2.5 mm diameter conductive balls. ) Was used as the medium. The rod was plated at 5 A, 6.5 V for 15 minutes. At the end of the plating cycle none of the flat washers were fused together.

The same plating cycle was performed using an electrolyte of the following formula:

Citric acid 40 g / 1

Tin (as methanesulfonate) 10 g / 1

1.5 g / l of lead (as methanesulfonate)

Potassium Methanesulfonic Acid 40 g / l

Surfactant 2.5ml / 1

KOH adjusted pH: 4.2

The rods were plated at 5A and 9V for 15 minutes at the end of the plating cycle and only 12 pieces were not coupled to each other. The remaining pieces aggregated into groups of up to 10 pieces and were difficult to separate. This example clearly shows the superiority of the solution according to the invention.

Example 3:

The following examples show that tin whiskering is reduced in deposits prepared by the electroplating solution according to the present invention compared to conventional electroplating solutions.

As noted earlier, the problem of whiskering occurs when the deposit is exposed to conditions such as those encountered when heat treated or plated parts are serviced. Whiskers can take from one week to five years to grow, in which case the whiskers can cause short circuiting or other problems. Accelerated tests were developed to determine if whiskering would occur on such deposits. In a thermal cycle test, the plated part is placed in a temperature control chamber at -55 ° C for 15 minutes, transferred to another temperature chamber within 20 seconds, and exposed to a temperature of 125 ° C for another 15 minutes there. This cycle is repeated 500 times to see if whiskers are produced on the deposit.

The substrate is plated with tin together with the solution of Example 1 and subjected to the thermal cycle test described above for 500 cycles. Another substrate is plated with tin from a traditional sodium gluconate plating solution, and the plated substrate also performs the same thermal cycle test for 500 cycles.

The results are shown in Figures 1-4. In Figures 1 and 2, the surface of the parts plated according to the invention exhibits very small, very short whiskers with relatively no harm. In contrast, parts plated by the prior art exhibit longer and more whiskers, resulting in a plated article that is easier to cause short circuits, or if mechanically removed, will cause mechanical problems. . Thus, the plated deposits of the present invention are even more preferred and particularly preferred for small parts such as electronic components that require tin deposits.

Claims (12)

1. a solution for use in connection with the deposition of one or more metals on an electroplatable substrate, Water; An amount of metal ions sufficient to provide a metal deposit on the plateable substrate; A complexing agent that is an organic compound having between 4 and 18 carbon atoms, a compound comprising a 5 or 6 membered ring containing at least one oxygen atom and at least two hydroxy groups, wherein the metal is dissolved in the solution. A complexing agent present in an amount sufficient to prevent oxidation of the metal while complexing the metal so as to be complex; And, if necessary, a suitable pH adjuster to maintain the pH of the solution in the range of 2 to 10. Solutions for use in connection with the deposition of one or more metals on an electroplatable substrate. The method of claim 1, The complexing agent has the structure: Has, In the above structure, Each R is the same or different and is also hydrogen or a lower alkyl group having 1 to 3 carbon atoms, T is R, OR, or O = P (OR) _2- , Z is O = or RO-, n is 2- 4, Z can be the same or different at each occurrence in the compound, and m is 1-3, Or the complexing agent is a soluble salt having the above structure. Solutions for use in connection with the deposition of one or more metals on an electroplatable substrate. The method of claim 2, The complexing agent is ascorbic acid, isoascorbic acid, dihydroascorbic acid, glucocorbic acid, galacturonic acid, glucoronic acid, or salts thereof, or is derived from ketogluconate or heptagluconate, And in an amount of about 25 to 200 g / l Solutions for use in connection with the deposition of one or more metals on an electroplatable substrate. The method of claim 1, The metal is tin and is added to the solution as alkyl sulfonic acid tin (II), tin sulfate (II), tin chloride (II), tin ascorbate (II), or tin oxide (II), about 5 to 100 g / present in quantities between l Solutions for use in connection with the deposition of one or more metals on an electroplatable substrate. The method of claim 4, wherein Further comprising a divalent lead salt in an amount sufficient to deposit a tin-lead alloy from the solution Solutions for use in connection with the deposition of one or more metals on an electroplatable substrate. The method of claim 1, Sufficient amount of conductive salts to increase the conductivity of the solution, sufficient amount of surfactant to enhance the deposition quality and crystal structure, or one or more agents to promote anode dissolution Which includes more Solutions for use in connection with the deposition of one or more metals on an electroplatable substrate. The method of claim 6, The conductive salt is an alkali or alkali metal sulfate, sulfonate, or acetate compound and the surfactant is an alkylene oxide condensation compound and is present in an amount of about 0.01 to 20 g / l, or promotes anode dissolution. The agent to be potassium methane sulfonate, ammonium chloride or metal sulfide salt Solutions for use in connection with the deposition of one or more metals on an electroplatable substrate. The method of claim 1, The substrate is a composite article having electroplating and non-electroplating portions, wherein the pH adjusting agent is an acid or a base and the pH is electroplated onto the electroplating portion of the article without adversely affecting the non-plating portion. To be adjusted in the range of about 3.5 to 5.5 Solutions for use in connection with the deposition of one or more metals on an electroplatable substrate. The method of claim 1, Contacting the substrate with the solution of claim 1 and passing a current through the solution to provide a metal electrodeposition thereon. A method of electroplating a metal deposit on a substrate. The method of claim 1, Contacting a plurality of said articles (composite articles comprising electroplating and non-electroplating portions) with the solution of claim 1 and electroplating portions of said article without adversely affecting the non-electroplating portion of said article Passing a current through the solution to provide a metal electrodeposit on the phase A method of electroplating a metal deposit on a composite article comprising electroplatable and non-electroplated portions. The method of claim 1, Contacting the substrate with the solution of claim 1 and passing a current through the solution to provide a metal electrodeposit on the substrate while reducing or eliminating whisker formation in the deposit. A method of reducing whisker formation of metal deposits on a substrate. The method of claim 11, The substrate is a composite article comprising electroplatable and non-electroplated portions, wherein the plurality of articles are contacted with the solution to provide a reduced whisker-free or reduced whisker deposit on the electroplatable portion of the article. Further comprising the steps A method of reducing whisker formation of metal deposits on a substrate.