KR20080024525A - Tin electrodeposits having properties or characteristics that minimize tin whisker growth - Google Patents

Abstract

A tin deposit which is inherently less prone to tin whisker formation or growth is obtained by one or more of: (i) the deposition of a fine-grained tin deposit having an average grain diameter in the range of 0.05 to 5 microns; (ii) a phosphorous compound in the solution that is used to electroplate the tin deposit so that that the deposit incorporates trace amounts of phosphorous which reduces tin whisker formation by preventing surface oxides even when exposed to heat or humidity; or (iii) a phosphorous, mercaptan or organic compound in a solution that applies a protective coating to the surface of a previously electroplated tin deposit, wherein the protective coating acts to minimize or prevent oxide formation or corrosion of the tin deposit during exposure to heat or humidity. Such tin deposits containing 80% to 100% by weight of tin exhibit minimal to no tin whisker growth. ® KIPO & WIPO 2008

Description

Tin electrodeposition with properties or properties that minimize tin whisker growth {TIN ELECTRODEPOSITS HAVING PROPERTIES OR CHARACTERISTICS THAT MINIMIZE TIN WHISKER GROWTH}

The present invention relates to methods of depositing tin in a manner that reduces, minimizes or prevents tin whisker growth from tin deposits, as well as electroplated parts formed by such methods. More particularly, the present invention relates to modifications or treatments of deposits that render them not prone to whisker growth. In particular, the formation of oxides and / or corrosion reactions on tin deposit surfaces or the post-treatment of deposit surfaces has been found to be effective for this purpose.

The use of tin or tin alloy electroplated deposits is becoming increasingly important in the manufacture of electronic circuits, electronic devices and electrical connectors because of the advantages that such deposits provide. For example, tin and tin alloy deposits protect components from corrosion, provide a chemically stable surface for soldering, and maintain good surface electrical contacts. There are many patents that disclose methods of applying tin or tin alloy deposits using various plating solutions and plating methods. Such deposits are typically produced by electroless plating or electroplating.

Regardless of the deposition process used, it is desirable to form flat, homogeneous tin deposits on the substrate to minimize porosity. It is also desirable to form a coating with a relatively constant thickness to facilitate downstream component assembly operations. Moreover, other problems must be avoided to obtain proper deposits. When pure tin is used and applied to a copper or copper alloy substrate, the resulting deposit undergoes intermolecular diffusion of base material copper into the tin deposit and subsequent formation of copper-tin intermetallic compounds. These copper-tin compounds are brittle and can impair the utility of tin coated parts, the presence of which also results in compressive stress formation in tin deposits. In turn, the generation of metal filaments known as tin whiskers sometimes spontaneously grow from these tin deposits. These whiskers are hairy protrusions extending from the surfaces and may be straight, curly, or bent. Tin whiskers typically have a diameter of about 6 nanometers to 6 microns. The presence of these whiskers is undesirable because of the very fine line resolution required for modem circuitry because these whiskers can form both electrical shorts and electrical bridges across the insulating spaces between the conductors. Whiskers can create shorts or fail in electronic circuits.

The mechanism of tin whisker growth is not fully understood. Whiskers start to grow within a few days or even years after applying the coating. There is a review of the literature that grows from compressive stress concentration sites such as those produced through many electrodeposition techniques and / or storage conditions. There is evidence that elevated temperature and humidity storage conditions enhance whisker growth. The literature ("Simultaneous Growth of Whiskers on Tin Coatings: 20 Years of Observation", SC Britain, Transactions of the Institute of Metal Finishing, Volume 52, 1974, 95-102) discusses the problem of tin whisker growth and the risk of whisker formation. It provides several recommendations to reduce the risk.

One attempt to address the tin whisker problem specifies a short storage time for tin plated materials. However, these attempts do not fully address or necessarily avoid the problem. Another attempt is to strengthen the tin matrix slightly to prevent the whiskers from extruding. The formation of intermetallic compounds and the diffusion of copper into the tin deposits are used for this purpose, but at very high performance cost in the final product.

Another attempt is to treat the surface of the substrate before applying the tin deposit. Ultrasonic shaking of the plating solution and / or polarity replacement of the electrodes during plating is proposed to reduce the amount of hydrogen absorbed or occluded in the structure of the plating metal.

Other attempts to address this problem generally involve adding a whisker suppression element to the tin plating solution. In order to avoid high cost precious metals, the most common attempt is to deposit alloys of tin and lead. Such alloys may also be compatible with the solders used later to enable electrical connection to wires or other electrical components. Unfortunately, lead and many other alloying elements are undesirable due to their toxicity and related environmental issues. Thus, pure tin or very high contents of deposits are currently used and they are subjected to whiskering under certain conditions. This is a significant problem for small electronic components with tin deposits, as short circuits can lead to.

BZ li and DN li are described in “Spontaneous Growth Mechanism of Tin Whiskers”, appearing in Acta mater. Vol. 46, No. 10, 1998, 3701-3714. First, the driving force for tin whisker growth is the tin deposit / copper substrate. The point of compressive stress formed by intermetallic compound formation at the interface has been clarified. In turn, this increase in compressive stress is due to diffusion of copper from the base material into the tin deposit and subsequent formation of copper-tin intermetallic compounds; It is theorized that concomitant volumetric deformations that occur again generate compressive stresses that lead to tin whisker formation. Several methods have been developed to deal with tin whisker growth resulting from this origin. In US Pat. No. 6,860,981, Schetty et al. Disclose a method of depositing tin in a preferred crystal orientation that matches a substrate that alternately minimizes tin whisker growth. Schetty in U.S. Non-Patent Application 11 / ***, ***, filed June 23, 2006, claiming priority of Provisional Patent Application 60 / 693,701, filed June 24, 2005. Discloses a method of using silver as a barrier layer for minimizing copper-tin intermetallic compound formation, while in US 2002/0187364 A1, Egli et al. Described a thin layer barrier of nickel or cobalt to minimize tin whisker growth. A method of using is disclosed.

In May 2005, the electronic industry standardization organization JEDEC issued JEDEC STANDARD JESD22A121 "Measuring Whisker Growth on Tin and Tin Alloy Surface Finishes", which disclosed three methods for testing tin whisker growth, two of which were rising. Use heat and / or moisture. It has recently been found that other driving forces for tin whisker growth occur when certain corrosion reactions and / or tin oxide formation occurs on the surface of electroplated tin deposits that are subjected to elevated heat and / or moisture conditions over an extended period of time. Was decided on.

For example, three papers were submitted on this subject at the iNEMI Tin Whisker Workshop on 1 June 2005 in Orlando, Florida, United States. "Humidity Effects on Sn Whisker Formation" by Marc Dittes, Infineon et al .; Dr. Freescale Semiconductor Peng Su, “A Statistical Study of Sn Whisker Population and Growth during Elevated Temperature / Humidity Storage Test”; And Agere's J. Osenbach's "Sn Corrosion and its Influence on Whiskers" all disclose this recently discovered new mechanism of tin whisker growth. The following is an abstract of these papers.

In particular, when exposed to heat & moisture, tin is converted to tin oxide, which in turn results in localized compressive stress (due to localized volume increase) and / or tin whisker growth, as shown in the drawings of the Dittes paper. It can lead to corrosion reactions due to water condensation associated with exposed base materials that form galvanic couples that induce compressive stresses that become the driving force for them.

It may be highly desirable to identify a series or a counter-acting method or methods of events disclosed in the paragraph above. This problem is not addressed today in the industry where most companies dealing with tin whisker growth do not consider or solve this newly developed drive for tin whisker growth. It may also be advantageous to identify a method of preventing and / or minimizing the occurrence of tin oxidation and / or corrosion reactions on the tin deposit during exposure to high thermal and moisture conditions. The present invention currently provides such methods.

Summary of the Invention

The present invention is directed to a number of methods for reducing tin whisker formation or growth in tin deposits on a substrate. In general, at least one property or property of the tin deposit is modified during or immediately after the deposition of the same on the substrate. Accordingly, tin deposits are provided on substrates having at least one property or property that makes tin whiskers less prone to formation or growth such that tin whiskering is substantially reduced or even prevented.

In one embodiment, the tin deposit may be provided on the substrate as a fine particle structure that minimizes tin whiskering, where the tin deposit preferably has an average particle size of about 0.05 to 5, preferably about 2 to 3 microns. Have

In other embodiments, tin deposits may be processed during deposition to reduce the tendency for tin whisker formation or growth. This can be done by allowing tin deposits that are essentially free of surface oxides to minimize tin whiskering thereon. Prevention of surface oxide formation is conveniently accomplished by providing tin deposits from solutions containing phosphorus compounds, thereby incorporating trace amounts or small amounts of phosphorus into the tin deposits. Preferably, the tin plating solution contains sufficient phosphorus compound to provide phosphorus in an amount of about 0.1 ppm to 30% by weight in the tin deposit.

In another embodiment of this method, the tin deposit is treated after deposition to have a less tendency for tin whisker formation or growth. One way to achieve this is to apply a protective coating on the tin deposit (ie, after the tin plating is complete). To do this, the tin deposit can be immersed in or contacted with a post-treatment solution containing one or more of phosphorus compounds, organic compounds, mercaptans, or organo-metal compounds. Conveniently, this protective coating is applied at a thickness of about 0.1 Angstroms to 1 micron.

The present invention also relates to the improvement of tin plated electronic components that include a copper surface on which tin deposits of fine particle size are present. This improvement includes: (a) fine grain structures such that tin deposits have less tendency to tin whisker formation or growth compared to tin deposits with larger grain structures; (b) tin deposits are essentially free of surface oxidation and have traces or small amounts of phosphorus such that they have less tendency to whisker formation or growth as compared to tin deposits having surface oxidation; Or (c) minimizing or preventing tin whisker formation or growth by providing the tin deposit with one or more of the protective layers that are less prone to tin whisker formation or growth as compared to tin deposits without any protective layer. do.

desirable Of embodiments  details

The present invention is directed to producing tin deposits that are inherently less prone to oxide formation and / or corrosion reactions on the tin deposit surfaces through the use of one or more methods of reducing whisker formation in the tin deposits on the substrate. One method includes: (i) deposition of "fine-grained" tin deposits having an average particle diameter in the range of 0.05 to 5 microns, for example particle diameters that inherently result in tin deposition that is less prone to surface oxidation; (ii) the use of phosphorus compounds in solutions used to deposit tin deposits on substrates incorporating trace amounts of phosphorus in tin deposits which again reduces tin oxide formation on the surface during exposure to heat and / or moisture; And / or (iii) the use of phosphorus compound, organic, mercaptan, and / or organo-metal compound (s) in solution (s) used to apply a protective coating to the surface of the previously deposited electroplated tin deposit. Producing a tin deposit that is inherently less prone to oxide formation and / or corrosion reactions on the tin deposit surface, wherein the protective coating is corroded to the oxide formation and / or tin deposit during exposure to heat and / or moisture. To minimize or prevent it; All of these, alone or in combination, minimize tin whisker growth of tin deposits.

The invention also relates to a plated substrate comprising a tin deposit having reduced surface oxidation and / or corrosion properties in the layer comprising tin. The layer comprising tin preferably contains no more than 80% by weight, preferably even higher amounts of tin, without experiencing significant whiskering. Inherently homogeneous deposits of pure tin (ie, tin containing no other elements except incidental impurities and no intentionally added alloying elements) can be deposited without experiencing significant whiskering problems. have. Thus, the substrate may be an electronic component comprising portions that may not be electroplated and electroplatable portions to be plated. In a preferred embodiment, the tin content of the deposit is at least 80% and 100% by weight of the deposit. If desired, alloying elements may be added to the solution used to deposit tin to provide a deposit of the tin alloy.

Tin plating solutions useful in the present invention include, but are not limited to, those disclosed below:

FLUOBORATE SOLUTIONS: Tin fluoroborate plating baths are widely used to plate all types of metal substrates including both copper and iron. See, for example, US Pat. Nos. 5,431,805, 4,029,556, and 3,770,599. These baths are preferred where the rate of plating is important and the fluoroborate salts are very soluble.

HALIDE SOLUTIONS: Tin plating baths with major electrolytes that are halide ions (Br, Cl, F, I) have been used for decades. See, for example, US Pat. Nos. 5,628,893 and 5,538,617. The primary halide ions in these baths were chloride and fluoride.

SULFATE SOLUTIONS: Tin and tin alloys are commercially plated from solutions with sulfates as primary anions. See, for example, US Pat. Nos. 4,347,107, 4,331,518 and 3,616,306. For example, the steel industry has tinned steel for years from sulfuric acid / tin sulfate sulfate baths in which phenol sulfonic acid is used as a special electrolyte additive to improve the oxidation stability of tin as well as increase its current density range. Such a process, known as a ferrostan process, can be used in the present invention, but is not preferred because of the environmental problems with phenol derivatives. Other sulfate baths based on sulfuric acid but free of environmentally undesirable additives are preferred.

SULFONIC ACID SOLUTIONS: Over the past two decades, the commercial use of sulfonic acid metal plating baths has increased considerably due to many performance advantages. Tin was electroplated from sulfonic acid (eg, US Pat. Nos. 6,132,348, 4,701,244 and 4,459,185). The unit cost of alkyl sulfonic acids is relatively high, so the preferred sulfonic acid used is methane sulfonic acid (MSA), although the prior art includes examples of other alkyl and alkanol sulfonic acids. Performance advantages of alkyl sulfonic acid baths include low corrosiveness, high solubility of salts, good conductivity, good oxidation stability of tin salts and complete biodegradability.

These solutions can be used alone or in various mixtures. One of ordinary skill in the art can select the most preferred acid or acid mixture for any particular plating application.

The amount of tin (as tin metal) in the plating solutions of the present invention can vary over a wide range up to about 1 to about 120 g (g / l) metal per liter of solution or to the solubility limit of a particular tin salt in a particular solution. . Although the above amount of tin in the plating solution has been disclosed as metallic tin, it should be understood that tin can be added to the solution in the form of tin compounds. Such compounds are, for example, tin oxide, tin salts, or other soluble tin compounds, such as formates, acetates, sulfates, alkane sulfonates, hydrochlorides and other halides, carbonates And the like.

Various surfactants and humectants can be used if desired. Surfactants are selected to achieve the desired deposit qualities and properties. Examples illustrate commercially available baths containing preferred surfactants and / or humectants to provide the preferred tin deposits according to the present invention. Any of the surfactants mentioned in US Pat. No. 6,860,981 can be used, which is incorporated herein by reference for the disclosure of such components. In addition, any tin or tin-derived surfactants generally known in the art (eg, block copolymers, alkylene oxides, polyalkylene glycols, ENSA, nonyl-phenol ethoxylate 8-) 14 mole ethylene oxide, etc.) can all be used, but when fine particle size deposits are desired, secondary particle refiners are generally used in combination with the surfactant (s).

Any of many alloying elements can be added to the tin plating solution. They are mainly added in an amount such that less than 5% of the alloying elements are present in the deposit. Preferred alloying elements include silver (up to 3.5% of the deposit), bismuth (up to 3% of the deposit), copper (up to 3% of the deposit) and zinc (up to 2% of the deposit). Other alloying elements may be used, but it is generally preferred not to use those which may have adverse effects on the environment, namely antimony, cadmium, and especially lead. Preferably, as mentioned above, the alloying elements are optional and the tin content of the deposit is as high as possible and dimensionally high, at least 99% by weight, in balance with the inevitable impurities.

In the first method of the present invention, tin whisker growth is prevented or at least substantially minimized by depositing fine-grained tin deposits having an average particle diameter of 0.05 to 5 microns. More preferred particle diameters are 1 to 3 microns. Any tin electroplating solution that can produce an average particle diameter in this range can be used, but those disclosed in US Pat. No. 6,860,981 as described above are preferred. As mentioned above, secondary particle refiners are used to ensure that fine particle structures are obtained in deposits. Biquinoline and dimethyl-phenanthroline additives are preferred secondary particle refiners that reduce particle size, although other materials, especially as known to those skilled in the art, may be used to achieve the same result.

In order to confirm that the desired particle size is achieved, it is usually measured by scanning electron microscopy (SEM) at 2000X and 5000X magnifications, by photographs having a scale thereon to measure the particle diameter of many particles of the tin deposit. The average of the measurements is taken to determine the particle size. What differs from the prior art in the present invention is the fact that SEM measurements are used to confirm that the particle size is within the preferred range. Fine grain structures of this type can occur in some of the prior art baths, but can occur purely by accident and in unintended ways. In the present invention, the presence of fine particle structures is identified to obtain the desired reduction or removal of tin whiskering.

Tin deposits of varying particle size were exposed to high heat & moisture conditions to deliberately promote tin oxide formation, which was subsequently analyzed by surface electrochemical reduction analysis ("SERA"). Fine-grained tin deposits (average particle diameters from 0.05 to 3 microns) were compared to conventional larger particle diameter tin deposits (average particle diameters from about 3 to 8 microns), resulting in lower thicknesses on the surface. Produces tin oxide constantly. This phenomenon shows that micro-particle tin deposits generally have a smoother surface structure, and therefore generally show less exposed microscope "peaks" and "curves" as compared to large, coarse-grained tin deposits. This is due to the fact that smaller exposed surface areas for oxidation / corrosion reactions occur on fine particle size tin deposits as compared to large particle size tin deposits. In addition, many particle boundaries of the fine particle size structure act as a stress distribution or stress relaxation network to prevent the compressive stress on the deposit from concentrating and generating tin whiskers.

In another method of the present invention, the use of phosphorus compounds in a solution used to deposit tin deposits on a substrate, thereby incorporating trace amounts of phosphorus into the tin deposits, results in a surface during exposure to heat and / or moisture. The tin oxide formation on the phase is again reduced. Preferred solutions and amounts to be added are disclosed in US Pat. No. 6,982,030 to Zhang et al., Which considers the use of such additives in the context of improved deposit soldering potential. With the new knowledge currently obtained in the art regarding the effect of tin oxide formation on tin whisker growth after exposure to high heat and moisture conditions, the method disclosed in the patent not only minimizes tin whisker growth but also It has now been found to disclose that deposits can be used to provide the advantage of reducing surface oxidation when provided under conditions already disclosed.

In another method of the invention, the use of one or more of the phosphorus compounds, organic, and / or organo-metallic compounds in solution minimizes corrosion of oxide formation and / or tin deposits during exposure to heat and / or moisture, or It is used to apply a protective coating to the surface of a tin deposit already electroplated by a protective coating that acts to prevent it. Available from Technic, Inc., RI Cranston; product Tarniban, Tarniban 51, Tarniban E260 are all examples of solutions containing such additives; In addition, the Examples section that follows identifies other useful specific compounds for this purpose. This “post-treatment” process effectively applies a thin film (0.5 angstroms to 0.5 microns thick) to the surface of the deposited tin deposit, thereby minimizing negative reactions resulting from oxidation and / or corrosion, all of which are currently It is known to be the driving force for tin whiskers during exposure to high heat and moisture.

The following examples illustrate the most preferred embodiments of the invention.

Example 1 (Comparative Example): Cu alloy at a sufficient current density of 150 A / ft ² for the time to obtain a deposition thickness of the tin tin average 10㎛ substrate (Cu99.85%, Sn0.15%) onto MSA electrolyte ( Electroplated from "Solderon ST300", Rohm & Haas. The particle size of the tin deposit was measured and found to be an average particle size diameter of 5-8 microns. This deposit was subjected to a high temperature and humidity (HTH) test of 155 ° C. for 16 hours (in an unregulated humidity environment) and then to 97 ° C./99% relative humidity (RH) for 8 hours. This deposit was measured by SERA and the tin oxide thickness on the surface was found to be 122 Angstroms. These deposits were subjected to the high temperature & humidity whisker test conditions specified by JEDEC STANDARD JESD22A121 "Measuring Whisker Growth on Tin and Tin Alloy Surface Finishes", in particular: stored at a high temperature / humidity of 60 ° C./90% RH for 3000 hours. do. As the whisker test method was completed, the maximum whisker length was measured and determined to be 112 μm.

Example 2 Tin was mixed with a mixed acid sulfate electrolyte ("Technistan") onto a Cu alloy substrate (Cu99.85%, Sn0.15%) at a current density of 150 A / ft ² for a time sufficient to obtain a tin deposit thickness of 10 μm on average. EP ", Technic Inc.). The particle size of the tin deposit was measured and found to be an average particle size diameter of 1-2 microns. This deposit was subjected to a high temperature and humidity (HTH) test of 155 ° C. for 16 hours (in an unregulated humidity environment) and then to 97 ° C./99% relative humidity (RH) for 8 hours. This deposit was measured by SERA and the tin oxide thickness on the surface was found to be 68 Angstroms. These deposits were subjected to the high temperature & humidity whisker test conditions specified by JEDEC STANDARD JESD22A121 "Measuring Whisker Growth on Tin and Tin Alloy Surface Finishes", in particular: stored at a high temperature / humidity of 60 ° C./90% RH for 3000 hours. do. As the whisker test method was completed, the maximum whisker length was measured and determined to be 55 μm.

Example 3: sufficient time mixed acid sulfate electrolyte with a 150 A / Cu alloy substrate at a current density of ^{ft 2 (Cu99.85%, Sn0.15%} ) during the obtaining the tin deposition thickness of the tin average 10㎛ (US Pat. Electroplated from "Technistan EP", Technic Inc., which also contains phosphorus compounds at a concentration of 4 g / l in the plating solution as disclosed in application 2004/0099340 A1. The particle size of the tin deposit was measured and found to be an average particle size diameter of 1-2 microns. This deposit was subjected to a high temperature and humidity (HTH) test of 155 ° C. for 16 hours (in an unregulated humidity environment) and then to 97 ° C./99% relative humidity (RH) for 8 hours. This deposit was measured by SERA and the tin oxide thickness on the surface was found to be 43 Angstroms. These deposits were subjected to the high temperature & humidity whisker test conditions specified by JEDEC STANDARD JESD22A121 "Measuring Whisker Growth on Tin and Tin Alloy Surface Finishes", in particular: stored at a high temperature / humidity of 60 ° C./90% RH for 3000 hours. do. As the whisker test method was completed, the maximum whisker length was measured and determined to be 43 μm.

Example 4: a sufficient time mixed acid sulfate electrolyte with a 150 A / Cu alloy substrate at a current density of ^{ft 2 (Cu99.85%, Sn0.15%} ) during the obtaining the tin deposition thickness of the tin average 10㎛ (US Pat. Electroplated from "Technistan EP", Technic Inc., which also contains phosphorus compounds at a concentration of 4 g / l in the plating solution as disclosed in application 2004/0099340 A1. After tin plating, the substrate was placed at 50 g / l into a solution containing phosphorus compound (phosphate @ 70 ml / l) + sodium gluconate. The particle size of the tin deposit was measured and found to be an average particle size diameter of 1-2 microns. This deposit was subjected to a high temperature and humidity (HTH) test of 155 ° C. for 16 hours (in an unregulated humidity environment) and then to 97 ° C./99% relative humidity (RH) for 8 hours. This deposit was measured by SERA and the tin oxide thickness on the surface was found to be 35 Angstroms. These deposits were subjected to the high temperature & humidity whisker test conditions specified by JEDEC STANDARD JESD22A121 "Measuring Whisker Growth on Tin and Tin Alloy Surface Finishes", in particular: stored at a high temperature / humidity of 60 ° C./90% RH for 3000 hours. do. As the whisker test method was completed, the maximum whisker length was measured and determined to be 38 μm.

Example 5 : Tin was mixed with a mixed acid sulfate electrolyte ("Technistan") onto a Cu alloy substrate (Cu99.85%, Sn0.15%) at a current density of 150 A / ft ² for a time sufficient to obtain an average deposit thickness of 10 μm. EP ", Technic Inc.). After tinning the substrate, the substrate contains 10 ml / l of solvent (butyl cellosolve), 10 ml / l of surfactant (Jeffox WL4000), and 4 g / l of mercaptopropionic acid at 40 ° C. for 30 seconds. Placed into solution. The particle size of the tin deposit was measured and found to be an average particle size diameter of 1-2 microns. These deposits were subjected to the high temperature & humidity whisker test conditions specified by JEDEC STANDARD JESD22A121 "Measuring Whisker Growth on Tin and Tin Alloy Surface Finishes", in particular: stored at a high temperature / humidity of 60 ° C./90% RH for 3000 hours. do. As the whisker test method was completed, the maximum whisker length was measured and determined to be 33 μm.

These embodiments illustrate the following advantages of the present invention. Example 1 shows the results from standard large particle size tin deposits commonly used in the art, where (i) tin oxide formation is very high after heat & humidity exposure at 122 Angstroms, and (ii) after JEDEC processing. The corresponding tin whisker growth is excessive at 122 microns; Although no industry standard yet exists for the maximum allowable whisker length, it is common to consider 50 microns.

Example 2 shows that (i) tin oxide formation is significantly reduced compared to conventional large particle size deposits from Example 1 after heat & humidity exposure at 68 Angstroms, and (ii) the corresponding tin whisker growth after JEDEC process is 55 Showing the results of the present invention including micro-grained tin deposits, which show a significant reduction from Example 1 in comparison with conventional large particle size deposits in microns, as evidence that the corrosion / oxidation protection enhancing effect of the present invention is a tin whisker growth It is extremely effective in his ability to minimize it.

Example 3 shows that (i) tin oxide formation is significantly reduced from conventional large particle deposits from Example 1 after heat & humidity exposure at 43 Angstroms, and further reduced compared to the deposits of Example 2 above. (Ii) showing the results of the present invention comprising a fine-grained tin deposit in combination with a phosphorus-containing additive in the plating solution showing that the corresponding tin whisker growth after the JEDEC process is significantly reduced at 43 microns, and As evidence, the corrosion / oxidation protection enhancing effect of the present invention is extremely effective in its ability to minimize tin whisker growth.

Example 4 further shows that (i) tin oxide formation is significantly reduced compared to conventional large particle deposits from Example 1 after heat & humidity exposure at 35 angstroms, and in addition to the deposits of Examples 2 & 3 above. Reduced to (ii) the corresponding tin whisker growth after the JEDEC process shows a result of the present invention comprising a fine-grained tin deposit in combination with a phosphorus-containing post-treatment solution, which shows a significant reduction at 38 microns, Evidence shows that the corrosion / oxidation protection enhancing effect of the present invention is extremely effective in its ability to minimize tin whisker growth.

Example 5 shows the results of the present invention comprising a fine-grained tin deposit in combination with an organic-containing post-treatment solution showing that the corresponding tin whisker growth is significantly reduced at 33 microns after the JEDEC process. The corrosion / oxidation protection enhancing effect of the present invention is extremely effective in its ability to minimize tin whisker growth.

Claims (20)

Electroplating the tin deposit on the electroplatable substrate and modifying at least one physical property or property of the tin deposit sufficiently over time to lessen the whisker growth tendency of the deposit or to prevent tin whisker formation. And wherein the modifying step occurs during or after depositing the tin deposit on the substrate. The method of claim 1, wherein the physical properties or properties are modified when the tin deposit is electroplated onto the substrate to prevent or lessen the formation or growth of tin whiskers in the deposit. The method of claim 2, wherein the modified physical property or property is its particle structure and the tin deposit has a fine particle structure. The method of claim 3, wherein the tin deposit has an average particle size of about 0.05 to 5 microns. The method of claim 2, wherein the modified physical property or property is its surface oxidation and the tin deposit is essentially free of surface oxides when deposited. The method of claim 5, wherein the surface oxide formation on the tin deposit is reduced or prevented by depositing the tin deposit from a solution containing a phosphorus compound such that trace amounts or small amounts of phosphorus are incorporated into the tin deposit to expose the deposit to heat or moisture. Resist surface oxide formation even when The method of claim 6, wherein the solution contains sufficient phosphorus compound to provide phosphorus in an amount of about 0.1 ppm to 30% by weight in the tin deposit. The method of claim 1, wherein the tin deposit is treated after deposition to reduce the tendency of tin whisker growth. The method of claim 8, wherein the tin deposit is treated by applying a protective coating thereon. 10. The method of claim 9, wherein the tin deposit is immersed in or in contact with a post-treatment solution containing one or more of phosphorus compounds, mercaptan compounds, or organic or organo-metal compounds to apply a protective coating thereon. How to be. The method of claim 1, wherein the protective coating is applied at a thickness of about 0.1 Angstroms to 1 micron. The method of claim 1, wherein the tin deposit comprises at least 80 wt% to 100 wt% tin and the substrate is an electrical component. The method of claim 12, wherein the substrate is an electronic component comprising electroplatable portions and non-electroplatable portions, and the tin deposit is provided on the electroplatable portions. The method of claim 1, wherein the substrate comprises copper. (a) a fine grain structure in which the tin deposit has a less tendency to tin whisker formation or growth compared to tin deposits having larger grain structures; (b) tin deposits are essentially free of surface oxidation and have traces or small amounts of phosphorus such that they have less tendency to whisker formation or growth as compared to tin deposits having surface oxidation; or (c) improvements to minimize or prevent tin whisker formation or growth by providing the tin deposit with one or more of the protective layers that are less prone to tin whisker formation or growth as compared to tin deposits without any protective layer. A tin plated electronic component comprising a copper surface provided with a fine particle tin deposit. The tin deposit has a fine grain structure having an average particle size of about 0.05 to 5 microns so that the tin deposit has a less tendency for tin whisker formation or growth as compared to tin deposits having a larger grain structure. The tin-plated electronic component having. 16. The trace deposit of claim 15 wherein the tin deposit is essentially free of surface oxidation even when the deposit is exposed to heat or moisture and has a lesser amount of trace or small amount of whisker formation or growth than tin deposits having surface oxidation. A tin plated electronic component having phosphorus. 18. The tin plated electronic component of claim 17, wherein the phosphorus is present in the tin deposit in an amount of about 0.1 ppm to 30 weight percent. The method of claim 15, wherein the tin deposit has a protective layer such that tin whisker formation or growth tends to be less as compared to tin deposits without any protective layer, the protective layer being a phosphorus compound, a mercaptan compound, or an organic or A tinned electronic component provided by being immersed in or in contact with a post-treatment solution containing at least one of the organo-metallic compounds. 20. The tinned electronic component of claim 19, wherein the protective coating is present from about 0.1 Angstroms to 1 micron thick.