EP0897998A2 - Reductive nickel bath - Google Patents
Reductive nickel bath Download PDFInfo
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- EP0897998A2 EP0897998A2 EP98114391A EP98114391A EP0897998A2 EP 0897998 A2 EP0897998 A2 EP 0897998A2 EP 98114391 A EP98114391 A EP 98114391A EP 98114391 A EP98114391 A EP 98114391A EP 0897998 A2 EP0897998 A2 EP 0897998A2
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- nickel
- bath
- bath according
- stabilizer
- concentration
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/31—Coating with metals
- C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
- C23C18/34—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents
- C23C18/36—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents using hypophosphites
Definitions
- the invention relates to an aqueous, acidic, reductive depositing bath for electroless deposition of nickel.
- nickel / gold adhesion requires a nickel layer that is as pure as possible, whereby a phosphorus content of less than 10% is desirable.
- the well-known nickel baths contain the nickel to be deposited in the form of nickel sulfate or nickel chloride.
- the nickel present as a cation must be reduced for the purpose of its deposition become. This task is performed by sodium hypophoshite.
- As a complexing agent for the nickel are lemon, glycol, milk, apple, vinegar, amino vinegar, Propion, Succinic acid, ammonium, sodium, sodium hydroxyacetate, sodium citrate, Sodium glyconate, hydroxylamine sulfate and mixtures of some of these acids known.
- TU Thiourea
- Stabilizers needed. Lead, tin, arsenic and molybdenum compounds are known. However, the stabilizer reduces the deposition rate.
- a disadvantage of the known baths is that in order to achieve acceptable deposition rates, the bath must be operated at relatively high temperatures of over 90 ° C. At these temperatures, the thiourea is no longer sufficiently stable and its effects are no longer fully effective. To maintain the deposition rate, thiourea must therefore be added continuously. There is a gradual accumulation of the decomposition products of the thiourea in the bath and thus an increased deposition of sulfur in the nickel layer. This makes the deposited nickel layer less noble. This leads to an increased occurrence of corrosion after the exchange gold coating, in particular to pitting corrosion in holes in the printed circuit board. The corrosion values deteriorate with increasing bath age, since more and more thiourea has to be added in order to maintain the deposition rate.
- MTO is derived from M etal T urn - O ver. that is, all of the nickel contained in the bath can only be reacted five times until the bath must be discarded.
- the present invention is based on the object of finding a composition for a bath of the type mentioned at the outset, with which a high-quality nickel layer formation with as few foreign deposits as possible is possible over a longer lifespan of the bath with a constant deposition rate.
- the limits for the complexing agent are chosen so that at the lower limit all of the nickel can still be complexed during the concentration exceeding the upper limit would be uneconomical.
- the accelerators used according to the invention are thermally more stable and more efficient than the accelerators previously used. This enables both the concentration of the accelerator and to keep the concentration of the stabilizer lower than before. This has the advantage that fewer decomposition products are produced in the bathroom than before, especially the concentration of the accelerator and the one following it Concentration of the stabilizer can be lower from the outset than in State of the art. This not only leads to a longer lifespan, but also also for better controllability of the bathroom. First experiences show that lifetimes of up to 8 MTO are achieved with baths according to the invention become.
- the accelerator should be in 1 to 3 times the molar concentration of the stabilizer be included in the bathroom. Will the relationship between stabilizer and accelerator shifted towards the stabilizer, inhibition of Conductor edges and drill holes. If there is an excess of accelerator, it can increase Pitting corrosion occurs.
- the acidic character of the nickel bath is due to the carbon and hydroxy carboxylic acids certainly; the pH value is expedient by adding ammonia set to a value between 5 and 6.
- a certain buffer effect occurs through the complexing agent used. Over time it will Bath is becoming increasingly acidic due to the chemical process. If the pH drops too much from; so it is raised again by adding ammonia.
- Hypophosphite unfolds its reducing effect in the weakly acidic range. At a pH above 6 the reducing effect of the hypophosphite decreases. The same thing applies to a pH below 5. The hypophosphite reaches its optimum reducing effect for pH values between 4.6 and 5.5.
- the present bathroom is very well suited to printed circuit boards with a noble nickel adhesive layer with a Coating phosphorus content less than 10%.
- a subsequent one Coating the noble nickel layer with an exchange gold layer causes one Reduction of corrosion compared to a less noble one - coated with gold - Nickel layer.
- the exchange gold bath can be in a wide pH range be driven between 5.5 and 6.5.
- the bath temperature is expediently between 80 ° and 90 ° C. is preferred a temperature of 85 ° to 90 ° C. is maintained in these temperature ranges one particularly economical deposition rates.
- the accelerator is above 90 ° C increasingly decomposes and foreign atoms accumulate in the bathroom then can be deposited together with the nickel and pitting could cause.
- the nickel content is preferably between 6 and 8 g per liter of bath liquid and the concentration of the reducing agent between 25 and 35 g per liter of bath liquid.
- the stoichiometric ratio is in these concentration ranges particularly advantageous between the dissolved nickel and its reducing agent, so that there is a constant deposition rate over several MTOs.
- a mixture of milk, apple and Acetic acid used, the molar ratio is preferably about 11: 4: 1. This relationship has proven particularly beneficial in terms of complexation of ionic nickel.
- a particularly advantageous development of the invention provides that in addition a complexing agent specifically complexing the stabilizer is added. It is preferably methylglycine diacetic acid, which is preferably in a concentration ratio of 0.5 to 5 ml per liter of bath liquid is clogged. This prevents the stabilizer cation from failing and preferentially precipitates on edges or boreholes. This will make the counteracted so-called edge weakness, this means that on the edges there is no inhibition by the stabilizer that causes the nickel deposition would inhibit locally. Another advantage is that the stabilizer does not need to be consumed and replenished as quickly. By clogging the further complexing agent remarkably becomes the stability of the bath not affected. A genalt in the range mentioned is advantageous, however is not a deterioration in bathing properties due to a higher concentration to recognize.
- the preferred accelerator is N-ethyl-thiourea or benzyl-isothiourea used. These two substances are thermally stable, so that hardly any Decomposition takes place, which would necessitate subsequent dosing. By the low formation of sulfur gives you a very pure nickel layer few built-in foreign atoms, which leads to good corrosion resistance leads.
- the pH of the bath should be 5.0 and is adjusted with ammonia solution.
- the bath is operated and enabled at a temperature of 88-90 ° C a deposition rate of 15 to 21 ⁇ m per hour.
- the new accelerator especially N-ethyl thiourea
- the risk of pitting corrosion is reduced because the storage of Sulfur in the deposited nickel layer is reduced.
- Particularly advantageous affects the good adhesion of gold on the nickel layer - due to a Phosphorus content less than 10% - on printed circuit boards. You also get with these small amounts of phosphorus in the nickel layer easily solderable and bondable Nickel / gold layers on the circuit board over the entire bath age of the Nickel baths.
- a second embodiment differs from the first only in that 3 ml of methylglycine-diacetic acid is added to the nickel bath. This ensures that the stabilizer is partially complexed, which surprisingly the accumulation of lead, e.g. on a conductor edge, is reduced.
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Abstract
Description
Die Erfindung betrifft ein wässriges, saures, reduktiv abscheidendes Bad zum stromlosen Abscheiden von Nickel.The invention relates to an aqueous, acidic, reductive depositing bath for electroless deposition of nickel.
Solche Bäder sind aus Wolfgang Riedel: Funktionelle Chemische Vernickelung. Eugen G. Lenze Verlag in Saulgau/Wüett. 1989 bekannt. Eine typische Anwendung ist das stromlose Aufbringen einer Nickelschicht auf verkupferte Leiterplatten. An diese Nickelschicht in Verbindung mit einer anschließend aufzubringenden Goldschicht mittels Austauschvergoldung werden hohe Anforderungen bezüglich einer guten Lötbarkeit, guten Bondbarkeit. Korrosionsbeständigkeit und der Ausbildung planarer Pads, die für die folgende Bestückung mit Bauteilen notwendig ist, gestellt. Die chemische Nickelschicht zwischen der Kupfer- und der Goldschicht wirkt hier als eine Art Barriere, so daß moglichst kein Gold in die Kupferschicht diffundieren kann, was die Lötfähigkeit verschlechtern würde. Für eine gute Nickel/Gold-Haftung ist eine möglichst reine Nickelschicht nötig, wobei ein Phosphoranteil von unter 10 % erstrebenswert ist. Die bekannten Nickelbäder enthalten das abzuscheidende Nickel in Form von Nickelsulfat oder Nickelchlorid. Das als Hation vorliegende Nickel muß zum Zwecke seiner Abscheidung reduziert werden. Diese Aufgabe übernimmt Natriumhypophoshit. Als Komplexbildner für das Nickel sind Zitronen-, Glycol-, Milch-, Äpfel-, Essig-, Aminoessig-, Propion-, Bernsteinsäure, Ammonium-, Natrium-, Natriumhydroxyacetat, Natriumzitrat, Natriumglyconat, Hydroxylaminsulfat und Mischungen von manchen dieser Säuren bekannt. Um eine höhere Nickeiabscheiderate zu erhalten, ist im Bad ein Beschleuniger enthalten. Als Beschleuniger ist Thioharnstoff (TU) bekannt. Dieser ist thermisch jedoch nicht sonderlicn stabil. Zur Stabilisierung dieser Bäder sind Stabilisatoren nötig. Bekannt sind Blei-, Zinn-, Arsen- und Molybdänverbindungen. Der Stabilisator vermindert jedoch die Abscheiderate.Such baths are from Wolfgang Riedel: Functional chemical nickel plating. Eugen G. Lenze publishing house in Saulgau / Wüett. Known in 1989. A typical application is the electroless application of a nickel layer on copper-plated circuit boards. At this nickel layer in connection with one to be subsequently applied Gold layer by means of exchange gold plating are high requirements regarding good solderability, good bondability. Corrosion resistance and the formation of planar pads, which are necessary for the following assembly with components is posed. The chemical nickel layer between the copper and the The gold layer acts as a kind of barrier here, so that as far as possible no gold in the Copper layer can diffuse, which would deteriorate the solderability. For A good nickel / gold adhesion requires a nickel layer that is as pure as possible, whereby a phosphorus content of less than 10% is desirable. The well-known nickel baths contain the nickel to be deposited in the form of nickel sulfate or nickel chloride. The nickel present as a cation must be reduced for the purpose of its deposition become. This task is performed by sodium hypophoshite. As a complexing agent for the nickel are lemon, glycol, milk, apple, vinegar, amino vinegar, Propion, Succinic acid, ammonium, sodium, sodium hydroxyacetate, sodium citrate, Sodium glyconate, hydroxylamine sulfate and mixtures of some of these acids known. In order to obtain a higher nickel egg separation rate, there is an accelerator in the bath contain. Thiourea (TU) is known as an accelerator. This is not particularly stable thermally. To stabilize these baths are Stabilizers needed. Lead, tin, arsenic and molybdenum compounds are known. However, the stabilizer reduces the deposition rate.
Ein Nachteil der bekannten Bäder liegt darin, daß zum Erreichen von passablen Abscheideraten das Bad bei relativ hohen Temperaturen von über 90°C betrieben werden muß. Bei diesen Temperaturen ist der Thioharnstoff nicht mehr ausreichend stabil und seine Wirkung ist nicht mehr in vollem Umfang gegeben. Zur Aufrechterhaltung der Abscheiderate muß deshalb ständig Thioharnstoff nachdosiert werden. Es kommt zu einer allmählichen Anreicherung der Zersetzungsprodukte des Thioharnstoffs im Bad und somit auch zu einer vermehrten Einlagerung von Schwefel in die Nickelschicht. Dadurch wird die abgeschiedene Nickelschicht unedler. Dies führt zu einem erhöhten Auftreten von Korrosion nach der Austausch-Gold-Beschichtung, im besonderen zur Lochkorrosion in Bohrungen der Leiterplatte. Die Korrosionswerte verschlechtern sich mit zunehmendem Badalter, da immer mehr Thioharnstoff zugesetzt werden muß, um die Abscheiderate aufrechtzuerhalten. Daraus ergibt sich für das Bad nur eine Lebensdauer von ca. 5 MTO (MTO ist von Metal Turn - Over abgeleitet). d.h., daß das gesamte im Bad enthaltene Nickel nur fünfmal umgesetzt werden kann, bis das Bad verworfen werden muß.A disadvantage of the known baths is that in order to achieve acceptable deposition rates, the bath must be operated at relatively high temperatures of over 90 ° C. At these temperatures, the thiourea is no longer sufficiently stable and its effects are no longer fully effective. To maintain the deposition rate, thiourea must therefore be added continuously. There is a gradual accumulation of the decomposition products of the thiourea in the bath and thus an increased deposition of sulfur in the nickel layer. This makes the deposited nickel layer less noble. This leads to an increased occurrence of corrosion after the exchange gold coating, in particular to pitting corrosion in holes in the printed circuit board. The corrosion values deteriorate with increasing bath age, since more and more thiourea has to be added in order to maintain the deposition rate. This means that the bath only has a lifespan of approx. 5 MTO (MTO is derived from M etal T urn - O ver). that is, all of the nickel contained in the bath can only be reacted five times until the bath must be discarded.
Der vorliegenden Erfindung liegt nun die Aufgabe zugrunde, eine Zusammensetzung für ein Bad der eingangs genannten Art zu finden, mit welcher eine qualitativ hochwertige Nickelschichtbildung mit möglichst wenig Fremdeinlagerungen über eine längere Lebensdauer des Bads mit gleichbleibender Abscheiderate möglich ist.The present invention is based on the object of finding a composition for a bath of the type mentioned at the outset, with which a high-quality nickel layer formation with as few foreign deposits as possible is possible over a longer lifespan of the bath with a constant deposition rate.
Diese Aufgabe wird erfindungsgemäß durch ein Bad mit der in Anspruch 1 angegebener Zusammensetzung gelöst. Vorteilhafte Weiterbildungen der Erfindung sind Gegenstand der abhängigen Ansprüche.This object is achieved by a bath with the specified in claim 1 Composition solved. Advantageous developments of the invention are the subject of the dependent claims.
Zwischen der Konzentration des Nickelsalzes und seines Reduktionsmittels ist eine direkte Beziehung vorhanden, da das Reduktionsmittel möglichst das ganze gelöste Nickel reduzieren sollte. Eine Unterschreitung der angegebenen Untergrenze für die Nickelkonzentration im Bad führt dazu, daß die Abscheiderate zu stark abnimmt, da zu wenig Nickel zur Verfügung steht. Gleiches gilt für die Konzentration des Reduktionsmittels: Beim Unterschreiten der unteren Konzentratonsgrenze wird zu wenig Nickel reduziert und die Abscheiderate sinkt. Bei einer Überschreitung der angegebenen Obergrenze der Konzentration kommt es zu Wildabscheidungen an ungewollten Stellen, so z.B. auch am Badbehälter, und zu einer Aufsalzung des Bades durch Zersetzung des Reduktionsmittels, welche mit einer zunehmenden Viskosität verknüpft ist, welche das Abscheiden von Nickel in Bohrlöchern von Leiterolatten erschwert.There is one between the concentration of the nickel salt and its reducing agent direct relationship exists, since the reducing agent, if possible, the whole should reduce dissolved nickel. Falling below the specified lower limit for the nickel concentration in the bath leads to the deposition rate decreases significantly because there is not enough nickel available. The same applies to concentration of the reducing agent: if the concentration falls below the lower limit too little nickel is reduced and the deposition rate drops. At a The specified upper limit of the concentration is exceeded Game separations at unwanted places, e.g. also on the bath container, and too salting of the bath by decomposing the reducing agent, which with an increasing viscosity is linked to the deposition of nickel in Boreholes of printed circuit boards difficult.
Die Grenzen für den Komplexbildner sind so gewählt, daß an der Untergrenze der Konzentration noch das gesamte Nickel komplexiert werden kann, während eine Überschreitung der Obergrenze unwirtschaftlich wäre.The limits for the complexing agent are chosen so that at the lower limit all of the nickel can still be complexed during the concentration exceeding the upper limit would be uneconomical.
Die erfindungsgemäß verwendeten Beschleuniger, insbesondere das Thioharnstoffderivat, sind thermisch stabiler und effizienter als die bisher eingesetzten Beschleuniger. Dadurch ist es möglich sowohl die Konzentration des Beschleunigers als auch die Konzentration des Stabilisators geringer zu halten als bisher. Das hat den Vorteil, daß im Bad weniger Zersetzunsprodukte entstehen als bisher, zumal die Konzentration des Beschleunigers und die ihr folgende Konzentration des Stabilisators von vornherein niedriger sein können als im Stand der Technik. Das führt nicht nur zu einer längeren Lebensdauer, sondern auch zu einer besseren Beherrschbarkeit des Bades. Erste Erfahrungen zeigen, daß mit erfindungsgemäßen Bädern Lebensdauern von bis zu 8 MTO erreicht werden.The accelerators used according to the invention, in particular the thiourea derivative, are thermally more stable and more efficient than the accelerators previously used. This enables both the concentration of the accelerator and to keep the concentration of the stabilizer lower than before. This has the advantage that fewer decomposition products are produced in the bathroom than before, especially the concentration of the accelerator and the one following it Concentration of the stabilizer can be lower from the outset than in State of the art. This not only leads to a longer lifespan, but also also for better controllability of the bathroom. First experiences show that lifetimes of up to 8 MTO are achieved with baths according to the invention become.
Der Beschleuniger soll in der 1 - bis 3-fachen Molkonzentration des Stabilisators im Bad enthalten sein. Wird das Verhältnis zwischen Stabilisator und Beschleuniger zum Stabilisator hin verschoben, so kommt es vermehrt zur Inhibierung von Leiterzugkanten und Bohrlöchern. Bei einem Beschleunigerüberschuß kann vermehrt Lochkorrosion auftreten.The accelerator should be in 1 to 3 times the molar concentration of the stabilizer be included in the bathroom. Will the relationship between stabilizer and accelerator shifted towards the stabilizer, inhibition of Conductor edges and drill holes. If there is an excess of accelerator, it can increase Pitting corrosion occurs.
Der saure Charakter des Nickelbades ist durch die Carbon- und Hydroxycarbonsäuren bestimmt; der pH-Wert wird durch Hinzufügen von Ammoniak zweckmäßigerweise auf einen Wert zwischen 5 und 6 eingestellt. Eine gewisse Pufferwirkung tritt durch den verwendeten Komplexbildner ein. Im Laufe der Zeit wird das Bad bedingt durch den Chemismus zunehmend sauer. Fällt der pH-Wert zu stark ab; so wird er durch Ammoniakzugabe wieder angehoben. Hypophosphit entfaltet seine reduzierende Wirkung im schwach sauren Bereich. Bei einem pH-Wert oberhalb 6 vermindert sich die reduzierende Wirkung des Hypophosphits. Dasselbe gilt für einen pH-Wert unter 5. Das Hypophosphit erreicht seine optimale reduzierende Wirkung für pH-Werte zwischen 4,6 und 5,5. Das vorliegende Bad ist sehr gut dazu geeignet Leiterplatten mit einer edlen Nickel-Haftschicht mit einem Phosphoranteil kleiner als 10 % zu beschichten. Eine daran anschließende Überziehung der edlen Nickelschicht mit einer Austausch-Goldschicht bewirkt eine Verminderung der Korrosion gegenüber einer unedleren - mit Gold beschichteten - Nickelschicht. Das Austausch-Goldbad kann in einem großen pH-Bereich zwischen 5,5 und 6,5 gefahren werden.The acidic character of the nickel bath is due to the carbon and hydroxy carboxylic acids certainly; the pH value is expedient by adding ammonia set to a value between 5 and 6. A certain buffer effect occurs through the complexing agent used. Over time it will Bath is becoming increasingly acidic due to the chemical process. If the pH drops too much from; so it is raised again by adding ammonia. Hypophosphite unfolds its reducing effect in the weakly acidic range. At a pH above 6 the reducing effect of the hypophosphite decreases. The same thing applies to a pH below 5. The hypophosphite reaches its optimum reducing effect for pH values between 4.6 and 5.5. The present bathroom is very well suited to printed circuit boards with a noble nickel adhesive layer with a Coating phosphorus content less than 10%. A subsequent one Coating the noble nickel layer with an exchange gold layer causes one Reduction of corrosion compared to a less noble one - coated with gold - Nickel layer. The exchange gold bath can be in a wide pH range be driven between 5.5 and 6.5.
Zweckmäßigerweise iiegt die Badtemperatur zwischen 80° und 90° C. bevorzugt wird eine Temperatur von 85° bis 90° C. In diesen Temperaturbereichen erhält man besonders wirtschaftliche Abscheideraten. Oberhalb von 90°C wird der Beschleuniger vermehrt zersetzt und es reichern sich Fremdatome im Bad an die dann zusammen mit dem Nickel abgeschieden werden können und Lochkorrosion hervorrufen könnten.The bath temperature is expediently between 80 ° and 90 ° C. is preferred a temperature of 85 ° to 90 ° C. is maintained in these temperature ranges one particularly economical deposition rates. The accelerator is above 90 ° C increasingly decomposes and foreign atoms accumulate in the bathroom then can be deposited together with the nickel and pitting could cause.
Vorzugsweise liegt der Nickelgehait zwischen 6 und 8 g pro Liter Badflüssigkeit und die Konzentration des Reduktionsmittels zwischen 25 und 35 g pro Liter Badflüssigkeit. In diesen Konzentrationsbereichen ist das stöchiometrische Verhältnis zwischen dem gelösten Nickel und seinem Reduktionsmittel besonders vorteilhaft, so daß sich eine gleichbleibende Abscheiderate über mehrere MTO ergibt.The nickel content is preferably between 6 and 8 g per liter of bath liquid and the concentration of the reducing agent between 25 and 35 g per liter of bath liquid. The stoichiometric ratio is in these concentration ranges particularly advantageous between the dissolved nickel and its reducing agent, so that there is a constant deposition rate over several MTOs.
Vorteilhafterweise wird als Komplexbildner eine Mischung aus Milch-, Äpfel-und Essigsäure verwendet, dessen Molverhältnis vorzugsweise etwa 11 : 4 : 1 lautet. Dieses Verhältnis hat sich als besonders förderlich in Bezug auf die Komplexierung des ionogenen Nickels herausgestellt. Vorteilhaft entfaltet sich die Wirkung des Komplexbildners für eine Molkonzentration zwischen 0,6 und 0,8 Mol pro Liter. Für den Stabilisator ist ein Gehalt von ungefähr 1 mg pro Liter Badflüssigkeit günstig.A mixture of milk, apple and Acetic acid used, the molar ratio is preferably about 11: 4: 1. This relationship has proven particularly beneficial in terms of complexation of ionic nickel. The effect unfolds advantageously of the complexing agent for a molar concentration between 0.6 and 0.8 mol per liter. For the stabilizer there is a content of approximately 1 mg per liter of bath liquid Cheap.
Um eine Zersetzung des Stabilisators zu unterdrücken und damit einer Anreicherung des metallischen Kations des Stabilisators im Bad entgegenzuwirken, ist als eine besonders vorteilhafte Weiterbildung der Erfindung vorgesehen, daß zusätzlich ein spezifisch den Stabilisator komplexierender Komplexbildner zugesetzt ist. Vorzugsweise handelt es sich hierbei um Methylglycin-Diessigsäure, die vorzugsweise in einem Konzentrationsverhältnis von 0,5 bis 5 ml pro Liter Badflüssigkeit zugesetzt ist. Dadurch wird verhindert, daß das Kation des Stabilisators ausfällt und sich bevorzugt an Kanten oder Bohrlöcher niederschlägt. Dadurch wird der sogenannten Kantenschwäche entgegengewirkt, dies bedeutet, daß an den Kanten keine Inhibierung durch den Stabilisator stattfindet, der die Nickelabscheidung lokal hemmen würde. Ein weiterer Vorteil liegt darin, daß sich der Stabilisator nicht so schnell verbraucht und nachdosiert werden muß. Durch das Zusetzen des weiteren Komplexbildners wird verblüffenderweise die Stabilität des Bades nicht beeinträchtigt. Ein Genalt in dem genannten Bereich ist vorteilhaft, jedoch ist durch eine höhere Konzentration keine Verschlechterung der Badeigenschaften zu erkennen.To suppress decomposition of the stabilizer and thus enrichment To counteract the metallic cation of the stabilizer in the bath is as A particularly advantageous development of the invention provides that in addition a complexing agent specifically complexing the stabilizer is added. It is preferably methylglycine diacetic acid, which is preferably in a concentration ratio of 0.5 to 5 ml per liter of bath liquid is clogged. This prevents the stabilizer cation from failing and preferentially precipitates on edges or boreholes. This will make the counteracted so-called edge weakness, this means that on the edges there is no inhibition by the stabilizer that causes the nickel deposition would inhibit locally. Another advantage is that the stabilizer does not need to be consumed and replenished as quickly. By clogging the further complexing agent amazingly becomes the stability of the bath not affected. A genalt in the range mentioned is advantageous, however is not a deterioration in bathing properties due to a higher concentration to recognize.
Als bevorzugter Beschleuniger wird N-Ethyl-Thioharnstoff oder Benzyl-Isothioharnstoff verwendet. Diese beiden Stoffe sind thermisch stabil, so daß kaum eine Zersetzung stattfindet, welche eine Nachdosierung nötig machen würde. Durch die geringe Bildung von Schwefel erhält man eine sehr reine Nickelschicht mit wenig eingebauten Fremdatomen, was zu einer guten Korrosionsbeständigkeit führt.The preferred accelerator is N-ethyl-thiourea or benzyl-isothiourea used. These two substances are thermally stable, so that hardly any Decomposition takes place, which would necessitate subsequent dosing. By the low formation of sulfur gives you a very pure nickel layer few built-in foreign atoms, which leads to good corrosion resistance leads.
Ein erstes Ausführungsbeispiel für ein erfindungsgemäßes Nickelbad enthält in 1 Liter Badflüssigkeit:
- 7 g Nickel in Form eines Nickelsulfats
- 35 g Natriumhypophosphit als Reduktionsmittel
- 27 g Milchsäure 90 %ig
- 23 g Bernsteinsäure
- 6 g Essigsäure
- 2 mg Blei in Form von Bleiacetat
- 1 mg N,N'-Ethylen-Thioharnstoff
- 2 ml Methylglycindiessigsäure
- Rest ist Wasser und Ammoniak.
- 7 g of nickel in the form of a nickel sulfate
- 35 g sodium hypophosphite as a reducing agent
- 27 g lactic acid 90%
- 23 g succinic acid
- 6 g acetic acid
- 2 mg lead in the form of lead acetate
- 1 mg N, N'-ethylene thiourea
- 2 ml of methylglycinediacetic acid
- The rest is water and ammonia.
Der pH-Wert des Bades soll 5,0 betragen und wird mit Ammoniaklösung eingestellt. Das Bad wird bei einer Temperatur von 88-90° C betrieben und ermöglicht eine Abscheiderate von 15 bis 21 µm pro Stunde.The pH of the bath should be 5.0 and is adjusted with ammonia solution. The bath is operated and enabled at a temperature of 88-90 ° C a deposition rate of 15 to 21 µm per hour.
Die Vorteile und Verbesserungen gegenüber dem Stand der Technik dieses Ausführungsbeispiels sind vielfältig. So wird eine gleichbleibende Abscheiderate bis zu einem Badalter von ca. 8 MTO erzielt - was gegenüber den bekannten Bädern eine beträchtliche Steigerung bedeutet - wobei keine Wildabscheidungen stattfinden. Das Nickel wird nur an den dafür vorgesehenen Stellen abgeschieden. so wird es z.B. nicht über den Bereich des zu beschichtenden Leiterzuges hinaus auf der Leiterplatte abgeschieden. Überraschenderweise liegt der Phosphorgehalt in der Nickelschicht unter 10%. Dies läßt sich aus der Gleichmäßigkeit der Abscheiderate - bedingt durch ein abgestimmtes Beschleuniger/Stabilisator-Verhältnis zusammen mit einem abgestimmten Komplexbildner-Verhältnis - erklären. Die verringerte Mitabscheidung von Phosphor hat jedenfalls den Vorteil, daß die Haftung von Gold auf dem abgeschiedenen Nickel verbessert wird. Durch das Verwenden des neuen Beschleunigers, insbesondere N-Ethyl-Thioharnstoff, verringert sich die Gefahr von Lochkorrosion, da die Einlagerung von Schwefel in die abgeschiedene Nickelschicht verringert wird. Besonders vorteilhaft wirkt sich die gute Haftung von Gold auf der Nickelschicht - bedingt durch einen Phosphor-Anteil kleiner 10 % - auf Leiterplatten aus. Außerdem erhält man bei diesen geringen Phosphor-Anteilen in der Nickelschicht gut löt- und bondbare Nickel/Gold-Schichten auf der Leiterplatte über das gesamte Badalter des Nickelbades.The advantages and improvements over the prior art of this Embodiments are varied. So there is a constant deposition rate achieved up to a bath age of approx. 8 MTO - what compared to the known baths means a significant increase - with no game separations occur. The nickel is only deposited at the designated places. so it becomes e.g. not over the area of the conductor track to be coated deposited on the circuit board. The phosphorus content is surprisingly low in the nickel layer below 10%. This can be seen from the uniformity the separation rate - due to a coordinated accelerator / stabilizer ratio together with a coordinated complexing agent ratio - to explain. The reduced co-deposition of phosphorus has the advantage that the adhesion of gold to the deposited nickel is improved. By using the new accelerator, especially N-ethyl thiourea, the risk of pitting corrosion is reduced because the storage of Sulfur in the deposited nickel layer is reduced. Particularly advantageous affects the good adhesion of gold on the nickel layer - due to a Phosphorus content less than 10% - on printed circuit boards. You also get with these small amounts of phosphorus in the nickel layer easily solderable and bondable Nickel / gold layers on the circuit board over the entire bath age of the Nickel baths.
Ein zweites Ausführungsbeispiel unterscheidet sich vom ersten nur dadurch, daß dem Nickelbad 3 ml Methylglycin-Diessigsäure beigesetzt ist. Dadurch wird erreicht, daß der Stabilisator teilweise komplexiert wird, wodurch überraschenderweise die Anreicherung von Blei, z.B. an einer Leiterzugkante, vermindert wird.A second embodiment differs from the first only in that 3 ml of methylglycine-diacetic acid is added to the nickel bath. This ensures that the stabilizer is partially complexed, which surprisingly the accumulation of lead, e.g. on a conductor edge, is reduced.
Diese Inhibierung des Stabilisators Blei hat sonst zur Folge, daß an diesen Stellen die Abscheidung von Nickel gehemmt ist, was als Kantenfehler bezeichnet wird.This inhibition of the lead stabilizer otherwise has the consequence that at these points the deposition of nickel is inhibited, which is called edge defect becomes.
Claims (15)
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19733991A DE19733991A1 (en) | 1997-08-06 | 1997-08-06 | Reductive Ni bath |
| DE19733991 | 1997-08-06 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| EP0897998A2 true EP0897998A2 (en) | 1999-02-24 |
| EP0897998A3 EP0897998A3 (en) | 1999-05-12 |
| EP0897998B1 EP0897998B1 (en) | 2001-12-05 |
Family
ID=7838137
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP98114391A Expired - Lifetime EP0897998B1 (en) | 1997-08-06 | 1998-07-31 | Reductive nickel bath |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0897998B1 (en) |
| AT (1) | ATE210207T1 (en) |
| DE (2) | DE19733991A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19908755A1 (en) * | 1999-02-19 | 2000-08-24 | Atotech Deutschland Gmbh | Metal electrodeposition process, especially for plastic and copper surface regions of circuit boards, uses a nickel and-or cobalt reduction plating bath containing a stabilizer to prevent autocatalytic deposition |
| EP1796106A1 (en) * | 2004-09-02 | 2007-06-13 | Sekisui Chemical Co., Ltd. | Electroconductive fine particle and anisotropically electroconductive material |
| WO2013174257A1 (en) * | 2012-05-22 | 2013-11-28 | Shenzhen Byd Auto R&D Company Limited | Copper plating solution and method for preparing the same |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7803457B2 (en) | 2003-12-29 | 2010-09-28 | General Electric Company | Composite coatings for groundwall insulation, method of manufacture thereof and articles derived therefrom |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3489576A (en) * | 1966-08-04 | 1970-01-13 | Gen Motors Corp | Chemical nickel plating |
| US4483711A (en) * | 1983-06-17 | 1984-11-20 | Omi International Corporation | Aqueous electroless nickel plating bath and process |
| EP0346265A1 (en) * | 1988-06-09 | 1989-12-13 | United Technologies Corporation | Ethylenethiourea wear resistant electroless nickel-boron coating compositions |
| EP0692554A1 (en) * | 1994-07-14 | 1996-01-17 | Matsushita Electric Industrial Co., Ltd. | Electroless plating bath used for forming a wiring of a semiconductor device, and method of forming a wiring of a semiconductor device |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TW390915B (en) * | 1995-10-23 | 2000-05-21 | Uyemura C & Co Ltd | Electroless nickel plating solution and method |
-
1997
- 1997-08-06 DE DE19733991A patent/DE19733991A1/en not_active Withdrawn
-
1998
- 1998-07-31 AT AT98114391T patent/ATE210207T1/en not_active IP Right Cessation
- 1998-07-31 DE DE59802304T patent/DE59802304D1/en not_active Expired - Fee Related
- 1998-07-31 EP EP98114391A patent/EP0897998B1/en not_active Expired - Lifetime
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3489576A (en) * | 1966-08-04 | 1970-01-13 | Gen Motors Corp | Chemical nickel plating |
| US4483711A (en) * | 1983-06-17 | 1984-11-20 | Omi International Corporation | Aqueous electroless nickel plating bath and process |
| EP0346265A1 (en) * | 1988-06-09 | 1989-12-13 | United Technologies Corporation | Ethylenethiourea wear resistant electroless nickel-boron coating compositions |
| EP0692554A1 (en) * | 1994-07-14 | 1996-01-17 | Matsushita Electric Industrial Co., Ltd. | Electroless plating bath used for forming a wiring of a semiconductor device, and method of forming a wiring of a semiconductor device |
Non-Patent Citations (1)
| Title |
|---|
| KEPING H ET AL: "A SUPER HIGH SPEED ELECTROLESS NICKEL PLATING PROCESS" TRANSACTIONS OF THE INSTITUTE OF METAL FINISHING, Bd. 74, Nr. PART 03, 1. Mai 1996, Seiten 91-94, XP000594644 * |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19908755A1 (en) * | 1999-02-19 | 2000-08-24 | Atotech Deutschland Gmbh | Metal electrodeposition process, especially for plastic and copper surface regions of circuit boards, uses a nickel and-or cobalt reduction plating bath containing a stabilizer to prevent autocatalytic deposition |
| EP1796106A1 (en) * | 2004-09-02 | 2007-06-13 | Sekisui Chemical Co., Ltd. | Electroconductive fine particle and anisotropically electroconductive material |
| EP1796106A4 (en) * | 2004-09-02 | 2010-04-14 | Sekisui Chemical Co Ltd | Electroconductive fine particle and anisotropically electroconductive material |
| WO2013174257A1 (en) * | 2012-05-22 | 2013-11-28 | Shenzhen Byd Auto R&D Company Limited | Copper plating solution and method for preparing the same |
| US9017463B2 (en) | 2012-05-22 | 2015-04-28 | Byd Company Limited | Copper plating solution and method for preparing the same |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0897998B1 (en) | 2001-12-05 |
| DE19733991A1 (en) | 1999-02-11 |
| DE59802304D1 (en) | 2002-01-17 |
| ATE210207T1 (en) | 2001-12-15 |
| EP0897998A3 (en) | 1999-05-12 |
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