化学镀镍/浸金的状况ENIG Introduction作为PCB的表面镀层，镍层的厚度要求>5um，而浸金层厚度在0.05-0.15um 之间。

化学镀镍/浸金镀层的焊接性是由Ni层来体现的，因此Au层的厚度不能太高，否则会产生脆性和焊点不牢的故障。

Au只起保护Ni层的作用，防止Ni 的氧化和渗析，所以又不能太薄。

As one of the surface finishing for PCB, the thickness of nickel layer shall be more than 5um, while the thickness of immersion gold shall be between 0.05-0.15 um.As the solderability of ENIG is reflected from Ni layer, so the au layer shall not be too thick. Or else there will be frangibility and solder pot unstable issue. Au is to protect the Ni layer and prevent from Ni oxidation and dialysis. So it shall not be too thin.现在的Ni/Au生产线都采用Atotech公司的Atotech化学Ni/Au工艺。

Nowadays most Ni/Au production lines are adopting atotech chemical Ni/Au technology developed by Atotech company.沉镍Electroless Nickel1 沉镍原理概述Electroless Nickel Principle introduction沉镍金工艺的沉镍的原理，实际上反而从“化镍浸金”一词中能够较容易地被我们所理解。

即其中镍层的生成是自催化型的氧化-还原反应，在镀层的形成过程中，无需外加电流，只靠高（85-1000C左右）槽液中次磷酸钠（NaH2PO2）还原剂的作用，即可在已活化的铜表面反应析出镍镀层。

而沉镍金工艺中金镀层的生成，则是典型的置换反应。

当PCB板进入金槽时，由于镍的活性较金大，因而发生置换反应，镍镀层表面逐渐被金所覆盖。

·The Principle of Electroless Nickel can be more easily understood from the word of “Electroless Nicke Immersion Gold”. That means the nickel layer is generated from the Autocatalytic redox reaction. During the coating forming process, impressedcurrent is not needed. Under NaH2PO2 reductant in bath with high temperaturebetween 85-1000C, nickel layer can be formed via activated copper surface reaction.But the gold layer is generated via typical replacement reaction. When PCB enters the gold bath, as the nickel is more active than gold, there will be replacement reaction.So the nickel layer will be covered by gold.使用次磷酸盐的化学镀镍只能覆盖某些金属：镍、铁、钴、钯、铱和铝等。

在铜和黄铜以及其它金属上镀镍时，必须使它们同比镍更活泼的金属或钯接触。

化学镀镍层是含磷在15%以下的Ni-P合金。

化学镍金的配方有碱性和酸性两种类型，在PCB领域中以酸性配方为主。

Electroless Nickel by hypophosphite is only applicable for Ni, Fe, Co, Pd, Ir and Al. To electroless Ni on copper and yellow metal, they shall react with the metal which is more active than nickel. Electroless Ni layer is alloy with less than 15% phosphorus. There are alkalinity and acidity electroless Ni, while acidity is more popular in PCB field.以下简单介绍一个沉镍的反应过程：Below is the brief introduction of electroless Ni reaction:关于沉镍的反应机理其过程基本上用一个反应式即可表达：The reaction mechanism of electroless Ni can be expressed by one equation:催化剂Catalyst2H2PO2+Ni2++2H2O → 2H2PO3+H2↑+2H++Ni但实际中，在镍槽中发生的化学反应，至少包含以下：But in actual, the chemical reaction in Ni bath shall at least include two of below:(1)H2PO2+H2O→HPO32-+H-+2[H]催化剂Catalyst(2)Ni2++2[H] → Ni+2H+催化剂Catalyst(3)H2PO2+[H] → H2O+OH+P(4)H2PO2+H2O→H2PO3+H2↑上述反应说明如下：Explanation for above reaction as below:（1）部分次磷酸根在催化剂的作用下水解并氧化成磷酸根，同时放出二个氢原子并且被吸附在催化剂表面。

Part of sodium Phosphate radical can be hydrolyzed and oxidized tophosphate radical with catalyst. Meanwhile, it will release twohydrogen(H) atom, which is absorbed on the catalyst surface.（2）Ni2+在催化剂表面被H原子迅速还原成镍原子Ni2+ will be quickly reduced to Ni atom via H atom on the catalystsurface.（3）少数H2PO2-在催化剂的作用下还原，产生磷原子并与镍形成化合物Few H2PO2 will be reduced with catalyst and generate P atom andform chemical compound with Ni.（4）部分H2PO2-在催化剂的作用下氧化，产生氢气自镍层表面向溶液上方逸出，此氢气也可钏进镍的沉积。

Part of H2PO2 will be oxidized with catalyst and generate hydrogenwhich flee from the Ni surface to the place above the solution. Thehydrogen can also accelerate the deposit of Ni.决定镍还原反应速度的是，次磷酸盐分解形成氢原子的反应。

升高温度和增加次磷酸盐的浓度，以及添加某些有机酸时，次磷酸盐的分解加快。

What decide the Ni reduction speed is the reaction of hypophosphite reduced to H atom. Rising the temperature, increasing the concentration of sodium phosphate and adding some organic acid can speed up the reduction of sodium phosphate.2 各种因素对镀镍速度的影响All factors affected electroless Ni speed（1）温度Temperature酸性化学镀镍的过程只能在高温度（900C左右）下进行。

温度从900C升高到1000C，镍的沉积速度增加一倍。

Acid electroless Ni procedure can only be done under high temperature (at about 900C ). If increasing temperature from 900C to 1000C, Ni deposit speed will be double.（2）PH值PH ValuePH值的最佳值是5或稍高，此时过程的速度为10-30um/h。

当PH值降低时，在酸性溶液中的镀镍速度减慢，直到过程完全停止。

The best PH value is 5 or higher. And the speed in this condition will be10-30um/h. When PH decrease, electroless Ni speed in acid solution will slow down until completely stop.（3）镍盐的浓度Concentration of Ni salt当次磷酸盐浓度较低时，镍盐浓度的变化对镍沉积速度影响不大。

然而，如果在增加镍盐浓度的同时增加次磷酸盐含量，则过程的速度加快。

因此，镀镍速度依赖于溶液中镍盐和次磷酸盐的摩尔比例。

最合宜的摩尔比值通常为0.4，范围在0.25-0.6之间。

When the concentration of hypophosphite is lower, the change of Ni salt concentration will seldom affect the Ni deposit speed. However, if adding concentration of odium phosphate and Ni salt concentration at the same time, the speed will be faster. Therefore, electroless Ni speed depends on the Molar ratio between Ni salt and odium phosphate in the solution. The best Molar ratio is generally 0.4. And the scope is between 0.25-0.6.（4）添加剂Additive对沉积极速度影响颇大的是有机添加剂：乙酸醇、醋酸、甲酸以及这些酸的盐类。