PCB表面处理又称为PCB表面处理,是一种通过化学或物理方法在印刷电路板的铜垫上涂上一层金属或化合物的技术。PCB表面处理有两个主要作用。第一,避免铜垫/导体氧化;第二,使PCB易于在其上焊接电子元件。
我们可以进行如下几乎所有类型的表面处理。
浸金是 ENIG 的简称,全称是化学镀镍浸金,即在铜表面覆盖一层厚厚的镍和金,无需阻焊,以保护 PCB 在正常大气中免受氧化。它具有非常长的保质期(12 个月),并且可以实现非常好的电气性能,因为金具有出色的导电性。由于它可以应用于非常高密度的 PCB,因此浸金在更高标准的 PCB 中非常受欢迎。
通过化学置换反应,在PCB的铜焊盘上会沉积一层银。由于银具有非常好的导电性,因此沉银可以提供非常好的电气性能。同时,在PCB组装过程中,银也易于与锡焊接。沉银的成本比沉金便宜,但缺点是在正常环境下暴露时更容易发黄。
浸锡工艺是通过化学置换反应在印刷电路板的铜焊盘上沉积一层锡,锡一来可以保护铜不被氧化,二来对电路板上的元器件焊接性很好,由于表面处理和焊膏/焊条都是锡,所以可焊性很好,相比HAL,浸锡工艺很光滑,但成本较高。
ENEPIG全称是Electroless Nickel Electroless Palladium Immersion Gold,是在ENIG基础上发展起来的,区别于传统的沉镍/金(ENIG)表面处理工艺,在镍层和金层之间引入了一层钯,可以有效防止镍向金层迁移而导致PCB组装过程中出现缺陷,具有良好的布线性能和耐老化性能,同时还可以避免ENIG工艺中出现的黑焊盘缺陷。
HAL 即热风整平。在此过程中,锡会被熔化,然后用热风吹平 (吹) 在 PCB 表面上。然后焊料会粘附在没有阻焊层的铜垫上,其厚度约为 5-40um。HAL 是最常用的表面处理,因为它具有优异的可比性和节省成本。
用化学方法在未涂阻焊层的铜线上放置一层有机化合物。这层薄薄的有机膜/化合物可以保护铜线在正常环境下不被氧化。同时,OSP表面非常适合PCB焊接,因为在SMT焊接或波峰焊过程中,有机膜会因为高温而被蒸发。
镀金工艺是在没有被阻焊层覆盖的铜线上先镀一层镍,然后再镀上一层厚度约为2-5u''的金。镀镍是为了防止金和铜之间的扩散导致PCB组装过程中出现缺陷,镀金是为了防止氧化,同时保证良好的可焊性。硬金是指由于含有钴和其他元素,表面较硬,看起来比软金更亮。硬金主要用于非焊接部位,最典型的是边缘连接器。
镀金工艺是在没有被阻焊层覆盖的铜线上先镀一层镍,然后再镀上一层厚度在5-30u''左右的金。镀镍主要是为了防止金和铜之间的扩散,镀金是为了防止氧化和PCB上的元器件焊接。软金镀层采用的是纯金(不含其他化合物),金面看起来没有硬金镀层那么光亮。软金主要用于印刷电路板铜焊盘上电子元器件的焊接。
为了充分利用不同表面处理的优势,可以在一块印刷电路板上选择两种或两种以上的表面处理方法,以达到最佳性能。常见的表面处理有:ENIG+OPS、ENIG+边缘连接器镀硬金、HAL+镀硬金、OSP+镀硬金。
Surface Treatment | cost | quality guarantee period | solderability | Advantages and disadvantages |
---|---|---|---|---|
HAL containing lead | normal | 12 months | tall | High cost-effectiveness and high production efficiency. Very good weldability. Not compliant with RoHS/REACH standards. Not applicable when the distance between the soldering pins is less than 0.5mm. Not suitable for BGA because it is not smooth enough. |
No PB HAL | normal | 12 months | tall | High cost-effectiveness and high production efficiency. Very good weldability. Not suitable for welding needles with a distance less than 0.5mm. Not suitable for BGA because it is not smooth enough. |
OSP | low | 6 months | normal | High cost-effectiveness and high production efficiency. Not suitable for mixed assembly of PTH and SMT. Poor thermal stability. After the first reflow soldering, the PCB should usually be soldered within 14 hours. Not suitable for PCBs with EMI grounding areas, mounting holes, and test pads. It is also not suitable for crimping holes. |
Gold plating | tall | 12 months | tall | Good weldability, excellent conductivity, long shelf life, very durable and stable. The surface is very smooth and suitable for fine spacing. The optimal solution for edge connectors requires multiple insertions and removals, which is very costly. There is a risk of embrittlement in welding points/seams. |
Immersion Gold | tall | 12 months | tall | Good weldability, excellent conductivity, long shelf life, very durable and stable. The surface is very smooth and suitable for fine spacing. There is a risk of 'black solder pad' issues. |
immersion silver | normal | 6 months | tall | Excellent weldability and high cost-effectiveness. The surface is very smooth, suitable for small ICs. Easy to sulfurize (sensitive to sulfur), non welding areas are prone to discoloration at high temperatures. |
Immersion Tin | normal | 6 months | tall | Excellent solderability, high cost-effectiveness, very smooth surface, suitable for small integrated circuits, high requirements for tin dipping chemicals |
England Pig | tall | 12 months | tall | There is no risk of 'black pad', and the surface treatment is very durable and stable. It is a perfect alternative to OSP or ENIG. But the cost is relatively high. |
Surface Treatment | Storage conditions and shelf life (from production date) | Storage conditions and workshop lifespan after unpacking | ||
---|---|---|---|---|
Storage situation | quality guarantee period | Storage situation | Workshop Life | |
immersion silver | Temperature ≤ 27 ℃, humidity ≤ 60%, no acid, alkali or organic solution | 6 months | Temperature ≤ 27 ℃, humidity ≤ 60%, no acid, alkali or organic solution | ≤ 48 hours |
(OSP) Organic Solderability Protective Agent | Temperature ≤ 27 ℃, humidity ≤ 60%, no acid, alkali or organic solution | 6 months | Temperature ≤ 27 ℃, humidity ≤ 60%, no acid, alkali or organic solution | ≤ 24 hours |
ENIG,ENEPIG, gold-plating | Temperature ≤ 27 ℃, humidity ≤ 60%, no acid, alkali or organic solution | 12 months | Temperature ≤ 27 ℃, humidity ≤ 60%, no acid, alkali or organic solution | ≤ 24 hours |
Tin immersion | Temperature ≤ 27 ℃, humidity ≤ 60%, no acid, alkali or organic solution | 6 months | Temperature ≤ 27 ℃, humidity ≤ 60%, no acid, alkali or organic solution | ≤ 24 hours |
(HASL) Hot air soldering and leveling machine | Temperature ≤ 27 ℃, humidity ≤ 60%, no acid, alkali or organic solution | 12 months | Temperature ≤ 27 ℃, humidity ≤ 60%, no acid, alkali or organic solution | ≤ 24 hours |
Attention: For HDI boards, if the storage time exceeds three months but is less than six months, the PCB needs to be baked before production and assembled within 8 hours
Silver immersed PCB baking temperature 120 ± 5 ℃, 2 hours, stacking height ≤ 2.5cm;
Whole board nickel gold PCB baking temperature: 120 ± 5 ℃, 2-4 hours, stacking height ≤ 2.5cm;
The baking temperature for OSP surface treatment and selective OSP surface treatment PCB is 120 ± 5 ℃, 2 hours, and the stacking height is ≤ 2.5cm.
The oven must be kept clean and free of volatile gases such as corrosive chemicals such as acids, alkalis, and organic solvents.
If pursuing cost-effective FPC manufacturing services, choosing a Chinese manufacturer is the best choice. As a manufacturing powerhouse, China has abundant resources, cheap labor, and a large number of technical personnel. We recommend Haibo, a Chinese FPC assembly service provider with over 10 years of experience, who has performed outstandingly in various aspects
Efficient and reasonable quotation:There is an efficient quotation process to assist you in making decisions, providing reasonable prices and highly competitive quotes in China.
High quality and reliable products:Produce high standard printed circuit boards, manufacture and test according to specifications, international standards, and internal controls, and conduct pre production inspections to ensure robust processes.
Quick and on-time delivery:The assembly equipment is in good condition, with high productivity, minimal downtime, short delivery time, and also provides urgent services.
Timely and effective response:Always respond to customer needs, provide accurate information, answer questions through multiple channels, and offer one-stop services.
Strong technical strength:China's FPC manufacturing technology is leading, and Haibo has a complete SMT solution that covers assembly, inspection, and other capabilities. It also provides prototype production and customization services.
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Contact: Chen Changhai
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E-mall: haibo_fpcba1668@163.com
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