- \n
- What\u2019s Immersion Silver? <\/a>\n\n<\/li>\n
- Immersion silver vs. immersion gold (ENIG\uff09<\/a>\n\n<\/li>\n
- Common Problems and Solutions During Immersion Silver<\/a>\n\n\n
- \nSolderability (IC Hole)<\/a>\n\n<\/li>\n<\/ul>\n
- Why Choose Immersion Silver for Your Flex-rigid PCB?<\/a>\n\n<\/li>\n
- Disadvantages of Immersion Silver<\/a>\n\n<\/li>\n
- Handling and Storage of Immersion Silver Flex-rigid PCB<\/a>\n\n<\/li>\n
- FAQ<\/a>\n\n\n
- \nImmersion silver vs. silver plating<\/a>\n\n<\/li>\n
- What materials are in rigid flex PCB?<\/a>\n\n<\/li>\n<\/ul>\n
- Conclusion<\/a>\n<\/li><\/ul>\n\n
What\u2019s Immersion Silver? <\/h2>\n\n\n
![\"Components](\"https:\/\/flexipcb.com\/wp-content\/uploads\/2023\/03\/1-12.jpg\")
<\/figure>\n\n\n\n(Components on a PCB)<\/p>\n\n\n\n
An immersion silver treatment involves depositing a thin silver layer on the circuit board\u2019s copper surface. <\/p>\n\n\n\n
This treatment aims to guard the exposed copper pads against deterioration and oxidation. <\/p>\n\n\n\n
Surprisingly, this process\u2019s awareness relied on the potential difference between copper and silver to let them pass through some displacement reaction.\u00a0<\/p>\n\n\n\n
Generally, the immersion silver treatment process is straightforward, easy, and consumes less time. <\/p>\n\n\n\n
Moreover, you should add some organic matter to the treatment process to eliminate electromigration. <\/p>\n\n\n\n
However, the quantity of this organic matter is mostly below 1%. Furthermore, flex-rigid circuit board<\/a> fabrication and manufacturers employ immersion silver for aluminum wire bonding and EMI shielding. <\/p>\n\n\n\n
In most cases, immersion silver has an average surface layer of 5 to 18 microinches. Also, they can last for as long as one year if you handle them properly.<\/p>\n\n\n
Immersion silver vs. immersion gold (ENIG\uff09<\/h2>\n\n\n
![\"A](\"https:\/\/flexipcb.com\/wp-content\/uploads\/2023\/03\/2-11.jpg\")
<\/figure>\n\n\n\n(A flexible PCB on the surface)<\/p>\n\n\n\n
As we highlighted, immersion silver<\/a> involves immersing the copper circuit board in silver ions. This is the best option for PCBs with EMI shielding and comes in handy for wire bonding and dome contacts. <\/p>\n\n\n\n
Generally, the silver, in this case, has a 5 to 18 microinches thickness.\u00a0<\/p>\n\n\n\n
Surprisingly, silver immersion is environmentally better than immersion gold. Additionally, it comes at a lesser cost. <\/p>\n\n\n\n
On the other hand, we have immersion gold, otherwise known as ENIG<\/a>. <\/p>\n\n\n\n
This option has two layers of metallic coating consisting of 2 to 8 microinches of gold over 120-240 microinches of nickel, which acts as a barrier to the copper surface. Also, gold offers low contact resistance and protects nickel during storage.\u00a0<\/p>\n\n\n\n
Thanks to the implementation of the RoHS<\/a> regulation, gold is now the most popular finish for circuit boards. Moreover, it\u2019s more durable than immersion silver. <\/p>\n\n\n\n
However, you’ll find it more expensive than immersion silver.<\/p>\n\n\n
Common Problems and Solutions During Immersion Silver<\/h2>\n\n\n
There are common problems you\u2019ll encounter during immersion silver, and we\u2019ll discuss them below:<\/p>\n\n\n\n
Normally, copper acts as both the cathode and anode. <\/p>\n\n\n\n
Therefore, the reduction of silver ions and oxidation of copper happens simultaneously. Consequently, a silver-plated layer forms on the copper surface.\u00a0<\/p>\n\n\n\n
However, any gap between the copper circuit and solder mask limits the silver ions supply in the gap. <\/p>\n\n\n\n
This way, copper becomes a sacrificial anode, thus offering the electrons for the silver ions reduction reaction.\u00a0<\/p>\n\n\n\n
Surprisingly, you can reduce and eliminate the galvanic effects risks by doing the following:<\/p>\n\n\n\n
- \n
- Ensure the micro-etching is within the required amount<\/li>\n\n\n\n
- Never connect small copper lines and large copper surfaces in the circuit board design<\/li>\n\n\n\n
- Use a less corrosive immersion silver process having the right pH. Also, avoid increasing the silver thickness. <\/li>\n\n\n\n
- Employ a chemical-resistant solder mask and optimize imaging, curing, pretreatment, and developing processes to improve the bond between the copper surface and solder mask.<\/li>\n<\/ul>\n\n\n
Solderability (IC Hole)<\/h3>\n\n\n
You might encounter IC hole solderability challenges thanks to hole wall quality. In most cases, the copper thickness is insufficient, or the hole is thick. <\/p>\n\n\n\n
Ensure the silver position is 100% copper to get the best immersion layer. <\/p>\n\n\n\n
Also, during storage, ensure the PCBs are under a humidity and temperature of 40% and 30\u00b0C, respectively. And when you decide to use the circuit board, the one in-store should come out first.\u00a0<\/p>\n\n\n
Why Choose Immersion Silver for Your Flex-rigid PCB?<\/h2>\n\n\n
![\"A](\"https:\/\/flexipcb.com\/wp-content\/uploads\/2023\/03\/3-10.jpg\")
<\/figure>\n\n\n\n(A flex PCB)<\/p>\n\n\n\n
Immersion silver is increasingly used to develop flex-rigid circuit boards. Check out some of the features below: <\/p>\n\n\n\n
- \n
- One of the main functions of immersion silver is to allow the solder to spread evenly on the board. Therefore, it becomes easier to solder components. <\/li>\n\n\n\n
- Designers can assemble fine components like pitch and BGA on the PCB with immersion silvers.\u00a0<\/li>\n\n\n\n
- Surprisingly, it\u2019s environment-friendly thanks to RoHS-compliant technology and has no hazardous substances.\u00a0<\/li>\n\n\n\n
- With immersion, silver designers are able to implement multiple soldering reflows<\/a>.\u00a0<\/li>\n\n\n\n
- Immersion silver is a superior technology with excellent electrical properties. Moreover, it has a flat surface and a low contact resistance. <\/li>\n\n\n\n
- Immersion silver offers better conductivity. Therefore, you can comfortably use it where you need a high-frequency signal design. <\/li>\n\n\n\n
- You\u2019ll find immersion silver to be cost-effective, thus eliminating any cases of budget constraint.\u00a0<\/li>\n<\/ul>\n\n\n
Disadvantages of Immersion Silver<\/h2>\n\n\n
- \n
- You should solder components on the same day you remove the circuit board from storage.<\/li>\n\n\n\n
- It\u2019s less durable than immersion gold, thanks to a lack of a nickel layer underneath.<\/li>\n\n\n\n
- If you handle it inappropriately, you can easily tarnish it. <\/li>\n<\/ul>\n\n\n
Handling and Storage of Immersion Silver Flex-rigid PCB<\/h2>\n\n\n
![\"An](\"https:\/\/flexipcb.com\/wp-content\/uploads\/2023\/03\/4-10.jpg\")
<\/figure>\n\n\n\n(An engineer handling a PCB)<\/p>\n\n\n\n
While handling immersion silver, we recommend using gloves to avoid contamination. Anything, including sweat, that drops on the circuit board can react with the silver and damage the board.\u00a0<\/p>\n\n\n\n
Moreover, you should solder the circuit board within one day after removing them from storage. <\/p>\n\n\n\n
You\u2019ll know immersion silver PCBs are contaminated if they showcase black or yellow discoloration. Always keep in touch with a circuit board technician or expert any time you notice contamination.\u00a0<\/p>\n\n\n\n
If you have stored your circuit board for a long time, you should conduct a solderability test before assembly. <\/p>\n\n\n\n
This will require reflow and solder paste, and if you notice a complete wetting, the test board is alright. However, we have a solder paste<\/a> specific to immersion silver surfaces.\u00a0<\/p>\n\n\n\n
Finally, use only water to wash or clean immersion silver finishes. Also, store the surface boards in sealed containers to eliminate contamination. <\/p>\n\n\n
FAQ<\/h2>\n\n
Immersion silver vs. silver plating<\/h3>\n\n\n
Immersion silver involves depositing a thin layer on your circuit board\u2019s surface. We restrict this process purely to circuit boards. However, silver plating involves covering a jewelry base metal like brass or copper using a thin layer. <\/p>\n\n\n\n
This could happen on a jewelry metal material with a thickness of 1-10 microinches.\u00a0<\/p>\n\n\n\n
How thick is immersion silver PCB?<\/p>\n\n\n\n
Generally, immersion silver has a thickness of 5 to 18 microinches. Moreover, it comes with a shelf life of about 12 months. <\/p>\n\n\n
What materials are in rigid flex PCB?<\/h3>\n\n\n
All rigid-flex circuit boards have a substrate material, mostly polyester or polyimide. Also, we have a copper conductor material.<\/p>\n\n\n\n
Sometimes, we add a thin zinc layer to improve copper longevity. Finally, adhesives create a secure connection between the copper and the substrate.\u00a0<\/p>\n\n\n
Conclusion<\/h2>\n\n\n
As we\u2019ve seen, immersion silver involves depositing a thin silver layer to protect the copper surface on your rigid-flex circuit board<\/a>. <\/p>\n\n\n\n
Consequently, your copper surface will experience less deterioration and oxidation. Surprisingly, the process is straightforward, easy, and consumes less time. <\/p>\n\n\n\n
While implementing the immersion silver process, we recommend adding some organic matter to the treatment process to eliminate electromigration.\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"
Over the past few years, we have had a rise in the design and manufacturing of immersion silver flex-rigid PCB. You might not know immersion silver is an environment-friendly finish on the circuit board\u2019s copper surface that guarantees good component soldering.\u00a0 Surprisingly, the process involves depositing a thin silver layer by undergoing a chemical reaction … <\/p>\n
- What materials are in rigid flex PCB?<\/a>\n\n<\/li>\n<\/ul>\n
- Why Choose Immersion Silver for Your Flex-rigid PCB?<\/a>\n\n<\/li>\n
- Immersion silver vs. immersion gold (ENIG\uff09<\/a>\n\n<\/li>\n