1. The PCB must implement protective measures on the copper surface to be soldered to ensure solderability. However, for high-density PCBs, traditional spray tin processing often fails to meet the surface treatment requirements for high-density assemblies.

2. The industry introduced the so-called Entek process many years ago. At that time, the formulation and industrial environment requirements were not mature, resulting in a very short weather resistance period, ranging from a few hours to two or three days.

3. Consequently, its application was mainly limited to direct production and use in certain factories, making it an unsuitable option for some specialized PCB manufacturers.

4. Nevertheless, due to improvements in subsequent formulations, the trend towards lead-free assembly, cost advantages, and the high-density structure of products, the development of organic solder masks has made notable progress.

5. The organic solder mask formulations commonly available on the market are mainly based on organic compounds such as BTA, AI, ABI, etc. Since these organic substances have various molecular structures, manufacturers often classify their chemical properties as proprietary, limiting users’ ability to fully understand and assess their effects on PCB production.

6. The general organic solder mask has a thickness of about 0.4 µm to facilitate multiple fusion welding. While it is inexpensive and straightforward to use, it still presents the following drawbacks:

7. 1. OSP is transparent, making it difficult to measure and inspect visually.

8. 2. Excessive film thickness can hinder the use of low-solid content and low-activity no-clean solder paste, and CU5SN6 IMC, which is beneficial for bonding, is not easily formed.

9. 3. Multiple assembly operations often require a nitrogen-rich environment.

10. 4. If partial gold plating is followed by OSP, copper from the operating bath may deposit on the gold, potentially causing issues with some products.

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1. The most well-known product in this category is the copper protection agent sold by ENTHON, which is available in both methanol and aqueous solutions. The product, coded CU-XX, has various names depending on its application. BTA is a white to light yellow, odorless, crystalline powder. It is highly stable in both acidic and alkaline conditions and resists oxidation-reduction reactions. It forms stable compounds with metals, creating a protective film on the copper surface to prevent rapid oxidation and maintain solderability.

2. These organic compounds share the common feature of forming appropriate complexes with copper, preventing oxidation and preserving soldering properties. Currently, there are three primary product systems: acetic acid, formic acid, and rosin. The rosin system, which requires cleaning after assembly, is less commonly used due to its challenging cleanup process. Most users prefer the liquid systems, which enhance growth rates but can be difficult to control due to the rapid evaporation of water. An increase in pH often causes IMIDAZOLE to become insoluble and crystallize, necessitating pH adjustments to ensure optimal performance.