Matters needing attention:

Sulfur-free paper is a special paper for PCB surface treatment process, which is stored in a cool and ventilated warehouse, stacked smoothly, away from direct sunlight, away from fire sources and water sources, and protected from high temperature, moisture and contact with liquids (especially acid and alkali)!  

specifications

Weight: 60g, 70g, 80g, 120g.
Orthogonality value: 787*1092mm.
Generous value: 898*1194mm.
Can be cut according to customer requirements.

Storage conditions and shelf life.

Store in a dry and clean warehouse at 18℃ ~ 25℃, away from fire sources and water sources, avoid direct sunlight, and seal the package with a shelf life of one year.

Technical parameters of products.

1. sulfur dioxide ≤50ppm.
2. Adhesive tape test: the surface has no hair falling phenomenon.

Application

Mainly used in silver-plated packaging, such as circuit boards, LEDs, circuit boards, hardware terminals, food protection articles, glass packaging, hardware packaging, stainless steel plate separation, etc.

Why do you need sulfur-free paper?

Before we talk about why sulfur-free paper is used, we need to talk about the object “PCB” (printed circuit board) protected by sulfur-free paper-PCB is the support of electronic components and one of the important components in the electronic industry. Almost every kind of electronic equipment, from electronic watches and calculators to computers and communication equipment, needs PCB to realize the electrical interconnection between various components.

The main body of PCB is copper, and the copper layer easily reacts with oxygen in the air to generate dark brown cuprous oxide. In order to avoid oxidation, there is a process of silver deposition in PCB manufacturing, so PCB board is also called silver deposition board. Silver deposition process has become one of the final surface treatment methods of printed PCB.

Sulfur-free paper packaging circuit board, but even if silver deposition process is adopted, it is not completely without defects:

There is a great affinity between silver and sulfur. When silver encounters hydrogen sulfide gas or sulfur ions in the air, it is easy to produce a substance called silver sulfide (Ag2S), which will pollute the bonding pad and affect the subsequent welding process. Moreover, silver sulfide is extremely difficult to dissolve, which brings great difficulty in cleaning. Therefore, intelligent engineers have come up with a way to isolate PCB from sulfur ions in the air and reduce the contact between silver and sulfur. It is sulfur-free paper.

To sum up, it is not difficult to find that the purpose of using sulfur-free paper is as follows:

First, the sulfur-free paper itself does not contain sulfur and will not react with the silver deposition layer on the PCB surface. Using the sulfur-free paper to wrap the PCB can effectively reduce the contact between silver and sulfur.

Second, the sulfur-free paper can also play a role of isolation, avoiding the reaction between the copper layer under the silver deposition layer and the oxygen in the air.

In the link of choosing sulfur-free paper, there are actually tricks. For example, sulfur-free paper needs to meet ROHS requirements. High-quality sulfur-free paper not only does not contain sulfur, but also strictly removes toxic substances such as chlorine, lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyls, polybrominated diphenyl ethers, etc., which fully meets the requirements of EU standards.

In terms of temperature resistance, logistics paper has the special property of resisting high temperature (about 180 degrees Celsius), and the pH value of the paper is neutral, which can better protect PCB materials from oxidation and yellowing.

When packaging with sulfur-free paper, we should pay attention to a detail, that is, the PCB board with silver-immersed technology should be packaged immediately after it is produced, so as to reduce the contact time between the product and the air. In addition, when packaging the PCB board, sulfur-free gloves must be worn and must not touch the electroplated surface.

With the increasing requirement of lead-free PCB in Europe and America, the PCB with silver and tin deposition technology has become the mainstream of the market, and sulfur-free paper can fully guarantee the quality of silver or tin deposition PCB. As a kind of green industrial paper, sulfur-free paper will be more and more popular in the market, and become the packaging standard of PCB in the industry.

Reasons for using sulfur-free paper.

You must wear sulfur-free gloves when touching the silver-plated board. Silver plate must be separated from other objects by sulfur-free paper during inspection and handling. It takes 8 hours to finish the silver sinking board from the time of exiting the silver sinking line to the time of packaging. When packaging, the silver plating board must be separated from the packaging bag with sulfur-free paper.  

There is a great affinity between silver and sulfur. When silver encounters hydrogen sulfide gas or sulfur ions in the air, it is easy to form an extremely insoluble silver salt (Ag2S) (silver salt is the main component of argentite). This chemical change can occur in a very small amount. Because silver sulfide is gray-black, with the intensification of the reaction, silver sulfide increases and thickens, and the surface color of silver gradually changes from white to yellow to gray or black.

The difference between sulfur-free paper and ordinary paper.

Paper is often used in our daily life, especially every day when we were students. Paper is a thin sheet made of plant fiber, which is widely used. Paper used in different fields is different, such as industrial paper and household paper. Industrial paper such as printing paper, sulfur-free paper, oil-absorbing paper, wrapping paper, kraft paper, dust-proof paper, etc., and household paper such as books, napkins, newspapers, toilet paper, etc. So today, let’s explain the difference between industrial sulfur-free paper and common paper.

Sulfur-free paper

Sulfur-free paper is a special padding paper used in PCB silvering process in circuit board manufacturers to avoid chemical reaction between silver and sulfur in the air. Its function is to chemically deposit silver and avoid the chemical reaction between silver and sulfur in the air, resulting in yellowing. Without sulfur, it can avoid the disadvantages caused by the reaction between sulfur and silver.

At the same time, sulfur-free paper also avoids the chemical reaction between silver in the electroplated product and sulfur in the air, resulting in yellowing of the product. Therefore, when the product is finished, the product should be packaged with sulfur-free paper as soon as possible, and sulfur-free gloves should be worn when contacting the product, and the electroplated surface should not be contacted.

Characteristics of sulfur-free paper: sulfur-free paper is clean, dust-free and chip-free, meets ROHS requirements, and does not contain sulfur (S), chlorine (CL), lead (Pb), cadmium (Cd), mercury (Hg), hexavalent chromium (CrVI), polybrominated biphenyls and polybrominated diphenyl ethers. And can be better applied to PCB circuit board electronic industry and hardware electroplating industry.

The difference between sulfur-free paper and ordinary paper.

1. Sulfur-free paper can avoid the chemical reaction between silver in electroplated products and sulfur in air. Ordinary paper is not suitable for electroplating paper because of too many impurities.
2. Sulfur-free paper can effectively inhibit the chemical reaction between silver in pcb and sulfur in air when it is used in pcb industry.
3. Sulfur-free paper can prevent dust and chips, and impurities on the surface of electroplating industry will affect the electroplating effect, and impurities in pcb circuit may affect the connectivity.

Ordinary paper is mainly made of plant fibers, such as wood and grass. The raw materials of sulfur-free paper are not only plant fibers, but also non-plant fibers, such as synthetic fibers, carbon fibers and metal fibers, so as to eliminate sulfur, chlorine, lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyls and polybrominated diphenyl ethers from the paper. In order to make up for some shortcomings of the base paper, it is beneficial to improve the paper quality and achieve the purpose of optimizing the combination.