The technology and application of lead-free low-temperature solder paste have given birth to a new type of non cleaning solder paste

1、 Introduction

Low temperature solder paste, as a shining pearl in modern SMT production technology, leads the industry trend with its excellent feature of no cleaning. This solder paste carefully blends specially made solder paste with extremely pure spherical solder powder, ensuring unparalleled continuous printing clarity. With the high reliability of the low ion activator system, it presents minimal residue and amazing insulation resistance after reflow, even without cleaning, it can maintain extremely high reliability and stability.

2、 Product Highlights

Excellent printing performance: Whether it is precision solder pads as low as 0.3mm or T6 level fine operations, they can be easily handled, perfectly presenting the printing process.

Stable viscosity performance: In continuous printing, the viscosity change is minimal, and the service life of the steel mesh is outstanding. Even after 12 hours, it still maintains the same printing effect as before, neither dry nor hard.

Excellent form retention: Within a few hours after printing, the form remains firm and not afraid of collapse, ensuring precise and offset free surface mount components.

Excellent welding adaptability: It can demonstrate just the right amount of wettability in various welding areas, meeting the strict requirements of different grades of welding equipment, without the need for nitrogen environment, and performs excellently over a wide temperature range.

Environmentally friendly welding residue: After welding, the residue is rare and has a light color, high insulation impedance, and treats PCBs gently, truly realizing the dream of no cleaning.

Accurate ICT testing: Excellent testing performance, avoiding misjudgment, and safeguarding quality.

The nemesis of BGA soldering difficulties: a formula designed specifically for BGA products to easily tackle soldering challenges.

The right-hand man of through-hole technology: the best choice in through-hole roller coating technology.

3、 Technical essence

Strict quality inspection: Following authoritative standards such as ANSI/J-STD-004/005/006, JIS Z 3197-86, JIS/Z3283-86, and IPC-TM-650 to ensure excellent quality.

The secret of tin powder alloy: The alloy composition strictly follows the J-STD-006 standard. For specific composition, please refer to the tin powder quality certificate.

4、 Application Guide

The way of selection: Carefully select the alloy composition, tin powder size, and metal content according to the customer's product and process requirements. For lead-free soldering systems, Sn42Bi58 alloy paired with T3 tin powder is an ideal choice, while finer tin powder can be selected for fine pitch applications.

Prelude for use:

Warm up art: Solder paste needs to be refrigerated at 5-10 ℃ and naturally warmed up for 4 hours before use to avoid the risk of "tin explosion" caused by water vapor condensation.

Mixing secret: After warming up, mix thoroughly to ensure even distribution of flux and tin powder. Both manual and machine mixing are acceptable, and the time needs to be accurately controlled.

Printing art: The printing process is crucial, and high-quality steel mesh and equipment are the cornerstone of perfect printing. Pay attention to adjusting the printing conditions to ensure that the scraper and steel mesh are clean and dust-free, the PCB is firmly fixed, the printing volume is moderate, and fresh solder paste is added in a timely manner.

Wisdom of reflow soldering: Following the recommended reflow temperature curve, precise control of preheating, immersion, reflow, and cooling zones ensures excellent quality of solder joints.

Follow up processing: Although the residue is small, it can still be cleaned according to the needs. When carrying out repair work, it is recommended to use compatible tin wires and soldering flux.

5、 Packaging and Transportation

Each bottle is 500g, packed with wide mouth PE bottles, sealed with inner covers, and packed in foam boxes, with a maximum of 20 bottles per box. The temperature in the box shall not exceed 35 ℃ during transportation.

6、 Storage and shelf life

After receiving the solder paste, please store it in the refrigerator immediately. The recommended temperature is 5 ℃~10 ℃. Both excessively high and low temperatures can affect its performance. Under normal storage conditions, the shelf life is 6 months. Please ensure sufficient warming before use.

7、 Health and Safety

Although solder paste is a chemical product, please use it with confidence. Be sure to follow the MSDS guidance, take protective measures, and avoid prolonged exposure to smell, food, skin, and eye contact. The homework site should maintain good ventilation and smoking and eating are strictly prohibited. Solder paste is flammable, please stay away from sources of fire. Please dispose of discarded solder paste according to regulations.

Reflow Temperature Curve (Sn42Bi58)

Please refer to the attached curve chart to set the reflow oven temperature to ensure excellent welding quality. Accurate control of the preheating zone, immersion zone, reflow zone, and cooling zone reduces solder paste sagging and tin ball phenomenon, suitable for the vast majority of products and process conditions.

Accurate control of temperature curve is crucial for ensuring welding quality during SMT reflow process. The following is a detailed analysis and operational suggestion for each stage of the reflow temperature curve you provided:

‌A.  Preheating zone (25-33% of heating channel)

The main purpose of this stage is to gradually evaporate the volatile solvents in the solder paste and reduce the thermal shock to the components. The heating rate should be controlled between 1.0~3.0 ℃/s to avoid solder paste flow, component deterioration, and component damage caused by rapid heating. Operators should closely monitor the temperature feedback of the heating equipment to ensure a smooth heating process.

‌B.  Immersion zone (33-50% of heating channel)

At this stage, the flux becomes active and undergoes chemical cleaning to ensure uniform temperature in all parts of the PCB before reaching the reflow zone. The temperature should be maintained between 110-130 ℃, and the time should be controlled between 90-150 seconds. The heating rate should be less than 2 ℃/second. The key to this stage is to ensure that the flux is fully utilized, laying a solid foundation for the subsequent soldering process.

‌C.  Return welding area

This stage is the core of the welding process, where the metal particles in the solder paste melt and form solder joints. The maximum temperature should be controlled between 175-180 ℃ and maintained for 50-80 seconds. If the peak temperature is too high or the reflow time is too long, it may cause the solder joint to darken, the flux residue to carbonize and discolor, and the components to be damaged; On the contrary, if the temperature is too low or the time is insufficient, it may affect the wettability of the solder, resulting in poor solder joint quality and even virtual soldering. Therefore, operators need to accurately set and monitor the temperature and time of the reflow zone based on specific product characteristics and process requirements.

‌D.  Cooling zone

After leaving the reflow zone, the substrate enters the cooling zone. At this stage, it is necessary to control the cooling rate of the solder joints to optimize their strength. The cooling rate should be less than 4 ℃, and the cooling termination temperature should ideally not exceed 75 ℃. Excessive cooling rate may cause components to withstand excessive thermal stress and be damaged; A too slow cooling rate may form larger grain structures, affecting the strength of solder joints and the stability of components. Therefore, appropriate cooling methods and rates should be adopted in the cooling zone to ensure the quality of the solder joints.

In summary, precise control of the reflow temperature curve of Suzhou Nofel is crucial for the SMT soldering process. Operators need to strictly follow the temperature and time requirements of each stage based on product characteristics and process requirements, and closely monitor temperature changes during heating and cooling processes to ensure stable and reliable welding quality.