🔊 A Must-Know for SMT Solder Paste! The Core Logic of Refrigeration + Rewarming—Every Step Is Indispensable

发布于： 2013-06-20 11:42

Core Insights: SMT Solder Paste Management Starts with Refrigeration & Rewarming

In SMT assembly production, solder paste is the core material for soldering, and its condition directly determines soldering yield. Many manufacturers neglect the standard procedures for solder paste refrigeration and rewarming, resulting in deteriorated solder paste, reduced activity, and subsequent mass defects such as cold joints and solder bridges. With many years of SMT manufacturing experience, Tenpoint fully explains the core logic of solder paste refrigeration and rewarming to help you avoid quality risks!

1. Why Must Solder Paste Be Refrigerated? The Core Is to "Prevent Deterioration"

Solder paste is a mixture of solder powder and flux, both of which are temperature-sensitive and prone to deterioration at room temperature. Therefore, strict refrigeration control is essential:

Refrigeration Standard: Solder paste must be stored at a strictly controlled temperature of 0–10°C. Freezing and temperature overruns are strictly prohibited to avoid damaging solder paste performance.
Purpose of Refrigeration: A low-temperature environment of 0–10°C effectively slows down the volatilization of flux, prevents oxidation of solder powder, avoids solder paste deterioration, and maintains stable original performance, laying a solid foundation for subsequent soldering quality.

Friendly Reminder: If solder paste is not refrigerated properly, flux will volatilize easily and solder powder will oxidize, causing the paste to thicken and lose fluidity. This leads to frequent soldering issues such as cold joints, solder bridges, and poor wetting, directly affecting product quality and causing unnecessary losses.

2. Core Role of Solder Paste Rewarming: Restore Activity for Smooth Soldering

Refrigerated solder paste cannot be used directly; rewarming is an indispensable key step whose core function is to "restore solder paste activity":

Rewarming Standard: After removing solder paste from the refrigerator, it must stand sealed at room temperature for 4 hours. Opening the package in advance is strictly forbidden.
Purpose of Rewarming: Refrigerated solder paste is dry and low in activity. Rewarming gradually restores its activity, improves fluidity and wettability, ensures smooth printing and soldering, and prevents defects like uneven printing and cold joints caused by poor fluidity.

3. Critical Supplement: Must Stir Evenly After Rewarming

Many industry practitioners overlook a key detail: during refrigeration, solder powder and flux separate due to density differences and will not recombine automatically even after rewarming.

Therefore, after rewarming and before opening for use, solder paste must be fully stirred to ensure uniform mixing of solder powder and flux. This achieves optimal soldering performance, avoids defects caused by uneven mixing, and further improves soldering yield.

Tenpoint: Strict Solder Paste Control Guarantees Soldering Yield from the Source

Higher soldering yield starts with detailed control. With years of expertise in SMT manufacturing, Tenpoint strictly implements full-process standards for solder paste refrigeration, rewarming, and stirring, with dedicated personnel monitoring temperature and recording time to eliminate issues such as solder paste deterioration and insufficient activity at the source.

Equipped with advanced inspection equipment including 3D SPI, pre-reflow and post-reflow AOI, we conduct strict full-process testing from solder paste application to soldering completion, ensuring soldering quality for every PCB. With professional capabilities, we deliver stable and reliable products to our customers.