How and how to properly solder copper tubes of a refrigerator: solders, fluxes and secrets of the masters

When the refrigerator stops freezing or signs of freon leakage appear, the reason often lies in damage to the copper tubes - a key element of the refrigerant circulation system. Soldering these tubes requires not only skill, but also the right choice of materials: the wrong solder or flux can lead to repeated leaks, corrosion or even compressor failure. In this article, we will look at what solders and fluxes are suitable for different types of repairs, and how to avoid common mistakes. how professionals solder copper tubes of refrigerators, which solders and fluxes are suitable for different types of repairs, and how to avoid common mistakes.

The peculiarity of copper tubes in refrigerators is their thin walls (usually 0.6–1.2 mm) and work under pressure. This imposes stringent requirements on the strength of the seam and its resistance to vibration. For example, solder with a high tin content (for example, Sn97Cu3) will provide better fluidity, but may not withstand the pressure in the system, and silver-containing alloys (for example, Ag15) will give a strong seam, but will require a higher soldering temperature. In addition, flux residues inside the tube can clog the capillary system - therefore the choice acid or acid-free flux depends on the specific task.

If you are planning a DIY repair, it is important to consider the type of refrigerant. For example, for systems with R600a (isobutane) the tightness of the seam is critical, since this gas easily leaks through microcracks, and for R134a or R12 (in older models) less stringent requirements are acceptable. In the article you will find a comparative table of solders, step-by-step soldering instructions and answers to frequently asked questions - from choosing a torch to checking the seam for leaks.

1. Types of solders for soldering copper tubes of refrigerators

Solder is an alloy that melts at a lower temperature than copper and ensures the connection of parts. For refrigeration systems they use soft (low temperature) and hard (high temperature) solders, each of which has its own pros and cons. The choice depends on the diameter of the tube, the type of damage and the requirements for the strength of the seam.

The most common options:

• 🔹 Tin-lead solders (for example, POS-61 or POS-40): cheap and low-melting (180–250°C), but contain lead, which limits their use in modern refrigerators due to environmental standards. Suitable for old models with tubes with a thickness of 1 mm.
• 🔹 Lead-free solders (for example Sn97Cu3, Sn99Cu1): environmentally friendly, melts at 220–260°C, but require more thorough surface preparation. Used in modern refrigerators thin tubes.
• 🔹 Silver-containing solders (for example, Ag15, Ag45): provide high weld strength (up to 300 MPa), melt at 600–800°C. Used for critical areas (for example, connection to a compressor) or high-pressure tubes.
• 🔹 Phosphorus-copper solders (for example, CuP6): self-fluxing (do not require flux), melt at 700–800°C. Suitable for copper-copper connections, but incompatible with brass or steel.

For most household refrigerators, lead-free solders (for example, Sn97Cu3) or low-temperature silver-containing alloys (for example, Ag5). The latter are more expensive, but guarantee the reliability of the seam even with compressor vibrations. The use of lead solders in systems with R600a refrigerant can lead to a chemical reaction and clogging of the capillary tube - this is critical for inverter models LG, Samsung and Bosch recent years.

2. Fluxes: which one to choose and why it is important

Flux removes the oxide film from copper, improves solder wettability and prevents oxidation during soldering. In refrigeration systems flux residues inside the tube can cause corrosion or clogging of the capillary —therefore, its choice is no less important than solder. Fluxes are divided into three groups:

• 🔹 Acid fluxes (for example, FKSp, LTI-120): they actively remove oxides, but require thorough rinsing after soldering. Suitable for rough work (for example, repair of thick-walled tubes in old refrigerators).
• 🔹 Acid-free fluxes (for example, FIM, Boris): do not cause corrosion, but are less effective in case of strong oxidation. Used for thin-walled tubes (0.6–0.8 mm).
• 🔹 Fluxes-pastes (for example, Sanha Flux): convenient for spot soldering, do not spread, but can leave sticky marks. Popular with repairmen NoFrost-systems.

For soldering copper tubes of refrigerators borax-based acid-free flux is optimal (for example, FIM or Castolin 1901). It does not require flushing and does not react with the refrigerant. Acid fluxes are permissible only if the residues are completely removed solvent R-646 or acetone otherwise the risk of system clogging increases 3-4 times.

⚠️ Attention: When soldering tubes with oil residues (for example, after a compressor), the flux may foam. In this case, it is necessary to first clean the surface isopropyl alcohol or a special degreaser Loctite 7063.

3. Temperature conditions and equipment for soldering

Soldering temperature depends on the type of solder and the thickness of the tube. For soft solders (Sn-Pb, Sn-Cu) 200–300°C is sufficient, for hard solders (Ag, CuP) — 600–900°C. Overheating of copper leads to its annealing and loss of strength, therefore it is important to control the temperature. Tools used:

• 🔥 Burner: for soft soldering is suitable propane torch (for example, Rothenberger Super Fire), for solid - acetylene or MAF-gas (for example, Kemper 1500).
• 🔧 Soldering station: for precise work with thin tubes (for example, Weller WX 2010 with a nozzle for soldering copper).
• 🌡️ Thermocouple or infrared thermometer: for temperature control (critical when working with inverter compressors).
• 🧲 Flux applicator: for applying flux to the inner surface of the tube (for example, stainless steel brush).

When soldering thin-walled tubes (0.6–0.8 mm) the maximum temperature should not exceed 350°C —otherwise copper will lose its hardness. For control, use thermal paint (for example, Tempilaq), which changes color when a critical temperature is reached. When working with silver-containing solders, heating should be uniform to avoid thermal stress in the seam. data-i="181">maximum temperature should not exceed 350°C

4. Step-by-step instructions: how to solder a copper tube of a refrigerator

Let's consider the soldering process using the example of repairing a leak in capillary tube (diameter 0.6–0.8 mm) using lead-free solder Sn97Cu3 and acid-free flux FIM.

Scrub the tube with sandpaper (grain 400–600)|Degrease the surface with isopropyl alcohol|Apply a thin layer of flux (avoid excess)|Prepare solder and torch (check gas pressure)|Protect adjacent parts with asbestos sheet-->

Step 1. Surface preparation

Clean the area soldering sandpaper (grain size 400–600) until shiny, then degrease isopropyl alcohol. For internal cleaning of the tube, use brushmoistened with flux. If the tube is heavily oxidized, treat it 5% hydrochloric acid solution (only for external use). surface!).

Step 2. Application flux

Apply flux FIM with a brush or applicator. For tubes with a diameter of less than 1 mm, 1-2 dropsis sufficient. Avoid getting flux inside - this may clog the capillary. When soldering condenser or evaporator use flux-paste for precise application.

Step 3. Heating and soldering

Heat the tube with a torch to the melting temperature of the solder (for Sn97Cu3 - 220–240°C Touch the solder rod to the joint - it should). melt and flow evenly into the gap. Do not overheat the copper: if it turns cherry red (more than 700°C), let it cool and start again.

Step 4. Cooling and checking

After soldering, let the seam cool naturally (do not cool with water!) Check. tightness soap solution under a pressure of 10–15 atm. If bubbles appear, repeat soldering. For systems with R600a is required. data-i="225">halogen leak detector checking with a soap solution halide leak detector.

⚠️ Attention: When soldering tubes NoFrost-systems (for example, in refrigerators Atlant or Indesit), avoid getting solder on the aluminum parts of the evaporator - this will cause electrochemical corrosion. Use mica protective screen.

5. Typical mistakes and how to avoid them

Even experienced craftsmen sometimes make mistakes that lead to repeated leakage or breakdown of the refrigerator. Here are the most common:

• 🔴 Overheating of the tube: leads to annealing of copper and brittleness of the seam. Solution: use a torch with piezo ignition and flame adjustment, heat the tube to 200–250°C (for soft solders).
• 🔴 Insufficient cleaning: the oxide film prevents solder adhesion. Solution: clean the tube sandpaper immediately before soldering, and not in advance.
• 🔴 Use of acid flux without rinsing: residues cause corrosion. Solution: wash the seam hot water with soda (10 g/l), then dry.
• 🔴 Soldering under refrigerant pressure: gas interferes with the formation of the seam. Solution: bleed off the freon through service port before soldering.
• 🔴 Wrong choice of solder: for example, POS-61 for systems s R600a. Solution: use lead-free or silver-containing solders for modern refrigerators.

The error with incomplete soldering of the seam is especially dangerous - when the solder has not completely filled the gap. In this case, microcracks will lead to leakage in 1-2 months. To avoid this, use capillary effect: heat the tube from below, and apply solder from above - so it will evenly flow into the joint.

What will happen if you solder without flux?

Without flux, the oxide film on the copper prevents the adhesion of the solder to the surface. The seam will be porous and weak, and the risk of repeated leakage will increase by 5–7 times. In addition, when heated, the copper actively oxidizes, which further deteriorates the quality of soldering in refrigeration systems, which can lead to scale getting into the compressor and jamming. data-i="274">6. Features of soldering in different types of refrigerators

6. Features of soldering in different types of refrigerators

The design of the refrigerator affects the choice of soldering technology. Let's consider the key differences:

• 🧊 Conventional (drip) refrigerators: the tubes are thicker (1-1.5 mm), allow the use of POS-61 or Sn97Cu3. The main difficulty is access to evaporatorwhich is often hidden by polyurethane foam.
• ❄️ NoFrost systems: thin tubes (0.6–0.8 mm) and aluminum evaporators. They require precise temperature control. When soldering, avoid contact of solder with aluminum. acid-free flux and precise temperature control. When soldering, avoid getting solder on the aluminum.
• 🔄 Inverter compressors: vibrations place increased demands on the strength of the seam. Optimal silver-containing solder (for example, Ag15) or CuP6 for critical areas.
• 🔋 Refrigerators on R600a: isobutane leaks through microcracks, so the seam must be sealed. Use vacuum leak detector to check.

In two-chamber refrigerators (for example, Samsung RB37 or LG GA-B489) you often have to solder interchamber jumper a thin tube connecting the freezer and refrigerator compartments. Accuracy is critical here: overheating can damage it. data-i="301">or thermostat or defrost sensor. For such work, use soldering station with a thermostat.

⚠️ Attention: In refrigerators with linear compressor (for example, Bosch KAN92VI30R), soldering tubes near the motor requires its dismantling - otherwise there is a risk of damage to the windings from overheating.

7. How to check the quality of soldering

Even a seemingly perfect seam can have microdefects. To check, use a combination of methods:

• 🔍 Visual inspection: the seam must be smooth, without cracks and pores. Color - uniform (without dark spots indicating oxidation).
• 🫧 Soap solution: apply to the seam under a pressure of 10-15 atm. Bubbles will indicate a leak. R600a this method is ineffective - necessary electronic leak detector.
• 📉 Vacuum test: pump out the system until –0.9 atm and observe for 10-15 minutes. If the pressure rises, there is a leak.
• 🔬 Ultrasonic flaw detector: used in service centers to detect microcracks (for example, a device Sonotest Master).

For home repairs soap solution and vacuum test. If the refrigerator does not freeze after soldering, check:

1. Tightness service port (often leaks after connecting the pressure gauge).
2. Condition filter-drier —if it overheats, it may clog.
3. Pressure in the system (normal for R134a: 4–6 atm discharge, 0.5–1 atm suction).

Frequently asked questions (FAQ)

Is it possible to solder copper tubes of a refrigerator with a regular soldering iron?

Technically it is possible, but only for tubes with a thickness of 1 mm and using powerful soldering iron (100–150 W) with a copper tip. However, for thin-walled tubes (0.6–0.8 mm), the soldering iron will not provide uniform heating - it is better to use gas torch or soldering station. Also, the soldering iron is not suitable for silver-containing soldersas it does not develop the required temperature (600–800°C).

Which solder is better for a refrigerator with R600a freon?

For R600a (isobutane), the tightness of the seam is critical, since gas molecules are smaller than those data-i="355">, and seep through micropores. Optimal solders: R134a, and seep through micropores. Optimal solders:

• Sn97Cu3 (lead-free) - for thin tubes (0.6–0.8 mm);
• Ag5 or Ag15 (silver-containing) - for critical areas (for example, connection to a compressor);
• CuP6 (phosphorus-copper) - for thick-walled tubes (from 1 mm), but requires high temperature.

Strongly not recommended POS-61 (lead) - it can react with isobutane and clog the system.

How to clean the old tube solder before soldering?

To remove old solder, use:

1. Mechanical method: stripping emery paper (grain 400–600) or scraper.
2. Chemical method: apply soldering acid (for example FKSp) for 1-2 minutes, then rinse with water. For thin tubes it is better to use gel flux cleaner (for example, Würth 890.3).
3. Thermal method: heat the tube with a torch until the old solder melts and remove it copper braid.

After cleaning, be sure to degrease the surface isopropyl alcohol.

Is it possible to solder a refrigerator tube without flux?

Theoretically, it is possible if you use self-fluxing solders (for example, CuP6), but in practice this is fraught:

• Poor quality of the seam due to the oxide film;
• Risk of repeated leakage after 1–3 months;
• Overheating of copper (when trying to “burn through” the oxides with a torch).

Exception - soldering new copper tubes in an inert environment (for example, under a layer argon), which is impossible at home.

How much does it cost to solder refrigerator tubes at the service center?

The cost depends on the type of repair and the region:

• Replacement of the capillary tube: 3,000–6,000 rubles;
• Soldering leaks in the condenser: 2,500–4,500 RUB;
• Evaporator repair (NoFrost): 4,000–8,000 RUB;
• Refilling with freon after soldering: 1,500–3,000 rub.

The price usually includes diagnostics, soldering, evacuation and refrigerant charging. In some services (for example, for refrigerators Liebherr or Miele) the price may be higher. 20–30% due to the use of original parts.