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Solder pastes

Best-in-class thermal performance, flexibility, reflow and reliability

AVAILABLE DIRECTLY AT CAPLINQ.COM

Solder Pastes

Solder paste is a mixture of powdered solder and a flux, used in surface mount technology (SMT) to create electrical connections between components and a printed circuit board (PCB). The flux helps to clean and protect the metal surfaces during soldering, while the solder powder melts and creates a bond between the components and the board. It is applied on a PCB with the help of a stencil or a foil. The stencil accurately deposits the right amount of paste on the surface mount pads. It should be properly aligned on the circuit board. Solder paste application is one of the most important aspects of component mount process in PCB assembly. 

At Caplinq, we understand the importance of reliable electrical connections in today's demanding electronics landscape. That's why we're proud to offer a comprehensive selection of best-in-class solder pastes, meticulously formulated to deliver exceptional performance and unwavering reliability. Solder paste is the cornerstone of surface mount technology (SMT), creating the critical electrical and mechanical connections between electronic components and printed circuit boards (PCBs).

Experience optimal printability with our precisely formulated pastes, featuring tailored viscosities and particle sizes for consistent, high-definition deposits. Achieve robust and reliable solder joints with our pastes' exceptional wetting characteristics, ensuring maximum contact area and electrical conductivity. Benefit from long-lasting performance with our high-quality alloys and advanced flux technology, delivering resilience in even the most demanding applications. Enjoy streamlined processes with our diverse range of solder paste options, including no-clean and clean formulations to optimize your production efficiency. Ready to elevate your SMT experience? Explore Caplinq's range of best-in-class solder pastes and discover the difference that comes with partnering with an adhesive expert.

 

25 products

Product selector guide

Solder pastes
Product Description Alloy Particle size distribution Viscosity  (mPA.s) Melting temperature Shelf life
Dispensable
DA 100 Tin antimony, dispense solder paste for Die attach 92A Type 4 300,000 242°C 12 months at -20°C
GC 50 Room temp stable, Jet dispensable and fine particle paste for small components SAC305 Type 5 110,000 217°C  180 days in RT
Printable
Loctite GC 10 Room temp stable, Multi purpose solder paste for PCB assembly SAC305 Type 3, 4, 5 200,000 217°C 12 months in RT
Loctite GC 18 Room temp stable, low voiding paste for large area components such as QFN with heat sink. SAC305  Type 4 250,000 217°C 180 days in RT
Loctite HF 212 Refrigerated, Halogen-free, solder paste for PCB assembly 90iSC
97SC		 Type 4 175,000 205 - 218°C 180 days at 0°C - 10°C
Loctite LF 318 Refrigerated, High reliability solder paste for PCB assembly. Both printable and dispensable versions. 90iSC Type 3 650,000 205 - 218°C 180 days at 0°C - 10°C

 

Solder pastes
Product Description Alloy Particle size distribution Viscosity  (mPA.s) Melting temperature Shelf life
LINQALLOY Sn42Bi57Ag1 Low eutectic solder paste for LED Assembly Sn42Bi57Ag1 Type 3, 4 - 138°C 6 months at 5°C
LINQALLOY SP-SAC105 Pb-free solder paste designed for Surface Mount Technology (SMT) SAC105 Type 3, 4, 5 200 223°C  6 months at 5°C
LINQALLOY SP-PSA525 High lead solder paste designed for clog-free dispensing die attach processes Pb92.5Sn5Ag2.5 Type 3, 4, 5 130 - 170 287°C  6 months at 5°C
LINQALLOY SP-SAC305 Pb-free solder paste designed for Surface Mount Technology (SMT) SAC305 Type 3, 4 160 - 230 217°C  6 months at 5°C
LINQALLOY SP-SAC307 Pb-free solder paste designed for Surface Mount Technology (SMT) SAC307 Type 3, 4, 5 190 - 230 220°C  6 months at 5°C

 

▶ Macdermid Alpha Solder Paste Selection Guide (Click here to expand)
Macdermid Alpha Solder Paste
Product Alloy Type Flux Type Halogen Content Flux Classification Shelf Life (months) Stencil Life (Hours) Alloy Features
Kester EP256HA Leaded No-Clean Halogenated ROL1 6 8+ Sn63Pb37, Sn62Pb36Ag2, Sn43Pb43Bi14 Excellent Printing, wide process window, high flux activity
Kester EP256 Leaded No-Clean Halogenated ROL1 6 8+ Sn63Pb37, Sn62Pb36Ag2 and Sn43Pb43Bi14 Excellent Printing, wide process window
Kester NXG1 (Leaded) Leaded No-Clean Halogenated ROL1 8 >8 Sn63Pb37 Premium leaded, next gen reliable shiny fine pitch printing
Kester R276 (Leaded) Leaded No-Clean Zero-Halogen ROL0 6 8+ Sn63Pb37, Sn96.5Ag3Cu0.5, Sn43Pb43Bi14, Sn10Pb88Ag2, Sn95.5Ag3.8Cu0.7, Sn62Pb36Ag2 Excellent dispensing, leaded
Kester FL250D Leaded No-Clean Zero-Halogen ROL0 4 8+ Sn63Pb37, Sn62Pb36Ag2 Automotive grave, easy post-soldering process chemicals
NP545 (Leaded) Leaded No-Clean Zero-Halogen ROL0 12 8+ SAC305 High shelf life, reliable fine‑pitch printing
Alpha OM-5100 Leaded No-Clean Zero-Halogen ROL0 6 >8 Sn63Pb37, Sn62Pb36Ag2, Sn95.5Ag3.8Cu0.7, Sn62.8Pb36.8Ag0.4 Universal Tin-Lead, Wide Process Window
Alpha OM-5300 Leaded No-Clean Zero-Halogen ROL0 6 >8 Sn63Pb37, Sn62Pb36Ag2, Sn62.8Pb36.8Ag0.4 Universal Tin-Lead Solder Paste
Kester R231 Leaded Rosin Halogenated ROL0 4 8 Sn63Pb37, Sn62Pb36Ag2 RMA solder Paste for long Stencil/Print life
Kester R276 (Lead-Free) Leaded Water-Soluble Halogenated ROL0 6 8+ Sn63Pb37, Sn96.5Ag3Cu0.5, Sn43Pb43Bi14, Sn10Pb88Ag2, Sn95.5Ag3.8Cu0.7, Sn62Pb36Ag2 Excellent dispensing, lead-free
Kester R500 (Leaded) Leaded Water-Soluble Halogenated ORM0 6 8 Sn63Pb37 Leaded, consistent dot dispensing, high flux activity
Kester R560 Leaded Water-Soluble Zero-Halogen ORH0 6 8 Sn63Pb37, Sn62Pb36Ag2 Low Voiding (<5%) and good Metallization, high temperature/humidity resistance
Kester R562 Leaded Water-Soluble Zero-Halogen ORM0 6 12 Sn63Pb37, Sn62Pb36Ag2 Low Voiding (<3%) and good Metallization, high temperature/humidity resistance
Kester HM531 Leaded Water-Soluble Zero-Halogen ORM0 6 8+ SnP63Pb37, Sn62Pb36Ag2 Excellent Printing, long Stencil/Print life, High Manufacturability and Metallization (wetting)
Kester NXG1 (Lead-Free) Lead-Free No-Clean Halogenated ROL1 8 >8 SAC305 Premium, next Gen reliable shiny fine pitch printing
Kester EM907 Lead-Free No-Clean Halogenated ROL1 4 12+ SAC305, Sn96.5Ag3.5 Halogenated, lead-free paste joint similar to SnPb performance
Kester NP545 (Lead-Free) Lead-Free No-Clean Zero-Halogen ROL0 12 8+ SAC305 NXG, general high‑performance, versatile, long shelf life
Kester EM918 Lead-Free No-Clean Halogenated ROL0 6 >8 SAC305, Sn96.5Ag3.5 Non-halogenated, lead-free, similar to SnPb performance, wider processing window
Kester NP575-KAP Lead-Free No-Clean Zero-Halogen ROL0 6 >8 SAC305 NXG, maximum flexibility & reliability futomotive, aerospace, or demanding environments
Kester NP505-HR Lead-Free No-Clean Zero-Halogen ROL0 12 8 SAC305 NXG, High reliability, Harsh environments for residue reliability and low voiding
Kester NP505-LT Lead-Free No-Clean Zero-Halogen ROL0 6 12 SAC305, Sn42Bi57Ag1 NXG, low temperature reflow, for temp. sensitive substrate or component
Kester NP510-LT-HR-L1 Lead-Free No-Clean Zero-Halogen ROL0 6 8 HRL1 NXG, low temperature reflow, High reliability
Kester EM919G Lead-Free No-Clean Zero-Halogen ROL0 6 12+ SAC305 NXG, longer shelf life for high volume manufacturing and ultra fine pitch
Kester NP560 Lead-Free No-Clean Zero-Halogen ROM0 6 8 SAC305 Ultra‑low voiding under QFNs, reliable fine‑pitch printing
Alpha JP-500 Lead-Free No-Clean Zero-Halogen ROL0 6 NA SAC305, SAC405 Jetting Solder Paste
Alpha JP-501 Lead-Free No-Clean Zero-Halogen ROL0 6 NA Sn42Bi57.6Ag4 Jetting Solder Paste, Low melting point alloy
Alpha OM-340 Lead-Free No-Clean Zero-Halogen ROL0 6 8 SAC305, SAC405, Sn96Ag4, SACX® Plus 0307, SACXPlus 0807,
Innolot		 Increased Spread Wetting, High Reliability, Low HIP
Alpha CVP-390 Lead-Free No-Clean Zero-Halogen ROL0 6 >8 SAC305, SACX Plus™0307, SACX Plus™ 0807, InnoLot™ High reliable fine‑pitch printing, High Soak Profile, Paste in Through Hole
Alpha CVP-390V Lead-Free No-Clean Zero-Halogen ROL0 6 >8 SAC305 and Innolot alloys Higher reliable fine‑pitch printing, High Soak Profile, Paste in Through Hole
Alpha CVP-520 Lead-Free No-Clean Zero-Halogen ORH0 4 >8 SAC305 Low melting point alloy, Excellent paste in through hole performance, for PV Applications
Alpha OM-353 Lead-Free No-Clean Zero-Halogen ROL0 6 mo >8 SAC305, SACX Plus 0307, InnoLLot Enabling Ultra-Fine Feature Printing
Alpha OM-535 Lead-Free No-Clean Zero-Halogen ROL0 6 mo >8 SBX02, SnBi0.4Ag, 42Sn57Bi1Ag Low Melting Point, High Mechanical Strength and Drop Shock Performance for PV Applications
Alpha OM-362 Lead-Free No-Clean Zero-Halogen ROL0 4 8 SAC305, Innolot High Reliability, Ultra Low Voiding
Alpha OM-100 SnCX07 Lead-Free No-Clean Zero-Halogen ROL0 6 16 SnCX07 Lower cost than SAC base, reliable fine‑pitch printing and thermal cycling
Alpha OM-565 HRL3 Lead-Free No-Clean Zero-Halogen ROL0 6 8 HRL3 High Reliability, outperforms SAC305 in thermal cycling and mechanical strain
Kester EM808 Lead-Free Water-Soluble Halogenated ORH1 6 8+ SAC305, Sn96Ag4 Prints consistently, wets aggressively
Kester EM828 Lead-Free Water-Soluble Halogenated ORH1 6 >8 SAC305 Low-voiding, prints consistently, wets aggressively
Kester R500 (Lead-Free) Lead-Free Water-Soluble Zero-Halogen ORM0 6 8 SAC305 Consistent dot dispensing, high flux activity
Kester R520A Lead-Free Water-Soluble Zero-Halogen ORH0 4 >8 SAC305 High flux activity for excellent wetting, fine‑pitch printing
Kester WP616 Lead-Free Water-Soluble Zero-Halogen ORM0 6 8+ SAC305 High Reliability, excellent Printing
Alpha WS-826 Lead-Free Water-Soluble Zero-Halogen ORM0 6 8 SAC305 Excellent Cleanability, stencil life, reliable under high humidity and temperature

 

Frequently asked questions

Frequently asked questions about Soldering Materials

What is Solder Paste Reflow?

Solder paste reflow is the process of heating the PCB with the applied solder paste to melt the solder and create electrical connections between the components and the PCB. The reflow profile, which includes the temperature ramp-up, dwell time, and cooling rate, is crucial for achieving good solder joint quality.


What is the difference between IR reflow and conventional reflow?

Both conventional oven reflow and infrared (IR) reflow are common methods for soldering surface mount components (SMCs) to printed circuit boards (PCBs). Conventional ovens use hot air to heat the board, while IR reflow uses infrared radiation. Conventional ovens are cheaper, widely available, and suitable for various PCB sizes and component densities, but they can be slower and have uneven heating. IR reflow offers faster heating, more uniform temperatures, and less thermal shock to components, but it's generally more expensive.

 

What is Solder Paste Printing?

Solder paste printing is the process of applying solder paste to a PCB using a stencil and a squeegee. The squeegee applies pressure to the paste, forcing it through the openings in the stencil onto the PCB pads. The stencil's thickness and the openings' size and shape are critical factors in achieving consistent and precise solder paste placement. The printing process is critical for achieving consistent and accurate solder paste placement.

 

What is the Role of Flux Activity in Solder Paste?

Flux activity refers to the chemical reactivity of the flux in the paste. A more active flux can clean surfaces more effectively but may also be more corrosive. The choice of flux activity depends on the specific application and the materials being soldered.

 

Do the flux residue need to be removed?

The need to remove flux residue after an SMT process depends on the type of flux used.

  • No-clean flux: These fluxes are designed to leave a non-corrosive residue that does not require cleaning. They are often preferred in applications where cleaning can be time-consuming or introduce contamination risks.

  • Water-soluble flux: These fluxes require cleaning with water or a water-based cleaning solution to remove the residue. They are often used when the residue could potentially cause corrosion or interfere with subsequent processes.

  • Solvent-soluble flux: These fluxes require cleaning with a solvent-based cleaning solution. They are less commonly used due to environmental concerns and the potential for solvent residues to remain on the PCB.

 

How Does Particle Size Affect Solder Paste?

Particle size refers to the average diameter of the solder powder particles in the paste. Smaller particles can provide finer detail and better wetting, but they may also be more susceptible to oxidation and require more careful handling. Larger particles, on the other hand, can be easier to handle but may not provide the same level of detail.

 

What is the Viscosity of Solder Paste?

Viscosity measures the resistance of a fluid to flow. In solder paste, it's a crucial property that affects how the paste spreads and flows during application through the stencil apertures. Higher viscosity pastes are thicker and may require more pressure to apply, while lower viscosity pastes are thinner and flow more easily. The viscosity range of printing solder paste is about 100-200Pa.s, which is required to adjust for different scenarios.

 

What is Solder Paste Inspection (SPI)?

Solder paste inspection is the process of examining the applied solder paste for defects such as voids, bridging, and insufficient volume. Visual inspection and automated optical inspection (AOI) are common methods for solder paste inspection. Refer to the full PCB Assembly Process Flow to understand more about the solder paste inspection. 


 

How Does Solder Paste Temperature Affect Solder Joint Quality?

The temperature at which the solder paste is reflowed is critical for achieving good solder joint quality. If the temperature is too low, the solder may not melt completely, resulting in weak or incomplete joints. If the temperature is too high, the solder may become overly fluid, leading to excessive wetting or bridging.

 

Learn more

Solder Paste Classification

By Size
Type 1
Type 2
Type 3
Type 4
Type 5
Type 6
Type 7
Type 8
By Flux
Flux Type
Rosin
Water Soluble
No Clean
Flux Activity
Low
Medium
High
Halogen Content
Halogenated
Non-Halogenated
By Material
Leaded
Lead-Free

By Solder Paste Particle Size

Particle size plays a pivotal role in solder paste performance, affecting print resolution, wetting efficiency, and process reliability. Finer powders support high-density, fine-pitch applications but are more susceptible to oxidation, while coarser powders enhance process robustness at the expense of print precision. The appropriate particle size is determined by the specific application requirements, including:

🔬
Component Size & Pitch
Fine-pitch and miniaturized components require finer particle sizes for accurate deposition and effective stencil release.
📐
PCB Design
Complex and high-density PCB layouts demand precise paste control, making finer powders essential for consistent printing.
⚙️
Soldering Process
Reflow profiles and stencil thickness influence particle size selection, balancing print quality and process stability.
✅
Reliability Requirements
High-reliability applications benefit from finer powders due to improved wetting and stronger solder joint formation.

 

Solder Paste Particle Sizes
Powder Type Particle Size > 80% Min Stencil Aperture (5-ball rule) Surface Area Ratio
µm Mil µm Mil
Type 1 75–150 6–3 Not used in modern SMT
Type 2 45–75 3–1.8 380 15.0 1.5–2
Type 3 25–45 1.8–1.0 230 9.0 1.2–1.5
Type 4 20–38 1.5–0.8 190 7.5 1.0–1.2
Type 5 15–25 1.0–0.6 130 5.0 1.5–2.0
Type 6 5–15 0.6–0.2 76 3.0 Varies
Type 7 2–11 0.4–0.08 56 2.2 Varies
Type 8 2–8 0.3–0.08 Varies Varies Varies

 

Aperture



The image showcases three common aperture shapes used in stencil printing: Circle, Square, and Squircle. These apertures are openings in the stencil through which solder paste is dispensed onto the printed circuit board (PCB). Circle: A classic and widely used shape, offering a clean and symmetrical solder deposit. Square: Often used for larger components or when a more rectangular pad shape is required. Squircle: A hybrid shape between a circle and a square, balancing circular and square characteristics.

All apertures in this image are 1:1 with the pad design, meaning their dimensions match the corresponding pad on the PCB. This ensures optimal solder paste placement and reduces the risk of defects like bridging or voids.
The 5-ball rule is a simple guideline used in electronics manufacturing to estimate the optimal particle size of solder paste for a given stencil aperture. It states that the diameter of the solder paste particles should be approximately 5 times smaller than the smallest dimension of the stencil aperture. It will certainly help in preventing solder bridging, improve soldering print quality and enhance wetting.

The 5-ball rule is a valuable tool for manufacturers as it provides a quick and easy way to estimate the appropriate solder paste particle size for a given PCB design. However, it's important to note that this is a general guideline, and there may be exceptions depending on specific factors such as component density, stencil thickness, and soldering process. While the 5-ball rule is a useful starting point, manufacturers should also consider conducting experiments and testing different particle sizes to determine the best fit for their specific application.
5-ball-rule
Area Ratio
In solder paste printing, aspect ratio and area ratio are critical design parameters that determine how effectively solder paste releases from the stencil aperture, directly impacting print quality and consistency
 

Aspect Ratio
Aspect Ratio = Aperture Width / Stencil Thickness
Defined as the ratio of stencil thickness to aperture width.
A minimum aspect ratio of ≥ 1.5 is generally recommended to ensure reliable paste release from the stencil aperture.


Area Ratio
Area Ratio = (Aperture Area) / (Aperture Perimeter × Stencil Thickness)
Defined as the ratio of aperture opening area to the stencil wall area.
A minimum area ratio of ≥ 0.66 is typically required to achieve consistent paste transfer and avoid deposition defects.



By Solder Paste Flux

Flux is used to remove oxides, prevent re-oxidation, and improve wetting to ensure reliable solder joint formation. The IPC J-STD-004C standard classifies fluxes based on composition (rosin, resin, organic), activity level (low, moderate, high), and halogen content. These parameters define the flux’s cleaning capability, wettability, and residue characteristics, forming a complete designator for selection and control.

Solder materials are broadly categorized as Clean (water-soluble) and No-Clean. Clean fluxes are more chemically active and require post-solder cleaning, while No-Clean fluxes leave minimal residue and typically do not require cleaning. However, in high-reliability or high-performance applications—such as high-speed electronics, underfill processes, or cosmetic-sensitive assemblies—even No-Clean residues may be removed.

Halide-containing fluxes are easier to clean but leave more residues, whereas halide-free No-Clean fluxes produce minimal residue but often require specialized cleaning solutions when removal is necessary.

Flux Composition
Flux Composition Partial Activity Partial With Halides No Halides
Rosin RO Low ROL ROL1 ROL0
  Moderate ROM ROM1 ROM0
  High ROH ROH1 ROH0
Resin RE Low REL REL1 REL0
  Moderate REM REM1 REM0
  High REH REH1 REH0
Organic OR Low ORL ORL1 ORL0
  Moderate ORM ORM1 ORM0
  High ORH ORH1 ORH0
Inorganic IN Low INL INL1 INL0
  Moderate INM INM1 INM0
  High INH INH1 INH0

Presentations

General Understanding on Fluxes

This presentation provides a comprehensive introduction to fluxes used in electronics soldering and PCB assembly. It explains the functions of flux, different flux chemistries, activation mechanisms, and residue classifications, while discussing their impact on solderability, joint reliability, cleaning requirements, and overall manufacturing performance.

By Solder Paste Material

Solder paste can be classified based on its material composition, primarily into lead-containing and lead-free types.

What is a Lead Solder?


Lead solder is a metallic alloy primarily composed of lead (Pb) and tin (Sn), often with small amounts of other elements like antimony (Sb) or copper (Cu). Historically, these alloys have been used to join metals by melting the solder and allowing it to solidify between the pieces. Compared to other metal alternatives, lead solder cools more slowly. This reduces the chance of the joint breaking and is effective in wetting joints. Lead solder has a lower and precise melting point, making it easier to control in automated PCB assembly and less likely to damage electronic components during the soldering process.

 

What is a Lead-Free Solder?


Lead-free solder is a metallic alloy used for joining metals that does not contain lead (Pb). It's made without harmful lead and uses metals like tin, copper, silver, bismuth, or antimony. These alloys are designed to replace traditional lead-based solders due to the environmental and health concerns associated with lead.

Compared to lead-based solders, lead-free solders typically have higher melting temperatures, requiring adjustments in soldering processes. Lead-free solders often exhibit different mechanical properties, such as higher strength and hardness, compared to lead-based solders.

Some common lead-free combinations include Tin-Silver-Copper (SnAgCu) alloy, Tin-Copper (SnCu) alloy and Tin-Bismuth (SnBi) alloy. Choosing the right lead-free solder depends on the specific needs of the electronic product. Factors like component compatibility, thermal cycling requirements, and joint reliability need to be carefully considered when selecting a lead-free solder.

 

What is the Reflow Profile of a Solder?

Reflow-Profile-SAC305

A reflow profile is a specific temperature sequence that a PCB with applied solder paste is subjected to in order to melt the solder and create electrical connections between components and the PCB. The standard reflow profile has four zones: preheat, soak, reflow and cooling. The profile in the picture above will serve as a typical reference [benchmarking SAC305 solder paste reflow profile] and describe the ideal temperature curve of the top layer of the PCB.

Reflow Profile Overview

A reflow profile defines the thermal process used to form reliable solder joints through controlled heating and cooling stages.

🔥
Preheat
Gradual heating (≈150–180°C) prevents thermal shock and activates flux for improved wetting.
→
⏳
Soak
Temperature equalization (60–120s) ensures uniform heating across all components.
→
🌡️
Reflow
Peak temperature exceeds melting point (TAL ~30–40s), forming solder joints and IMC layers.
→
❄️
Cooling
Controlled cooling (<4°C/s) solidifies solder and ensures joint strength and reliability.
 

Solder Alloys Properties

The chart organizes solder alloys by material type and temperature range, with key alloy families highlighted for quick reference and selection.

Solder Alloy Classification

Lead-Based (SnPb)
Low melting (~183°C), excellent wetting and reliability
Low / Medium Temperature
SnPb
High Temperature (>300°C)
High-Pb
Lead-Free (RoHS)
Environmentally compliant alloys with higher melting range
Low Temperature (<183°C)
SnBi
Medium Temperature (217–227°C)
SAC SnCu
High Temperature (>300°C)
SnSb

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