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Indium NC-SMQ51SC Solder Paste

NC-SMQ®51SC is an air reflow, no-clean solder paste designed for use in a wide range of environmental conditions. It has exceptional stencil life and tack strength, and offers consistent print definition even in ultra-fine pitch applications. NC-SMQ51SC’s wide processing window allows it to be used with standard eutectic Sn/Pb, Sn/Pb/Ag and high temperature alloys including Au/Sn, Pb/Sn and Pb/Sn/Ag.
Manufacturer: Indium
Description

Benefits

• Wide reflow process window
• Consistent fine pitch print deposition
• Extended open time
• Superior tack strength
• No-clean residue
• Exceptional wetting in air reflow

Introduction

NC-SMQ®51SC is an air reflow, no-clean solder paste designed for use in a wide range of environmental conditions. It has exceptional stencil life and tack strength, and offers consistent print definition even in ultra-fine pitch applications. NC-SMQ51SC’s wide processing window allows it to be used with standard eutectic Sn/Pb, Sn/Pb/Ag and high temperature alloys including Au/Sn, Pb/Sn and Pb/Sn/Ag.

Alloys

Indium Corporation manufactures low-oxide spherical solder powder composed of Sn/Pb and Sn/Pb/Ag in a standard type 3 mesh size (J-STD-006). Other non-standard mesh sizes are available upon request. The weight ratio of the solder powder to solder paste is referred to as the metal load and is typically in the range of 82-91% for standard alloy compositions.

Standard Product Specifications

Packaging

Standard packaging for stencil printing applications includes 4oz. jars and 6oz. or 12oz. car tridges. Packaging for enclosed print head systems is also readily available. For dispensing applications, 10cc and 30cc syringes are standard. Other packaging options may be available upon request.

Storage and Handling

Procedures

• NC-SMQ51SC has a shelf life of 6 months when stored at <10°C.
• When storing solder paste packaged in syringes or car tridges, they should be stored tip down to prevent excessive flux separation.

Packaging Type

Time Interval (Hours)

10cc/30cc Syringes

2

4oz. Jars/6oz. Car tridges

4

12oz. Car tridges/ Enclosed Print Head Cassettes

6

Enclosed Print Head Systems

24

• If refrigerated, the following minimum time inter vals should be adhered to for the solder paste to gradually arrive at ambient room temperature before use.

• Solder paste temperature should be verified before use to prevent the use of cold solder paste that can result in poor printing and reflow per formance.

• The time and date of removal from refrigerated storage and opening should be clearly marked on the container.

Material Safety Data

Sheets

The MSDS for this product can be found online at
http://www.indium.com/techlibrar y/msds.php

BELLCORE AND J-STD TESTS & RESULTS

J-STD-004 (IPC-TM-650)

• Flux Type Classification ROL1

• Flux Induced Corrosion

(Copper Mirror) Pass

• Presence of Halide:

Silver Chromate Pass

Fluoride Spot Test Pass

Cl Equivalent <0.019% of paste

• Post Reflow Flux Residue

(ICA Test) 47%

• Corrosion Pass

• SIR Pass

• Typical Acid Value 85

 

J-STD-005 (IPC-TM-650)

• Typical Solder Paste Viscosity (Sn63/Pb37, Type 3) Brookfield (5 rpm)

90% Metal Load 850 kcps

90.5% Metal Load 1100 kcps

Malcom (10 rpm)

90% Metal Load 1800 poise

• Typical Thixotropic Index; SSF -0.60

• Slump Test Pass

• Solder Ball Test Pass

• Typical Tackiness 38 grams

• Wetting Test Pass

• Bellcore Electromigration Pass

Printing

Stencil Design:

Electroformed and laser cut/electropolished stencils produce the best printing characteristics among stencil types. Stencil aper ture design is a crucial step in optimizing the print process. The following are a few general recommendations:

• Discrete components — A 10-20% reduction in stencil aper ture area has significantly reduced or eliminated the occurrence of solder beads. The “home plate” design is a common method for achieving this reduction.

• Fine pitch components — A sur face area reduction is recommended for aper tures of 20 mil pitch and finer. This reduction will help minimize solder balling and bridging that can lead to electrical shor ts. The amount of reduction necessar y is process dependent (5-15% is common).

• A minimum aspect ratio of 1.5 is suggested for adequate release of solder paste from stencil apertures. The aspect ratio is defined as the width of the aperture divided by the thickness of the stencil.

Printer Operation:

The following are general recommendations for stencil printer optimization. Adjustments may be necessar y based on specific process requirements:
• Solder Paste Bead Size: 20-25mm diameter
• Print Speed: 25-50mm/sec.
• Squeegee Pressure: 0.018-0.027kg/mm of blade length
• Underside Stencil Wipe: Once ever y 10-25 prints
• Solder Paste Stencil Life: >8 hrs. @ 30-60% R.H. & 22-28°C

Cleaning

NC-SMQ51SC is designed for no-clean applications and leaves a benign, hard residue. If desired, the flux residue can be removed by means of solvent, ultra-sonic, water with saponifier, semi-aqueous, or any proven commercially available cleaning method designed for removal of rosin/ resin based solder paste flux residues.

Stencil Cleaning: This is best-per formed using an automated stencil cleaning system for both stencil and misprint cleaning to prevent extraneous solder balls. Most commercially available stencil cleaning formulations, including isopropyl alcohol (IPA), work well.

Reflow

Recommended Profile:

This profile is designed for use with Sn63/Pb37 & Sn62/Pb36/Ag2 alloys. It will serve as a general guideline in establishing a reflow profile for these alloys. Adjustments to this profile may be necessar y based on specific process requirements and the use of alloys with dif ferent melting temperatures.

Heating Stage:

A linear ramp rate of 0.5°-1°C/second allows gradual evaporation of volatile flux constituents and prevents defects such as solder balling/beading and bridging as a result of hot slump. It also prevents unnecessar y depletion of fluxing capacity when using higher temperature alloys.

Liquidus Stage:

A peak temperature of 25°-45°C (215°C shown) above the melting point of the solder alloy is needed to form a quality solder joint and achieve acceptable wetting due to the formation of an intermetallic layer. If the peak temperature is excessive, or the time above liquidus greater than the recommended 45-90 seconds, flux charring, excessive intermetallic formation and damage to the board and components can occur.

Cooling Stage:

A rapid cool down of <4°C/second is desired to produce a fine grain structure in the solder joint. Slow cooling will form a large grain structure, which will typically exhibit poor fatigue resistance. If excessive cooling (>4°C/second) is used, both the components and the solder joint may be stressed due to a high CTE mismatch.

Compatible Products

• Rework Flux: TACFlux 007

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Unit 7, Orbital 25, Dwight Road, Watford, Hertfordshire
WD18 9DA

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