Solder Composition
Qualitek Sn/Ag/Cu (Tin/Silver/Cu) Alloys are designed as a lead-free alternative for Sn/Pb alloys for electronics assembly (PCB assembly) operations. The Qualitek Sn/Ag/Cu alloys conform and exceed the impurity requirements of J-Std-006 and all other relevant international standards.

Material Safety Data Sheets (MSDS)
798LF Water Soluble Lead Free Solder Paste MSDS

Typical Analysis

Sn

Ag

Cu

Pb

Sb

Bi

In

As

Fe

Ni

Cd

Al

Zn

Au

LF955-38

Bal.

3.3-3.7

0.5-0.9

0.050 Max

0.050 Max

0.050 Max

0.050 Max

0.010 Max

0.010 Max

0.050 Max

0.010 Max

0.010 Max

0.010 Max

0.020 Max

LF958-35

Bal.

3.6-4.0

0.5-0.9

0.050 Max

0.050 Max

0.050 Max

0.050 Max

0.010 Max

0.010 Max

0.050 Max

0.010 Max

0.010 Max

0.010 Max

0.020 Max

LF965-30

Bal.

2.8-3.2

0.3-0.7

0.050 Max

0.050 Max

0.050 Max

0.050 Max

0.010 Max

0.010 Max

0.050 Max

0.010 Max

0.010 Max

0.010 Max

0.020 Max

LF217

Bal.

3.8-4.2

0.3-0.7

0.050 Max

0.050 Max

0.050 Max

0.050 Max

0.010 Max

0.010 Max

0.050 Max

0.010 Max

0.010 Max

0.010 Max

0.020 Max

Sn/Ag/Cu Sn63/Pb37 Melting Point, °C 217-221 183 E Hardness, Brinell 15HB 14HB Coefficient of Thermal Expansion Pure Sn=23.5 24.7 Tensile Strength, psi 4312 4442 Density, g/cc 7.39 8.42 Electrical Resistivity , (µohm-cm) 13.0 14.5 Electrical Conductivity, %IACS 16.6 11.9

Sn/Ag/Cu Sn63/Pb37 Yield Strength, psi 3724 3950 Total Elongation,% 27 48 Joint Shear Strength, at 0.1mm/min 20 C 27 23 Joint Shear Strength, at 0.1mm/min 100 C 17 14 Creep Strength, N/mm2 at 0.1mm/min 20 C 13.0 3.3 Creep Strength, N/mm2 at 0.1mm/min 100 C 5 1 Thermal Conductivity, W/m.K 58.7 50.9

Particle Size
Sn/Ag/Cu alloys are available in Type 2 (75-45µm), 3(45-25µm), 4(38-20µm), and 5 (25-15µm) J-STD-005 powder distribution. Solder powder distribution is measured utilizing laser diffraction, optical analysis and sieve analysis. Careful control of solder powder manufacturing processes ensures the particles’ shape are 95% spherical minimum (aspect ratio < 1.5) and that the alloy contains a typical maximum oxide level of 80 ppm.

Classification of Solder Powders by Particle Size

Powder Type	Fines	Majority		Coarse		Typical Mesh
	<10%	>80%	>90%	<1%	0%
1	20	75-150		150	160	100/200
2	20	45-75		75	80	200/325
3	20	25-45		45	50	325/500
4	20		20-38	38	40	400/635
5	15		15-25	25	30	500
6	5		5-15	15	20

Metal Loading
Typical metal loading for SMT stencil printing application is 88-89.5 %. Compared to typical Sn63/Sn62 solder pastes manufactured with 90% by weight metal loading, DSP798LF Lead Free provides as much as 10-12% higher metal volume than Sn63/Sn62. This increased in volume of DSP798LF promotes better wetting and spreading of Sn/Ag/Cu Lead Free alloy.

Solder Paste
Qualitek has developed a unique flux system designed specifically for high temperature lead free alloys. It provides the fluxing activity levels that promote thermal stability and prevents thermal degradation when reflowing under air atmosphere (normal). Since use of nitrogen is not required, DSP 798LF Lead Free Solder paste will provide excellent cost savings.

In addition, DSP 798LF Lead Free paste exhibits superior joint strength, excellent wettability, extraordinary print definition and tack life.

Main Features

• Low foaming
• Extended stencil life
• Long tack time
• Excellent wettability

PRINTING

SMT Stencils
Use of chemical etched/electroformed SMT stencil is preferred however DSP798LF has been used successfully with chemical etch, electroformed, and laser cut stencils

Squeegee

	Blades:		Metal (stainless steel) squeegee blades angled from 45-60° give the best print definition for PCB assembly. Metal(nickel) squeegee blades angled from 45-60° give the best performance. 90 durometer polyurethane may also be used.
	Pressure:		Pressure should be adjusted at the point where the lead free solder paste leaves a relatively clean SMT stencil after each print pass. Typical pressure setting 0.6-1.5lb per linear inch of blade.
	Speed:		Normal print speeds are 1.0-2.5 (25-50mm) per second. As print speeds increase pressure will need to be increased.

Print Definition
DSP798LF provides excellent print definition characterized by brick-like prints. Good release is seen on 12-9 mil apertures. Tack values are high even after extended open time in both normal and high humidity environments. Refer to data sheet

Open & Abandon Time
Tests have proven that DSP798LF will perform during continuous printing for up to 8 hrs. Field test have shown that an abandon time of at least 1 hr is possible, resulting in a perfect 1st pass print on resumption of printing.

Paste Application
Solder paste should be taken out of the refrigerator at least 3 to 6 hours prior to use. This will give the paste enough time to come to thermal equilibrium with the environment. Also, any fresh jar of paste should be gently mixed for at least one minute with a spatula. Be sure not to mix the paste too vigorously, as this will degrade the paste’s viscosity characteristics and introduce entrapped air into the paste. The purpose of the mixing is to insure that the paste is smooth and consistent. If the paste is supplied in cartridges pre-mixing is not necessary due to the shear action produced from the dispensing.

Reflow
Best results have been acheived when DSP 798LF is reflowed in a forced air convection oven with a minimum of 8 zones (top&bottom), however reflow is possible with a 4 zone oven (top & bottom). Refer to data sheet

CLEANING
DSP798LF is water soluble formulation therefore the residues need to be removed. Residue removal is easily achieved, with the use of hot 60 C (140 F) de-ionized water in either a batch or conveyorized cleaner. Spray pressures so be maintained at 20-30 psi and conveyor speed of 3-6ft/min.

Storage & Shelf Life
It is recommended that lead free solder paste be stored at a temperature of between 35-50 F (2-10 C) to minimize solvent evaporation, flux separation, and chemical activity. If room temperature storage is necessary it should be maintain between 68-77F (20-25 C).

Shelf life
Unopened Container (35-50F/2-10C) 6 months (from DOM)
Unopened Container (68-77F/20-25 C) 1 months (from DOM)
Opened Container (68-77F/20-25 C) 24 hours

Reusing Solder Paste
This is not normally recommended, because it typically generates more problems than it is worth. If you do decide to reuse lead free solder paste, these pointers may be helpful. First, Qualitek recommends putting any used paste in an empty jar, so any fresh paste will not become contaminated. This paste should be tightly sealed and refrigerated. Then, the paste may be reused at a later date, provided that the paste has not separated or thickened significantly compared to its original properties. If you have success in printing the reused paste, the paste is acceptable for use. If significant printing problems occur, discard the paste. You also may want to mix 50% “used” and 50% new to get maximum utility of the paste. This will keep the paste relatively fresh while consuming the used paste.

Working Environment
Solder paste performs best when used in a controlled environment. Maintaining ambient temperature of between 68-77 F (20-25 C) at a relative humidity of 40-65% will ensure consistent performance and maximum life of paste.

Cleaning Misprint Boards
If you should have a misprinted circuit board, the paste may be cleaned off manually with alcohol (IPA) or Qualitek stencil cleaner, SK-11. If you have a more elaborate board cleaner, the paste may be easily removed with use of a 5% saponifier solution in hot DI water. Qualitek SK-44 saponifier could be used in this process.

Stencil Cleaning
Periodic cleaning of the smt stencil during production is recommended to prevent any paste from being deposited in unwanted areas of the circuit board. Without stencil cleaning, solder balling will increase. We recommend a periodic dry wipe (every 5 to 10 printed circuit boards) with an occasional wet wipe (every 15 to 25 printed circuit boards). When running fine pitch boards, the cleaning may need to become more frequent. The wet wipes should be performed with either alcohol or a stencil cleaner. Qualitek SK-11 stencil cleaner is designed for this purpose. When cleaning the stencil at the end of a job, the cleaning should be more thorough. If you have stencil cleaning equipment Qualitek SK- 44 Stencil Cleaner Saponifier is highly recommended for stencil cleaning purposes.

Disposal
DSP 798LF should be stored in a sealed container and disposed of in accordance with state & local authority requirements.

Packaging

DEK Proflow Cassette		800 gm
6 oz Jar		250-500 gm
6 oz Cartridge		500-700 gm
12 oz Cartridge		1000-1400gm