No-Clean Flux Low-Solids High Reliability

ALPHA® SLS 65
No Clean Flux

An active, low solid, no-clean flux specifically developed to eliminate
the tendency for solder balling and solder bridging over a wide variety of solder masks.

Product Overview

ALPHA SLS 65 is an active, low solid, no-clean flux. It is formulated with a proprietary mixture of organic activators. Several proprietary additives are formulated into ALPHA SLS 65, which act to reduce the surface tension between the solder resist and the solder, thereby dramatically reducing the tendency of solder ball generation. The formulation of ALPHA SLS 65 is also designed to be more thermally stable, thereby reducing the occurrence of solder bridging.

ALPHA SLS 65 is specifically developed to eliminate the tendency for solder balling and solder bridging – two defects that are normally associated with the use of the chip wave. Of all low solids (<4% solids), no-clean fluxes, ALPHA SLS 65 exhibits the lowest tendency for solder ball generation over a wide variety of solder masks.

ALPHA® SLS 65

Key Features

Liquid Flux
  • Lowest Solder Bridging Thermally stable activators provide the lowest solder bridging in a low-solids, no-clean flux.
  • Lowest Solder Ball Frequency Reduces the surface tension between solder and resist to provide the lowest solder ball frequency of any low solids, no-clean flux.
  • Pin Testing Compatible Very low level of non-tacky residue to reduce interference with pin testing and exhibit no visible residue.
  • Cost Effective Cleaning is not required which reduces operating costs.
  • Bellcore Compliant Bellcore Compliant for long-term electrical reliability.

Ideal for Sensitive Board Designs

ALPHA SLS 65 should be considered for use by any assembler who has board designs that are sensitive to solder bridging.

It is highly recommended for processes that perform pin testing or whose specification requires an extremely low frequency of solder balls.

PCB Assembly
View Detailed Technical Specifications

APPLICATION GUIDELINES

Preparation: In order to maintain consistent soldering performance and electrical reliability, it is important to begin the process with circuit boards and components that meet established requirements for solderability and ionic cleanliness. A common specification for the ionic cleanliness of incoming boards and components is 0.77 μg/cm² (5 μg/in²) maximum, as measured by an Omegameter with heated solution. Boards should always be held at the edges. The use of clean, lint-free gloves is also recommended. When switching from one flux to another, the use of a new foam stone is recommended (for foam fluxing). Conveyors, fingers, and pallets should be cleaned.

Flux Application: ALPHA SLS 65 is formulated to be applied by foam, wave, or spray methods. When foam fluxing, the foam fluxer should be supplied with compressed air which is free of oil and water. Keep the flux tank full at all times. The flux level should be maintained 25 to 40 mm (1 to 1½”) above the top of the stone. Adjust the air pressure to produce the optimum foam height with a fine, uniform foam head. When using the foam or wave method of application, an air knife is recommended after the fluxing operation.

Operating ParameterRecommendation
Amount of flux to be appliedFoam, Wave: 155 to 232 µg/cm² of solids
Spray: 140 to 250 µg/cm² of solids
When foam fluxing:
Foam Stone Pore Size
Distance that top of stone is submerged below flux
Foam Fluxer Chimney Opening
20 to 50 μm
25 to 38 mm

10 to 13 mm
When foam fluxing, use an air knife:
Air knife hole diameter:
Distance between holes
Distance from Fluxer to Air knife
Air knife angle back toward fluxer from perpendicular
1 to 1.5 mm
4 to 5 mm
10 to 15 cm
3 to 5°
Topside Preheat Temperature100 to 120 °C
Bottom side Preheat Temperatureabout 35 °C higher than topside
Maximum ramp rate of topside temperature2 °C/second maximum
Conveyor angle5 to 8 °C (6 °C most common)
Conveyor speed1.00 to 2.00 meters/minute
Contact time in the solder
(Includes chip wave and primary wave)		1.5 to 3.5 seconds (2½ to 3 seconds most common for 63/37 Sn-PB
2 to 7 seconds (2½ to 5 seconds most common for Lead-free)
Solder pot temperature235 to 260 °C (460 to 500 °F) for 63/37 Sn-Pb
255 to 270 °C (491 to 518 °F) for Lead-free

Flux Solids Control & Residue Removal

Flux Solids Control: If foam, wave, or rotary drums spray fluxing, the flux solids will need to be controlled via thinner addition to replace evaporative losses of the flux solvent. Monitoring and controlling the acid number is recommended for maintaining the solids content. The acid number should be controlled between 17 and 19. When operating the foam fluxer continuously, the acid number should be checked every two to four hours.

Residue Removal: ALPHA SLS 65 is a no-clean flux and the residues are designed to be left on the board. However, if desired, ALPHA SLS 65 residues can be removed with ALPHA 2110 Saponifier.

Touch-Up/Rework: Use of ALPHA Cleanline Write Flux Applicator with ALPHA NR205 flux, and ALPHA Telecore Plus cored solder wire is recommended for hand soldering applications.

TECHNICAL DATA

ItemTypical ValuesItemTypical Values
AppearanceClear, colorless liquidFlash Point (T.C.C.)12 °C (53 °F)
Solids Content, wt/wt2.3%Recommended ThinnerALPHA 425
Specific Gravity @ (77±1 °F) (25 °C ±1.8 °C)0.801 ± 0.003Bellcore TR-NWT-000078, Issue 3 compliantYes
Acid Number (mg KOH/g)18 +/-1IPC J-STD-004 DesignationORL0
pH (5% aqueous solution)3.36 +/- 0.30Shelf Life (From date of mfg.)360 days

CORROSION & ELECTRICAL TESTING

Corrosion Test

TestRequirement for ROL0Results
Silver Chromate Paper
IPC-TM 650 Test Method 2.3.33		No detection of halidePASS
Copper Mirror Test
IPC-TM 650 Test Method 2.3.32		No complete removal of copperPASS
Copper Corrosion Test
IPC-TM650 Test Method 2.6.15		No evidence of corrosionPASS

IPC-J-STD-004A Surface Insulation Resistance

TestConditionsRequirementsResults
“Comb down” – Uncleaned85 °C/85% RH, 7 days> 1.0 x 10⁸2.1 x 10⁹
“Comb up” – Uncleaned85 °C/85% RH, 7 days> 1.0 x 10⁸1.5 x 10⁹
Control Board85 °C/85% RH, 7 days> 1.0 x 10⁹1.1 x 10¹⁰

Bellcore Surface Insulation Resistance

Test ConditionRequirementsResults
Bellcore “Comb-Down” – uncleaned> 1.0 x 10¹¹4.5 x 10¹¹
Bellcore “Comb-Up” – Uncleaned> 1.0 x 10¹¹1.4 x 10¹¹
Bellcore Control Board> 2.0 x 10¹¹9.3 x 10¹¹

Bellcore Electromigration

TestSIR (Initial)SIR (Final)RequirementResult
"Comb-Up" Uncleaned6.8 x 10⁹ Ω2.1 x 10⁹ ΩSIR(Initial) / SIR(Final) < 10Pass
"Comb-Down" Uncleaned1.0 x 10¹¹ Ω3.2 x 10¹¹ ΩSIR(Initial) / SIR(Final) < 10Pass

Product Documentation

ALPHA® SLS 65 Flux TDS

English