Bow 3451 Solder Paste For Difficult Solderable Surfaces

BOW ELECTRONIC SOLDER
TECHNICAL BULLETIN
BOW #3451
SOLDER PASTE FOR DIFFICULT TO SOLDER SURFACES

Description :

BOW 3451 is a ready to use homogenous mixture consisting of metal powders, binders, solvents, fluxes and thixotropic agents, This paste has excellent wetting capability and is ideal for applications where difficult to solder surfaces have to be joined. Variations in pad and component solderability is tolerated without a negative effect yields.

Typical Properties:

Metal Powder:

Alloy
Particle Size:
Shape: Melting Point:
% Metal:

63Sn/37Pb fully alloyed
25-75µm
spherical
183°C
89-91%

Organic Vehicle:

If the paste is properly stored it's composition prevents crusting and ensures the following rheological properties.

excellent printability

stable viscosity

Flux Activity:

According to Federal Specifications QQ-S-571-E: RMA

Cleaning Of Flux Residues:

The cleaning can be done with:

Freon

Terpene

Aqueous cleaners using saponifier; Saponifier concentration: apporx. 9%.
Water temperature: 60-65°C (140-150°F)

For Optimum results:

Clean circuits immediately after reflow, while still warm.

High pressure spray and/or ultrasonic can improve cleaning under large, tightly
spaced, or low clearance components.

Recommended Processing Guidlines:

Ensure that the paste has reached room temperature before opening to prevent condensation. Stir well prior to use. Print through stencil.

Printing Data: (Stencil)

Paste viscosity: 80 - 1000 Pas (Brookfield RV, TF spindle 5 RPM @ 25°C ) Thickness: typical 0.008" = 200µm
Min pitch: 0.02" = 500µm
Min pad width: 0.01" = 250µm
Clean wet paste with isopropanol or similar solvents.
If the printing interval exceeds 1 hour, remove the paste from the stencil.
The printed solder paste remains tacky for up to 24 hours to allow device insertion. The exact time depends on the environmental conditions.
If the printed circuits will be stored prior to reflow for more than 24 hours, it is advisable to store them in tightly closed areas. This is especially important if the relative humidity exceeds 65%. Humidity should be kept below 65% to avoid solder balling and dewetting.
Reflow paste at 205-230°C. For optimum results the temperature should be maintained for a min of 30 seconds at >180°C, and heating should be uniform across the substrate and components.
Reflow can be accomplished with nearly any known process.

Storage:

Maximum 6 months under the following conditions. Store the solder paste in tightly sealed jars at room temperature. DO NOT REFRIGERATE. Avoid exposure to sunlight and high humidity.