Flux Types
Expert reports

Flux Types

In accordance with IPC-J-STD-004

Flux Types in accordance with IPC-J-STD-004

IPC

IPC is a global trade association dedicated to the competitive excellence and fi nancial success of its member companies which represent all facets of the electronics interconnect industry, including design, printed circuit board manufacturing and electronics assembly.

As a member-driven organization and leading source for industry standards, training, market research and public policy advocacy, IPC supports programs to meet the needs of an estimated $1.5 trillion global electronics industry.

right arrow Founded in 1957 as the Institute of Printed Circuits with 6 Member Companies

right arrow Strong Foundation as Technical Organization Dedicated to Meeting Industry Needs

right arrow Focus on Design, PCB Manufacturing and Electronics Assembly.

 

Benefi ts of IPC Standards

The benefi ts of IPC Standards is that they are used and recognized worldwide, and the most important standards are available in almost all the languages. The IPC Standards cover the complete process from the Design, Bare Board Manufacturing, Assembly and Box Building including Fiber Optics.

 

In the following Spec Tree you can see an overview of the most used IPC Standards:

IPC specifications Tree
 

IPC Classification

Accept and/or reject decisions shall be based on applicable documentation such as contracts, drawings, specifications, standards and reference documents.

 

IPC defines three product classes, which are as follows:

class 1 - General Electronic Products Includes products suitable for applications where the major requirement is function of the completed assembly.

Class 2 - Dedicated Service Electronic Products Includes products where continued performance and extended life is required, and for which uninterrupted service is desired but not critical. Typically the end-use environment would not cause failures.

Class 3 - High Performance/Harsh Environment Electronic Products Includes products where continued high performance or performance-on-demand is critical, equipment downtime cannot be tolerated, end-use environment may be uncommonly harsh, and the equipment must function when required, such as life support or other critical systems.

The customer (user) has the ultimate responsibility for identifying the class to which the assembly is evaluated. If the user and manufacturer do not establish and document the acceptance class, the manu- facturer may do so.

 

IPC J-STD-004B Requirements for Soldering Fluxes

IPC J-STD-004B December 2008 and J-STD-004B-Amendment-1 November 2011

According to the J-STD-001 Requirements for Soldered Electrical and Electronic Assemblies it is mandatory that the flux should fulfil the requirements of the J-STD-004.

The J-STD-004 is a Flux classification document, all fluxes can be subdivided into 1 to 24 Flux Classifications.

The fluxes shall be classified according to the materials of composition and flux type, the flux designators identify both composition and type of fluxes.

 

24 Flux Certificates

Flux Materials Flux Activity Flux Designator
Rosin (RO) Low (0%) L0 ROL0
Low (<0,5%) L1 ROL1
Moderate (0%) M0 ROM0
Moderate (0,5%-2,0%) M1 ROM1
High (0%) H0 ROH0
High (<2,0%) H1 ROH1
Resin (RE) Low (0%) L0 REL0
Low (<0,5%) L1 REL1
Moderate (0%) REM0
Moderate (0,5%-2,0%) M1 REM1
High (0%) H0 REH0
High (<2,0%) H1 REH1
Organic (OR) Low (0%) L0 ORL0
Low (<0,5%) L1 ORL1
Moderate (0%) ORM0
Moderate (0,5%-2,0%) M1 ORM1
High (0%) H0 ORH0
High (<2,0%) H1 ORH1
Inorganic (IN) Low (0%) L0 INL0
Low (<0,5%) L1 INL1
Moderate (0%) INM0
Moderate (0,5%-2,0%) M1 INM1
High (0%) H0 INH0
High (<2,0%) H1 INH1
 

Rosin- based Flux (RO – Type):

right arrow Rosin (Colophony) is general extracted from pineapple tree juice.

right arrow Solid at room temperature

right arrow Chemically inactive at room temperature

right arrow Isolating at room temperature

right arrow Rosin melts at approx. 72°C

right arrow Organic acids become active at approx. 108°C

right arrow His optimum function is at approx. 262°C

right arrow At temperatures above 346 oC this flux becomes inactive and polymerises, which causes problems with cleaning the residue

 
Rosin (RO)
right arrow Natural Rosin (Colophony)
right arrow The IPC-J-STD-004
standard designates this flux as – RO

Resin- based Flux (RE – Type):

right arrow Resin is a common used technical term with a double meaning.

right arrow It encloses a variety of natural and synthetically resinous products.

 
Rosin (RE)
right arrow The IPC-J-STD-004
standard designates this flux as - RE

Water soluble (Organic Acid) Flux:

right arrow Original build up by organic acids different from Rosin or Resin.

right arrow Organic Flux (OR) often called OA Flux

right arrow Common on market as WSF’s (Water Soluble Flux)

right arrow Many 'low solids fluxes' fall into the OR category

right arrow As the name already tells us, this flux is build up with water soluble chemicals.

right arrow After the soldering operation the flux residue can be easily cleaned with tap water.

right arrow This flux is very popular, because it is free of anti-pollution tax, as paid by other flux types.

 
Rosin (RE)
right arrow The IPC-J-STD-004
standard designates this flux as – RE
 

Inorganic (IN) Flux:

Flux with inorganic salts are commonly not used for soldering PCBs because the extreme corrosive residue, but are sometimes used for soldering non-electric products. (i.e. lightning rod materials)

Inorganic (IN)
right arrow The IPC-J-STD-004
standard designates this flux as – IN
 

J-STD-004 Flux Classification

This means: the degree of effectiveness of the Flux.

The worse the solder ability of the PCB surface is, the higher the flux activity should be to create a good wetting.

Not activated or activated (L = low, M = moderate, H = high)

If you hear this you should logically always choose the most active flux to create a good wetting in all situations. Unfortunately it is not so easy! If you use high activated flux, you have more problems with oxidation of the flux residue.

The IPC-J-STD-004 Classifications

Flux synthesis
right arrow ROsin
right arrow REsin
right arrow ORganic
right arrow INorganic
value 4x3
Flux activity
right arrow Low
right arrow Moderate
right arrow High
value 12x2
Halogen or
Halide free
right arrow L0
right arrow L1
 

Flux types (activity/Residue)

Table 3.1 Test Requirements for Flux Type Classification

Flux Type Qualitative Copper Mirror2 Qualitative Halide(Optional) Quantitative Halide Qualitative Corrosion Test Conditions for Passing 100 MQ SIR Requirements2 Conditions for Passing ECM Requirements2
Silver Chromate(Cl, Br) Spot Test(F) ((Cl, Br, F)(by weight)
L0 No evidence of mirror breakthrough Pass3 Pass3 0.0% 1 No evidence of corrosion Uncleaned6,7 Uncleaned6,7
L1 Pass3 Pass3 <0.5%
M0 Breakthrough in less than 50% of test area Pass3 Pass3 0.0% 1 Minor corrosion acceptable Cleaned7 or Uncleaned8 Cleaned7 or Uncleaned8
M1 Fail4 Fail4 0.5% to 2.0%
H0 Breakthrough in less than 50% of test area Pass3 Pass3 0.0% 1 Major corrosion acceptable Cleaned Cleaned
H1 Fail4 Fail4 >2.0%

Flux activity L: Copper Mirror Test

right arrow 50 nm thick layer of Copper on a glass plate.

right arrow Put one drop of flux on the mirror.

right arrow Inspect the effect of the Copper layer after 24 hours

right arrow The flux shall be classified as type L only if there is no complete removal of the copper film.

 

If there is any removal of the copper film, as evidenced by the background showing through the glass, then the flux shall not be classified as type L.

Flux activity M: Copper Mirror Test

right arrow 50 nm thick layer of Copper on a glass plate.

right arrow Put one drop of flux on the mirror.

right arrow Inspect the effect of the Copper layer after 24 hours.

If there is complete removal of the copper only around the perimeter of the drop (less than 50% breakthrough), then the flux shall be classified as type M.

Flux activity H: Copper Mirror Test

right arrow 50 nm thick layer of Copper on a glass plate.

right arrow Put one drop of flux on the mirror.

right arrow Inspect the effect of the Copper layer after 24 hours.

If the copper film is completely removed (greater than 50% breakthrough), then the flux shall be classified as type H.

 

24 Flux Certificates

Flux Materials Flux Activity Flux Designator
Rosin (RO) Low (0%) L0 ROL0
Low (<0,5%) L1 ROL1
Moderate (0%) M0 ROM0
Moderate (0,5%-2,0%) M1 ROM1
High (0%) H0 ROH0
High (<2,0%) H1 ROH1
Resin (RE) Low (0%) L0 REL0
Low (<0,5%) L1 REL1
Moderate (0%) REM0
Moderate (0,5%-2,0%) M1 REM1
High (0%) H0 REH0
High (<2,0%) H1 REH1
Organic (OR) Low (0%) L0 ORL0
Low (<0,5%) L1 ORL1
Moderate (0%) ORM0
Moderate (0,5%-2,0%) M1 ORM1
High (0%) H0 ORH0
High (<2,0%) H1 ORH1
Inorganic (IN) Low (0%) L0 INL0
Low (<0,5%) L1 INL1
Moderate (0%) INM0
Moderate (0,5%-2,0%) M1 INM1
High (0%) H0 INH0
High (<2,0%) H1 INH1

Flux types (activity):

right arrow L0-type flux: all type R, some RMA, some Low Solids ,,No Clean“.

right arrow L1-type flux: most RMA, some RA

right arrow M0-type flux: some RA, some Low Solid „No clean“

right arrow M1-type flux: most RA, some RSA

right arrow H0-type flux: some water soluble

right arrow H1-type flux: some RSA, most water soluble and synthetic activated

 
arrow new
Flux Activity Flux Types
L0 All R
Same RMA
Same Low soids, No-Clean
L1 Most RMA
Same RA
M0 Same RA
Same Low solids, No-Clean
M1 Most RA
Same RSA
H0 Same water soluble
H1 Same RSA
Most water soluble
Most synthetic activated
arrow old
 
Activators blue arrow Speed up
 
Vehicles blue arrow Carriers
 
Solvent blue arrow Solve
 
Special Additives blue arrow Special properties
 

Activators

Activators are chemicals which are added in small portions on to the flux to remove oxides which are located on the base material.

 

When an activator functions, it is a corrosive action:

Low activated flux = corrosive at room temperature
High activated flux = corrosive at solder temperature

Flux activity systems are build up with:

right arrow Acids,

right arrow Halides,

right arrow or a combination of both.

 

Flux Activators can be:

right arrow Halogens,

right arrow Organic/Inorganic acids

right arrow Synthetic activators

The most characteristically chemical property of halogens is the possibility to oxidize.

 

Fluor has the property to oxidize.

Almost all elements of group 7 of the periodic system of elements (Fluorine, Chlorine, Bromine and Iodine) react directly with metal, with decrease reactivity below in the group.
The reaction should be activated by heat or UV-light.

Halogenides are halogen oxides.

 

Halogens are group VII in the periodic system of elements:

right arrow Fluorine (F)

right arrow Chlorine (Cl)

right arrow Bromine (Br)

right arrow Iodine (I)

right arrow Astatine (At) (Radioactive and unstable)

Halogen:

The presence of halogen in flux is indicated with:

right arrow 0 No halogen (oxides) in Flux (residue).

right arrow 1 Halogen (oxides) in Flux (residue).

 

Minimum percentage halogen part per weight of solid constituents in the flux:

right arrow L0, M0, H0 = 0,0%

 

Halogen free activators:

right arrow Chlorine compositions: Ammonium Chlorines & Hydro Chlorines

right arrow Acids: Phosphor Acids & Carboxyl Acids

right arrow Salts

 

Maximum percentage halogens part per weight of solid constituents in the flux:

right arrow L1, <0,5%

right arrow M1, 0,5% to 2,0%

right arrow H1, > 2,0%

 

The carrier is build up with:

right arrow a solid substance or

right arrow a non-volatile liquid or

right arrow a combination of both.

 

Three functions of a carrier:

1. A carrier is used as a dissolver of materials which are formed during the reaction between oxides and activators on high temperatures.

2. It takes care, that no air inclusion can occur in the solder connection or on the soldering surface. It functions as a blanket.

3. It takes care for a good heat transfer between the solder and the surface.

 

Solvents:

The solvent in the liquid flux (i.e. in a wave soldering machine), has a primary function to drive off the activators and the vehicles to the surface of the PCB.

During the preheat stage the solvent will evaporate. During soldering only the activators and the carriers will remain.

Special additives

These additives are added to the flux with deviations and for special functions:

right arrow Stabilizers – for thermal stability

right arrow Inhibitors – to minimize oxidation

right arrow Dyes – colourize the flux

 

Flux types (activity/Residue):

Required SIR Test. The SIR requirements for fluxes shall be determined in accordance with IPC-TM- 650, Test Method 2.6.3.3.

All SIR measurements on all test patterns shall exceed the 100 MΏ requirements when measured at 96 and 168 hours.

Both the initial insulation resistance (IR Initial, measurement taken after the 96 hour stabilization period) and the final insulation resistance.

(IR Final, measurement taken after exposure to bias for 500 hours) values shall be reported according to the test method.

 
Flux Type Qualitative Copper Mirror2 Qualitative Halide (Optional) Quantitative Halide Qualitative Corrosion Test Conditions for Passing 100 MQ SIR Requirements2 Conditions for Passing ECM Requirements2
Silver Chromate(Cl, Br) Spot Test(F) (Cl, Br, F) (by weight)
L0 No evidence of mirror breakthrough Pass3 Pass3 0.0% 1 No evidence of corrosion Uncleaned6,7 Uncleaned6,7
L1 Pass3 Pass3 <0.5%
M0 Breakthrough in less than 50% of test area Pass3 Pass3 0.0% 1 Minor corrosion acceptable Cleaned7 or Uncleaned8 Cleaned7 or Uncleaned8
M1 Fail4 Fail4 0.5% bis 2.0%
H0 Breakthrough in less than 50% of test area Pass3 Pass3 0.0% 1 Major corrosion acceptable Cleaned Cleaned
H1 Fail4 Fail4 >2.0%
 

The criteria for passing the ECM test (Electro Chemical Migration Test) are:

 

1. IR Final3 (IR Initial)/10, that is the average insulation resistance shall not degrade by more than one decade as a result of the applied bias.

2. No evidence of electrochemical migration (dendritic filament growth) that reduces the conductor spacing by more than 20%.

3. No corrosion of the conductors; minor discoloration of one polarity of the comb pattern conductors is acceptable.

Flux Type Qualitative Copper Mirror2 Qualitative Halide (Optional) Quantitative Halide Qualitative Corrosion Test Conditions for Passing 100 MQ SIR Requirements2 Conditions for Passing ECM Requirements2
Silver Chromate (Cl, Br) Spot Test(F) (Cl, Br, F) (by weight)
L0 No evidence of mirror breakthrough Pass3 Pass3 0.0% 1 No evidence of corrosion Uncleaned6,7 Uncleaned6,7
L1 Pass3 Pass3 <0.5%
M0 Breakthrough in less than 50% of test area Pass3 Pass3 0.0% 1 Minor corrosion acceptable Cleaned7 or Uncleaned8 Cleaned7 or Uncleaned8
M1 Fail4 Fail4 0.5% bis 2.0%
H0 Breakthrough in less than 50% of test area Pass3 Pass3 0.0% 1 Major corrosion acceptable Cleaned Cleaned
H1 Fail4 Fail4 >2.0%

Labelling

The manufacturer must label each container of solder flux (J-STD-004) with following information:

right arrow The manufacturer’s name and address.

right arrow Part number.

right arrow Complies with J-STD-004.

right arrow Designation of the flux.

right arrow The batch number.

right arrow The net mass of the flux.

right arrow The date of manufacturing and shelf life.

right arrow Health, safety and environmental markings.

 

Source: J-STD-004 & PIEK’s Flux Presentation

 
 

Rob Walls MIT/CID+
Managing Director

 

PIEK International Education Centre BV, Netherlands