Archive for the ‘Lead Free Solder’ Category

Lead Free Soder-Wick

Tuesday, August 18th, 2015

Soder-Wick® Lead-Free
1) What exactly is Soder-Wick® Lead-Free SD?
Soder-Wick® Lead-Free SD is a new desoldering braid that has been engineered specifically for optimal removal of lead-free solders, which have a much higher melting point than tin/lead solders. However, it is also effective at removing current tin/lead solders. The SD designation means that the desoldering braid is wound on a static dissipative bobbin to protect the board being reworked from a destructive static discharge.

2) What is the difference between the new Soder-Wick Lead-Free SD and other desoldering
braids like the original Soder-Wick® Rosin and Soder-Wick® No Clean?
The innovative weave of Soder-Wick® Lead-Free SD conducts heat more quickly to the solder joint so more heat energy goes where it is needed to melt the higher melting point, lead-free solders. This shortens the time it takes the solder to liquefy and shortens the overall time required to remove solder when using Soder-Wick® Lead-Free SD. Also, since more of the heat is transferred to the solder joint, Soder-Wick® Lead-Free SD alleviates some of the burden on the soldering iron. The quicker heat transfer means that the operator must also work more quickly to prevent overheating of the solder joint, pad or component. Other wick products do not conduct heat to the solder as quickly and place more emphasis on moderating the heat transfer into the joint. One additional benefit is that some users may find that they can use temperatures for lead-free desoldering similar to conventional tin/lead solders when desoldering with Soder-Wick® Lead-Free. This will reduce oxidation and increase soldering iron tip life
compared with much higher temperature applications.

The innovative weave also makes Soder-Wick® Lead-Free smoother than the current Soder-Wick® Desoldering Braid. This is done
to reduce scratching and marring pads.

Soder-Wick® Lead-Free SD employs a ‘no clean’ flux specifically formulated to tolerate the higher temperatures and poorer wetting capability of currently available lead-free solders.

3)Do I have to use Soder-Wick® Lead-Free to remove lead free solders?
No, Soder Wick® Rosin and Soder-Wick® No Clean will also effectively remove lead-free solder but they are not optimized for leadfree
solder removal. They will require
(a) a soldering iron tip that is slightly larger than the joint and desoldering braid,
(b) possibly higher temperatures, which may shorten soldering tip life and
(c) a higher power soldering iron for faster thermal recovery.Some operators may actually prefer the original Soder-Wick® products and are more comfortable adapting their technique and equipment to lead-free solders, rather than changing to the new Soder-Wick® Lead-Free.

4) Does Soder-Wick® Lead-Free remove lead containing solders effectively?
Yes, Soder-Wick® Lead-Free effectively removes conventional lead containing solders. However, operators accustomed to the original Soder-Wick® may find that the braid heats-up more quickly and must adapt their technique.

Posted in Desoldering, Desoldering Braid, Lead Free Solder | Comments Closed

Lead Free Component Finishes

Tuesday, August 18th, 2015

In the component finish selection avoid lead bearing finishes. The lead in the finish will dissolve into the lead-free solder. This will cause the formation of lead intermetallic phases with differing physical properties (such as expansion/contraction differences) and differing melting points. Work is ongoing to determine the long-term effects of small amounts of lead on high reliability electronics. For many consumer electronic assemblies such as mobile phones and household electronics, where the thermal cycling and condition of use are not extreme the inclusion of lead in component finishes has not demonstrated any negative characteristics to the solder joint integrity. As Japan and Europe progress with lead-free assembly numerous component finishes are already available without lead. It is important to work closely with component suppliers to insure the lead finish is lead-free compatible, the component molding plastic is able to withstand the higher temperatures associated with lead-free soldering and also the component’s reliability will not be jeopardized with the higher exposure temperatures. •Some common finishes include:
◦NiPd
◦NiPdAu
◦SnB
◦Sn
◦SnCu
◦SnAg
◦Au
◦AgPt

◦More finishes are originating from Asia
•PBGA
◦ With SnAgCu, some issues need to be investigated

•Flip Chip
◦ Patented indium alloy compatible with SnAgCu
◦ Might be exempt

•Molded Components
◦Concern about higher processing temperatures, components are available that sustain the higher soldering temperatures.

•Component Process Consideration
◦ Work closely with component suppliers
◦ Determine component lead-free finish availability
◦ Select best solderable finish and component finish shelf life
◦ Select components with compatible molded plastics and the ability to sustain the thermal requirements of the lead- free process
◦ Material handling logistics, segregate lead-free finished components from leaded components, if using both a lead-free and a leaded assembly process
◦ Insure the components and component feeders are identified as containing lead-free finishes.
◦ Train purchasing, receiving and assembly personnel on the handling procedures to avoid confusion between leaded and lead-free components during the transition stage.
◦ Identify the soldered assembly as lead-free to insure the proper rework of the lead-free components in-house and in the field.

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Making Lead-free a Reality

Tuesday, August 18th, 2015

Lead-free fluxes used in solder paste, liquid flux for wave soldering, flux gels and wire solder are available today. These flux systems are designed to enhance the soldering process and are formulated to give excellent solder wetting performance with the added thermal stability of the chemistry, required with lead-free assembly. Traditional fluxes used with tin-lead alloys may not be adequate to circumvent the slower wetting of lead-free alloys and the higher temperatures normally associated with lead-free solders. Flux systems specifically formulated for lead-free soldering will require new activator packages and heat stable gelling and wetting agents to avoid solder defects. Due to the slower wetting and higher surface tension of many lead-free alloys, choosing the right flux for lead-free soldering will prevent the increase of solder defects and greatly assist in maintaining production yields. Typical defects, which can show an increase when transitioning to lead-free assembly are detailed below. These defects can be eliminated with proper flux selection and process control.

• Potential Defect Increase – Lead-free SMT Assembly
◦ Bridging – Paste with poor hot slump behavior
◦ Solder balls – Paste with poor slump properties
◦ Tombstoning – Thermal differences across board
◦ Non-wetting – Excessive preheating or inadequate flux activity
◦ Poor wetting – Poor flux activity or excessive preheating
◦ Solder Voids – Thermal profile too low, or inadequate flux chemistry
◦ Solder beading – Paste with poor hot slump or excessive preheating
◦ Potential Defects Increase – Lead-free Wave Soldering
◦ Bridging – Flux deactivation during preheating or solder contact
◦ Icicling – Flux too low in activity or preheating temperature to high
◦ Solder Balls – Insufficient preheat or flux-solder mask incompatibility
◦ Insufficient Hole-Fill – Flux activity too low, too low solids, or excessive preheat temperature or too low a contact time with molten solder

•Requirements for a Lead-Free Flux:
◦ Low-activation temperature
◦ Adequate shelf life
◦ High activity level
◦ High reliability
◦ Residues benign or easily remove with water if the paste is a water washable type

•Other Considerations for the Lead-free Flux :
◦ Is the paste for dispensing or printing?
◦ Note manufacturers use different types of activators for different alloys
◦ Select flux carefully to balance activation temperature with thermal profile
◦ What is the compatibility of the flux with the alloy selected?
◦ What are the reliability properties (SIR, electro-migration, corrosion)?

Considerations for Lead-free Solderpaste
•Important properties to consider during selection: ◦Solder Balling Test activity
◦ Wetting Test , specific finishes and solder atmosphere (air or nitrogen)
◦ Voiding Potential, lead-free alloys are more prone to solder voids
◦ Tack Life Over Time
◦ Stencil life and abandon time
◦ Cold Slump
◦ Hot Slump tested to higher temperatures 180-185 C ° .
◦ Shelf-life Testing

•Properties to evaluate in-process:
◦Printability
◾Relax/Recovery
◾Print Speed
◾Durability

◦ Component Placement
◾ Drop back for tack

◦ Reflow
◾ Examine solder joint formation on a variety of leads and PWB finishes

• Properties to evaluate after reflow
◦ Thermal Shock
◦ Thermal Cycling
◦ Impact Resistance
◦ Reliability (SIR)

Technical Considerations for Wave Soldering Fluxes Designed for Lead-free Assembly
• Ability to be evenly applicable by spray, wave, or foam applications
• Activator package able to sustain higher preheating temperatures
• Able to be used with a variety of lead-free finishes, bare copper OSP, gold nickel, tin, silver immersion, tin-copper
• Sustained activity, the flux should remain active throughout the contact time with the molten solder, insuring good peel back of the solder
• Low dross potential, the flux must not react excessively with the molten solder as to create large amounts of dross
• The flux must not discolor or char at the higher soldering temperatures associated with lead-free wave soldering
• The flux should not decompose at the higher solder temperatures
• The flux residues must be benign if it is a no-clean flux, and easily washed in hot water if it is a water washable flux type

Technical Considerations for Lead-free Cored Solder Wires
•The flux should not spatter or fume excessively at the slightly higher soldering temperatures associated with lead-free soldering
•The flux should have activator systems designed to solder a variety of lead-free board and component finishes
•The flux must be active enough and remain active enough during tip contact to compensate for the reduced wetting of lead-free alloys
•The flux residues must be benign if it is a no-clean type, or easily removed in hot water if it is a water washable type cored solder
•The residue should not char or darken in color when using slightly higher solder tip temperatures

Source: Kester Solder Co.

Posted in Lead Free Solder, Lead Free Soldering, Process, Solder, Soldering and Rework | Comments Closed

Lead Free Reflow Profile Chart

Monday, August 17th, 2015

Lead-Free-Reflow-Profile-Chart

Posted in Lead Free Solder, Process | Comments Closed

Lead Free RoHS Information

Friday, August 14th, 2015

Which are the exceptions to the RoHS and WEEE directives?
There are a lot of exceptions to the RoHS and WEEE directives. In order to be sure if one or more exceptions apply to the end product or sub product the directive needs to be consulted carefully. In general the military, air and space electronics are exempt. Some Medical devices are also exempt. Alloys with Pb concentration above 85% are equally exempt.

Where can I get up-to-date web information on WEEE and RoHS directives and progress?
Getting up-to-date information is critical to your company’s transition roadmap. A good place is the web and the following website contains updates originating from the TAC (Technical Adaptive Committee) for the RoHS. The website www.dti.gov.uk/sustainability contains copies of the WEEE and RoHS Directives but also the latest minutes of the TAC meetings. Another useful website in reference to the WEEE directive which includes the EU’s perspective is www.europa.eu.int/comm/environment/waste/weee_index.htm.

What are the new IPC-1066 and IPC-1085 Documents and how can they help you in the RoHS-Lead-free transition?
These IPC documents were issued in January 2005. The IPC-1066 is titled “Marking, Symbols and Labels for Identification of Lead-free and Other Reportable Materials in Lead-free Assemblies, Components and Devices” is a document detailing ways to identify components with lead-free finishes, but it can be expanded to board finishes and solder used for assembly. A letter system from e1 to e9 will identify the various lead-free finishes. This document will be used primarily by component manufacturers in the identification and labeling of lead-free components. This document should be used to train procurement, inventory control and production personnel, so as to create an awareness of the component finishes intended to be soldered. The IPC-1065, Material Declaration Handbook details the hundreds of other controlled chemicals restricted in electronic assemblies and also details approved test methods for their detection. It will be useful if a RoHS banned substance must be tested for.

What are the labeling requirements to indicate RoHS product compliance?
The RoHS Directive doesn’t require any specific label to be put on assemblies or box builds. Although some companies have designed their own label and some are using it, by law it is not necessary. Any product entering the European market will be assumed to be RoHS compliant. The same applies to the lead-free logo; it too is not required. Some manufacturers are using their logos to indicate the product is lead-free but this is usually for marketing purposes.

Do I need Material Declarations for my finished product?
A Material Declaration showing compliancy for your product is not required by the EC law. However, if a product entering the European market is intercepted and found to be non-compliant to the RoHS after July 1, 2006, it will be important to demonstrate that a company has done all that is possible in insuring compliancy. Material Declarations or data from each component used in the assembly will then be required. Keeping Material Declarations for each individual item used in a build is important and can show good due diligence has been exercised. A close relationship with suppliers is essential.

What are the main elements required from a Material Declaration Form for my components, boards, wiring, etc.?

The essential elements a Material Declaration must contain are as follows:

Compliancy to European RoHS Directive banned substances,

Free of Polybrominated Biphenyls and Polybrominated Diphenyl ethers flame retardants, can be found in some plastic molding compounds and laminates

Temperature maximum limits for a lead-free soldering process

New Moisture Sensitivity rating for lead-free assembly

The key is to insure banned substances are not present, but also that the parts are lead-free process compatible. Lead-free soldering when using SAC alloys will require hotter thermal profiles. To insure reliability close attention must also be placed on the maximum temperature the part can see but also the impact of moisture.

What is the definition of “lead-free”? Is there an allowable threshold limit?
The EU RoHS directives defines 0.1 wt% (1000ppm) as the threshold for lead per homogeneous material if not intentionally introduced (i.e. each material prior to soldering).This is defined as a limit for each homogenous material, i.e. component lead, lead plating, glass fibres, plastic moulding, solder, pad finish etc. It is NOT defined at 0.1% by mass of the finished product, or circuit board.

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Pin Holes: Pin holes often appear on the surface of solder joints. How are they formed?

Friday, August 14th, 2015

Pin holes are formed as a result of moisture entrapment. All that is required is a tiny amount of moisture. When the solder comes in contact with the through-hole, component lead, wire or whatever is being soldered, the water boils and it forms a gas bubble that will either escape or be trapped as the solder solidifies

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