Supplementary Quotations"As recycling electrical and electronic devices is good for the environment, the RoHS directive is not applicable to second-hand equipment. Repairing and even upgrading the devices marketed before 1st July 2006 may also be realized with non-RoHS compatible components, insofar as this product is not marketed as new. Products marketed as new products from 1st July 2006 must be repaired with RoHS compatible components."[1]
"Interestingly, products using leaded solder can still be sold, but only if they were introduced before July 1st 2006. In practice, though, this is only a short-term arrangement and will generally apply to only a few products, mainly from small manufacturers. However, the situation gets a little more involved when it comes to spare parts and repairs. Fortunately, the RoHS directive recognises that non-compliant components will be required to maintain 'legacy' equipment, and so permits their production and sale indefinitely — but whether the manufacturers will feel the market is sufficient to warrant their production is another matter!
"Related to all this is the fact that mixing leaded and lead-free solders is really not a good idea at all. So service centres will need to identify which kind of solder is employed in a product and use something compatible when making repairs. Reliability could be adversely affected by lead contamination of a lead-free circuit board, or by mixing lead-free and lead solders on an 'antique' PCB."[2]
"When the lead spacing of a capacitor does not match the hole spacing on your PCB, the capacitor should have its leads formed to avoid exposing the capacitor to excessive mechanical stress.
"The maximum amount of lead stress should be limited to 1.0 Kg in the vertical direction and 0.5Kg in the horizontal direction.
"You should also avoid bending the leads of your capacitor right next to the capacitor body itself - the internal connections from a capacitor’s leads to its actual capacitive material are delicate and can easily be damaged. Leave at least a millimeter or two between the capacitor body and the first bend in your leads to avoid breaking those delicate connections."[3]
"Aluminum electrolytic capacitors are polarized. Make sure that no reverse voltage or AC voltage is applied to the capacitors. Please use bi-polar capacitors for a circuit that can possibly see reversed polarity.
Note: Even bi-polar capacitors can not be used for AC voltage application.
"There are non-halogen types of flux that do not contain ionic halides, but contain many non-ionic halides. When these non-ionic halides infiltrate the capacitor, they cause a chemical reaction that is just as harmful as the use of cleaning agents. Use soldering flux that dose not contain non-ionic halides.
"1) Do not use any fixing or coating materials, which contain halide substance.
2) Remove flux and any contamination, which remains in the gap between the end seal and PC board.
3) Please dry the cleaning agent on the PC board before using fixing or coating materials.
4) Please do not apply any material all around the end seal when using fixing or coating materials.
"(1) Take either of the following methods in disposing of capacitors.
- Make a hole in the capacitor body or crush capacitors and incinerate them.
- If incineration is not applicable, hand them over to a waste disposal agent and have them buried in a landfill.
"(2) When removing a capacitor from the circuit board or when disposing of capacitor please ensure that the capacitor is properly discharged."[4]
"Parts which dissipate heat in quantities of 1 Watt or greater, or in quantities sufficient to damage the laminate shall be mounted with sufficient standoff [ > 1.5mm (0.060 in.) ] and shall be mechanically restrained.
"Components weighing in excess of 7 g (0.25 oz.) total, or 3.5 gm (0.12 oz.) per lead, shall be mechanically secured to the mounting surface by at least 4 evenly spaced bonds, when no other mechancial support is used.
"Parts having conductive cases, which are mounted over printed conductors or which are in close proximity to other conductive materials shall be separated by insulation of suitable thickness, or shall have an insulating jacket/sleeve.
"Exposed ends of leads on straight-through termination shall not be cause for rejection if the PWA is to be conformally coated.
"Parts shall be mounted in such a manner that, at a minimum, the markings are visible in the following order of precedence: polarity, traceability/lot code (if applicable), part value, part number/type.
"Contamination is a reliability concern.
"Parts with damaged seals shall not be used.
"Dewetting is caused when molten solder coats a surface and then recedes, leaving irregulary-shaped solder deposits separated by areas covered by a thin solder film.
"A disturbed solder joint is characterized by the appearance that there was motion between the metals being joined while the molten solder was solidifying.
"Parts shall not be mounted such that they obstruct solder flow to the component-side termination area (pad) or prevent cleaning and inspection.
"Leads shall be cut per engineering documentation and by methods, which do not impart stress to the lead seal or internal terminations.
"Parts shall be mounted parallel to the laminate surface, right side up and aligned to the lands within design and engineering specifications.
"The use of parts with nicks in the component body or termination area is prohibited.
"Poor wetting is an indicator of poor solderability, improper flux or contamination."[5]
"Flow (wicking) of solder along the conductor is permitted. Solder shall not make presence of the individual wire strands indistinguishable.
"Tin the iron tip, while the connection is cooling at room temperature. A small amount of solder should remain on the tip.
"Minimum steps to protect ESD-sensitive devices are:
- Always work at a grounded workstation
- Use only ESD-approved materials
- Handle ESD-sensitive devices only at static-safe workstations
- Always use a conductive wrist strap before handling ESD-sensitive devices
- Use an ESD bag or container to store or carry parts in.
"Hot tinning of solid conductors and part leads should not extend closer than 0.5mm (0.020 inch) to part bodies, end seals, or insulation unless the part configuration and mounting configuration dictate it.
"Cut the lead.
- Straight-through leads may be bent up to 30 degrees from a vertical plane to retain parts during the soldering operation.
- Part leads terminated straight through the PWB shall extend a minimum of 0.51 mm (0.020 in.) and a maximum of 2.29 mm (0.090 in.).
"Position the soldering iron tip so as to touch both the lead and the printed wiring pad at the same time.
"Apply solder to the junction where the iron and lead meet in order to produce a thermal (solder) bridge.
"Touch the solder to the end of the cut lead to cover the exposed copper.
"Add solder as needed to complete the soldered connection.
"Remove the solder; remove the iron.
"The end of the part body must be mounted with at least 0.51 mm (0.020 in.) to a maximum of 1.27 mm (0.050 in.) clearance above the PWB surface. The end of the part is defined to include any extensions such as coating meniscus, solder seal, or weld bead.
"Inspect the solder joints under 4 X to 10 X magnification to the specified requirements.
- Free of flux residue and other contaminants.
- The solder shall wet all elements of the connection.
- The solder shall fillet between connection elements over the complete periphery of the connection."[6]
"Adhesive materials, when used,
shall not⁴ preclude the formation of an acceptable solder connection. Adhesive materials extending from under SMT components
shall not⁵ be visible in the termination area.
"When hand soldering a component identified as heat sensitive, a thermal shunt or heat sink
shall² be attached to the device lead between the area to be soldered and the component body to minimize component heating.
"Wetting cannot always be judged by surface appearance. The wide range of solder alloys in use may exhibit from low or near zero degree contact angles to nearly 90° contact angles as typical. The acceptable solder connection
shall¹ indicate evidence of wetting and adherence where the solder blends to the soldered surface.
"Lead-free and tin-lead connections may exhibit similar appearances but lead free alloys are more likely to have surface roughness (grainy or dull) or different wetting contact angles.
"The lead and wire ends should not extend beyond the terminal more than one (1) lead diameter.
"Part and component leads should be preformed to the final configuration excluding the final clinch or retention bend before assembly or installation. The lead forming process
shall not⁵ damage lead seals, welds, or connections internal to components."[7]
"At soldering iron temperature, solder will stick to oxides and contaminants to produce a visually acceptable connection. However, the connection lacks an intermetallic bond and the high temperature degrades bonds inside components. The altered bonds change electrical values and shorten component life. In just a few seconds of improper application, a soldering iron can shorten the life expectancy of components by decades.
"The arrival of solid-state components meant that, for the first time, solder was applied directly to the component rather than wires and sockets. In other words, the components were subjected to the soldering heat. And this had profound reliability consequences because heat degraded the component electrical properties.
"To prevent heat damage during soldering, metal clamps were attached to leads next to the component body. Heat flowed from the soldering iron towards the component but was absorbed by the clamps before it could reach the component body. The clamps were called “heat sinks” and they provided absolute protection against heat damage."[8]
"No-clean solder paste generally doesn’t require cleaning.
"In reality, no-clean solder paste leaves behind flux with low residue. The reflow process leaves trace amounts of resinous residue, noncorrosive in nature. Present on or around solder joints, the residue can vary in color from amber to transparent. The residue left on the board after reflow depends directly on the solid content in the solder paste, mainly made up of activators, gelling agents, and resins.
"The primary intention for removing the no-clean flux and its residue from the board surface is to prevent interference with signal transmission and malfunction in circuit functioning.
"Numerous no-clean flux removers are available in the market, and their strengths vary."[9]
"Activated rosin fluxes contain small quantities (0.2% to 5%) of organic activating agents. The purpose of these activators is to catalyze the rosin copper oxide reaction so that a better soldering job can be obtained. The catalytic agents do not enter into the reaction and do not cause subsequent corrosion. However, the presence of these activators does impel the rosin (abietic acid) to combine with the copper oxide to form the green copper abietate compound. Copper abietate is not conductive and forms a green insulating coating on copper. Usually the dark rosin residue conceals this normal formation of green copper abietate."[10]
"Electrolytic capacitors are able to survive some transient current abuse, typically more than their metallized film counterparts. As a rule of thumb, for brief ripple current excursions such as several seconds of 2 to 4 times the rated load ripple current, the thermal mass of the capacitor winding will absorb a lot of the extra energy dissipation of such an event.
"For aluminum electrolytic capacitors, dielectric absorption will allow up to 10% recovery of a previously applied voltage. Thus with high-voltage aluminum electrolytic capacitors rebound voltages of 40 to 50 V are possible. While such voltages are not usually a shock hazard, they can certainly cause sparking and even arc damage during installation.
"During charging the voltage on each capacitor connected in series is proportional to the inverse of the actual capacitance, but upon reaching the applied voltage, the steady-state DC voltage that each capacitor approaches no longer depends upon its capacitance at all, instead shifting to follow the inverse of the capacitor’s leakage current.
"Ripple current is the AC current flowing through the capacitor. It’s called ripple current because the associated AC voltage rides on the capacitor’s DC bias voltage as a ripple rides on the surface of water. The ripple current heats the capacitor, and the maximum permitted ripple current is set by how much heat rise can be permitted while still meeting the capacitor’s load life specification. Too much temperature rise will cause the capacitor to exceed its maximum permitted core temperature and fail; even operation close to the maximum permitted core temperature dramatically shortens expected life.
"Don’t exceed the maximum storage temperature while preheating the capacitors [...] Don’t contact insulating sleeve or other plastic parts with a soldering iron or molten solder.
"When gluing, don’t apply glue to the full capacitor circumference, and don’t cover the capacitors’ pressure-relief vent with potting or glue.
"In the case of electrolyte contact to skin, immediately rinse the exposed area with soap and water. If electrolyte contacts eyes, flush for 10 minutes with running water and seek medical attention. If vapors are present, ventilate the room."[11]
"1) A capacitor with more than a certain case size has the pressure relief vent functioning to escape abnormal gas pressure increase.
If gas expels from a venting capacitor, disconnect the power supply of the device or unplug the power supply cord. If not disconnecting the power supply, the device circuit may be damaged due to the short circuit failure of the capacitor or short-circuited with the liquid that the gas was condensed to. It may cause secondary damages such as device burnout in the worst case scenario.
The gas that comes out of the open vent is vaporized electrolyte, not smoke.
2) The gas expelled from a venting capacitor is more than 100°C. Never expose your face to the capacitor. If your eyes are exposed to the gas or you inhale it, immediately flush your eyes and/or gargle with water. If the electrolyte comes in contact with the skin, wash with soap and water."[12]
References[1] Willems, Geert.
The RoHS Directive: An Answer to Your Questions. Sirris.
https://www.cedm.be/system/files/public/library/publications/Brochure_RoHSService_EN.pdf[2] Sound on Sound.
Has the EU Directive on Hazardous Substances (RoHS) Impacted Equipment Sales?https://www.soundonsound.com/sound-advice/q-has-eu-directive-hazardous-substances-rohs-impacted-equipment-sales[3] Digi-Key Electronics.
Lead Spacing/Bending.https://forum.digikey.com/t/lead-spacing-bending/435[4] Nichicon.
Aluminum Electrolytic Capacitors.https://www.nichicon.co.jp/english/products/pdfs/e-al_guide.pdf[5] National Aeronautics and Space Administration.
NASA Workmanship Standards.[6] National Aeronautics and Space Administration.
NASA Training Program: Student Workbook for Hand Soldering.[7] IPC.
Requirements for Soldered Electrical and Electronic Assemblies. IPC J-STD-001D.[8] Smith, Jim.
How to Achieve Perfect PCB Soldering. Sierra Circuits.
https://www.protoexpress.com/blog/how-to-achieve-perfect-pcb-soldering/[9] Roy, Akber. Is It Necessary to Clean No-Clean Flux?
Electronic Design.https://www.electronicdesign.com/industrial-automation/article/21147793/rush-pcb-is-it-necessary-to-clean-noclean-flux[10] Kester.
Green Corrosion with Rosin Flux?https://www.kester.com/Portals/0/Documents/FAQs/GreenCorrosion_Global.pdf[11] Cornell Dubilier.
Aluminum Electrolytic Capacitor Application Guide.https://www.cde.com/resources/technical-papers/AEappGuide.pdf[12] Nippon Chemi-Con.
Precautions and Guidelines (Aluminum Electrolytic Capacitors).https://chemi-con.com/wp-content/uploads/2021/04/Precautions-and-Guidelines-for-Aluminum-Electrolytic-Capacitors.pdf