pinchemotherloaf
Well-known member
I have first hand experience with wave soldering, hand soldering and smt soldering. I made mil spec Intel mainframes in 1980-1983. I have soldered 1000s of pcb and related components.
Here are my thoughts on the matter:
Wave soldering for TH is perfectly fine and yields excellent results, if done properly. This includes using contaminant free pcbs and component leads, flux and solder types, temperature, handling freshly soldered pcbs, time from soldering to neutralization (using acid flux).
Contamination of pcb pads, barrels and component leads will cause poor results, including little explosions at the joint during soldering. The joint will be compromised and must be touched up (if possible.) The purpose of flux is to burn off contamination but even flux and heat are not always enough. Contamination , when it occured, was common to the entire pcb in my time, not just a pad or two. Component leads were an issue as well, even if the pcb was clean.
Leaded solder is the only acceptable solder, lead free solder will always be problematic over time. I understand that lead is on the no-no list, however 60/40 leaded solder is the only formula I used and still do. Unleaded solder does not produce a 'shiny' joint. It produces a joint that appears cold, no matter how it's applied.
Regardless of other opinions, Acid Flux is perfectly acceptable. We used a foaming acid flux made of orange peel. It must be neutralized with baking soda and water fairly quickly after being used, BUT not too quickly as to fracture the solder. Rosin flux, of course, is acceptable but more difficult to clean off than orange peel residue. We did not use rosin for wave soldering (or even touch up.) It would produce way too much smoke and need lots of Freon to clean up.
Soldering temperature is critical. The melting point is somewhere around 400 deg F. To have good flow, to all pads, barrels and leads need high temperature must be kept on a long as needed, Without damaging the components. We would pre-heat the pcb (with a type of stove in the wave machine) after fluxing and before waving. There is an optimum amount of time involved. This is accomplished by adjusting the chain speed. The wave pumps must be optimized to allow leads into the wave and not drown the pcb accidentally. We would hold the front of the pcb with an orange stick to prevent drowning, right as the pcb entered the wave.
Solder curing is rapid but solder must not be disturbed at all during cure time, about 2-3 minutes. If using acid flux neutralizing must be done quickly, as as not to tarnish the solder, but not too soon as to fracture solder by cooling to fast. We would have a bath of warm water and baking soda with scrub brushes to quickly clean the pcb. Any components that could not be submersed would be hand soldered later.
Of course, hand soldering will always be the best practice if producing really good quality soldering. Wave soldering is for making many, many pcbs at the lowest cost. Most wave soldered pcbs have been touched up, if done properly. You can see on some pcbs, that are usually missing solder on top, that have not been touched up. Some might say that touch up is not needed as, sometimes, the pad is not connected to a trace. That is incorrect. All pads should be soldered regardless of trace present or not. Very rarely, does a wave soldered pcb not need any touch up. Maybe only 1 in 500.
Joints should be about 2/3 the amount of solder needed to make joint a perfect 45 deg., but not too little. They should look exponential rising from the edge of the pad up the lead. just a few mm depending on pad and lead size. Clipping should be just above the joint, maybe 1 mm, but not into the joint at all.
Regarding soldering in high impedance circuits (like adding a 10g smt resistor to your bias, the amount of solder, if excessive, might produce unwanted noise. This is from a respected source on the subject I learned from 20 years ago while professionally building microphones.
Here are my thoughts on the matter:
Wave soldering for TH is perfectly fine and yields excellent results, if done properly. This includes using contaminant free pcbs and component leads, flux and solder types, temperature, handling freshly soldered pcbs, time from soldering to neutralization (using acid flux).
Contamination of pcb pads, barrels and component leads will cause poor results, including little explosions at the joint during soldering. The joint will be compromised and must be touched up (if possible.) The purpose of flux is to burn off contamination but even flux and heat are not always enough. Contamination , when it occured, was common to the entire pcb in my time, not just a pad or two. Component leads were an issue as well, even if the pcb was clean.
Leaded solder is the only acceptable solder, lead free solder will always be problematic over time. I understand that lead is on the no-no list, however 60/40 leaded solder is the only formula I used and still do. Unleaded solder does not produce a 'shiny' joint. It produces a joint that appears cold, no matter how it's applied.
Regardless of other opinions, Acid Flux is perfectly acceptable. We used a foaming acid flux made of orange peel. It must be neutralized with baking soda and water fairly quickly after being used, BUT not too quickly as to fracture the solder. Rosin flux, of course, is acceptable but more difficult to clean off than orange peel residue. We did not use rosin for wave soldering (or even touch up.) It would produce way too much smoke and need lots of Freon to clean up.
Soldering temperature is critical. The melting point is somewhere around 400 deg F. To have good flow, to all pads, barrels and leads need high temperature must be kept on a long as needed, Without damaging the components. We would pre-heat the pcb (with a type of stove in the wave machine) after fluxing and before waving. There is an optimum amount of time involved. This is accomplished by adjusting the chain speed. The wave pumps must be optimized to allow leads into the wave and not drown the pcb accidentally. We would hold the front of the pcb with an orange stick to prevent drowning, right as the pcb entered the wave.
Solder curing is rapid but solder must not be disturbed at all during cure time, about 2-3 minutes. If using acid flux neutralizing must be done quickly, as as not to tarnish the solder, but not too soon as to fracture solder by cooling to fast. We would have a bath of warm water and baking soda with scrub brushes to quickly clean the pcb. Any components that could not be submersed would be hand soldered later.
Of course, hand soldering will always be the best practice if producing really good quality soldering. Wave soldering is for making many, many pcbs at the lowest cost. Most wave soldered pcbs have been touched up, if done properly. You can see on some pcbs, that are usually missing solder on top, that have not been touched up. Some might say that touch up is not needed as, sometimes, the pad is not connected to a trace. That is incorrect. All pads should be soldered regardless of trace present or not. Very rarely, does a wave soldered pcb not need any touch up. Maybe only 1 in 500.
Joints should be about 2/3 the amount of solder needed to make joint a perfect 45 deg., but not too little. They should look exponential rising from the edge of the pad up the lead. just a few mm depending on pad and lead size. Clipping should be just above the joint, maybe 1 mm, but not into the joint at all.
Regarding soldering in high impedance circuits (like adding a 10g smt resistor to your bias, the amount of solder, if excessive, might produce unwanted noise. This is from a respected source on the subject I learned from 20 years ago while professionally building microphones.
Last edited:
