To PCB or not to PCB?

[nigelwright7557]

Originally Posted by jean-paul

Often people solder and then cut the wire which gives mechanical stress on the joint which will shorten its lifespan/reliability.

Thi is only a problem ifyou cut through the solder as well as the wire.
I always cut just above the soldered joint.

[jean-paul]

NO ! I heard this so many times. When you use standard pliers you will always put some force on the joint while cutting it. This is a fact not some story. That is why special pliers are made for electronics by Knipex etc. Standard pliers have an angle in which they cut and while cutting they will pull the wire up which is force in my book. I use special Knipex cutters and the angle they cut has been optimized for putting the least stress on the joint as possible but still...

If it is not the pliers it will be your hands putting some force on the wire/joint when cutting. This can easily be avoided by doing it the other way around which costs nothing in terms of money or time. Just think different and try it out. Joints also look better when they're cut first and the surface that was cut will be tinned too which leaves not a chance for corrosion of the otherwise bare copper. Only this should be reason enough for "cutting first".

In military stuff the rule is : "first cut then solder"....

[nigelwright7557]

Originally Posted by jean-paul

NO ! I heard this so many times. When you use standard pliers you will always put some force on the joint while cutting it.
In military stuff the rule is : "first cut then solder"....

I always use light side cutters, pliers are a bit heavy and liable to put a lot of stress on the joint. Cant say I have had any problems in 30 years of soldering with broken joints.

[jean-paul]

Category "I drink and drive for 30 years and never had an accident" I can tell joints will break down earlier on power electronics etc. where hefty currents flow through solder joints but don't take my word for it and simply try it out once. I realize myself that longevity is a rare item in modern society so maybe debating the subject is pointless. The device will end up in the bin before the joints will break. Still I hope airplanes are built according these old fashioned standards.

It is quite possible I used the wrong words in english to name a tool as english is not the language I use everyday. I meant these of course:

[counter culture]

Originally Posted by jean-paul

That is why special pliers are made for electronics by Knipex etc.

In military stuff the rule is : "first cut then solder"....

I think this is advertising propaganda originated by Knipex or some other tool manufacturer, or more likely an old wives tale (not uncommon in the military).

Think about the difficulty of developing data on the subject. You'd have to have failure mode analysis data developed from identical products, some cut before and some cut after soldering, all identified as to which was which.

I worked in a Racal (now Vodafone) factory producing military radios. We produced many thru-hole PCBs hand-stuffed on manual pick-and-place machines. The leads were all automatically trimmed on a machine after soldering.

As far as PCBs are concerned, the big advantage of a computer-produced PCB is the low likelihood of connectivity issues if the schematic is correctly drawn and the repeatability. The more complex the design, the greater the probability of error in point-to-point wiring and on perfboard.

[nigelwright7557]

Originally Posted by counter culture

I think this is advertising propaganda originated by Knipex or some other tool manufacturer, or more likely an old wives tale (not uncommon in the military).
ard.

I was trained to the DEF2000 standard and we were never told to cut first.

[jean-paul]

Originally Posted by counter culture

I think this is advertising propaganda originated by Knipex or some other tool manufacturer, or more likely an old wives tale (not uncommon in the military).

Think about the difficulty of developing data on the subject. You'd have to have failure mode analysis data developed from identical products, some cut before and some cut after soldering, all identified as to which was which.

It is sometimes difficult to accept a different truth. It is simple: when you don't apply mechanical force at all chances are likely that the joint will live longer. Same kind of truth like: you don't need to clean stuff if you don't make it dirty etc.

Originally Posted by counter culture

I worked in a Racal (now Vodafone) factory producing military radios. We produced many thru-hole PCBs hand-stuffed on manual pick-and-place machines. The leads were all automatically trimmed on a machine after soldering.

They were trimmed and not cut I guess ? AFAIK this is done with high speed rotary cutters (for a reason).