potcore
Electrical
- Feb 26, 2007
- 28
Dear Engineers
Sorry that this is about soldering, it's just that i'm an electronic engineer inbetween jobs....today a recruitment agency kindly sent me for a soldering test at a local electronics company so that i could hopefully do some soldering work till the next electronics job comes up...I failed the soldering test -but believe that my poor solder joints were due to the company's poor equipment rather than my technique. I am worried that the agency will now not refer me for other soldering jobs....I would be very grateful if you could analyse my (following) letter to the agency and provide any thoughts on whether you believe i am correct to criticise the company's soldering set-up. The company was a high-tech comms company and there were no other solderers working there -just electronic engineers. The soldering test involved surface mount 0402 resistors and capacitors.......(ive subbed in the name "electro-save" for the comapny's actual name)....
Hi,
Thankyou for arranging todays soldering test at Electro-save. I fully respect their decision not to employ me and have no complaint whatsoever, -whatever their reasons for deciding against employing myself. I am extremely grateful for their time and consideration.
With reference to this Electro-save soldering contract where I was not selected for employment, I am hoping that I can provide some kind of assurance that my soldering skills are not as bad as my performance at Electro-save may suggest. I am hoping that your office may not be deterred from putting me forward for such soldering contracts at other companies.
During the soldering test, I noticed that the solder was not “wetting” or “running” as it should. “Wetting” is where the heated solder momentarily becomes “water-ish” and flows over the work, -intimately clinging itself to the shapes of the work. When “wetting” occurs, one sees the solder flow over the work, and there is sometimes a momentary glint of light as the solder “envelope” changes shape and momentarily reflects light toward the eye. –This did not occur at Electro-save, -the solder merely “sludged” without flowing. –I feel that this is in some way due to the set-up of the soldering system at Electro-save. It is indeed possible to learn to “sludge-solder” with reasonable results, though it is not recommended and is bad practice.
I have previously soldered such things as 0.5mm pitch ICs with excellent results. –Indeed, when soldering these components, I noticed the solder actually starting to flow up the pins of the IC’s , as it should. –At Electro-save, such flowing of the solder did not occur.
-At Electro-save, even when I simultaneously touched the solder onto the solder_iron_tip and the pad as an experiment, the solder did not flow over the pad as it should –instead the solder just “sludged-up”. –This suggests a problem with their soldering set-up.
Firstly, the “sludging” seen at Electro-save was partly due to the fact that the PCB pads on which I had to solder were slightly “yellowed” with oxide. Usually, flux-cored solder would act so as to remove this oxide coating, allowing the solder to “run” and flow over the work. It was evident that the solder with which I was provided did not contain much flux, -since there was an absence of flux residue on the work after it had been soldered (flux residue can easily be cleaned off with a suitable cleaning agent) –This lack of flux was one reason why the solder would not flow properly for me.
Solder that has a sufficient helping of flux in its core produces fumes with a distinctive smell. I did not notice this smell with the solder that I was provided with at Electro-save. –Flux was always going to be necessary with the slightly “yellowed” 0402 pads that I experienced at Electro-save. I feel that this may have been why the solder would not flow properly for me.
Electro-save staff did however provide me with a flux pen, -though this was dry of flux. –This is a problem with flux pens, and is the reason why flux-syringes provide for better application of flux. (I was not provided with a flux syringe at Electro-save). Alternatively, a pot of flux and a fine point to allow application of flux to the pad is OK.
Another reason that may have prevented the solder from flowing adequately at Electro-save, was the fact that the solder was slightly too thick in diameter and the solder_iron_tip was slightly too thick.
Also, for soldering 0402 components, one really needs a soldering iron with a settable temperature so that the tip temperature can be optimised for the work. Also, the tip temperature should preferrably be maintained constant by a temperature feedback system. (This prevents the solder tip from cooling when applied to the work) The irons at Electro-save had no settable temperature. I am unsure as to whether or not the irons at Electro-save had temperature feedback control.
PCB’s with pads meant for hand soldering sometimes have “necked” pads to facilitate hand soldering. (A “necked” pad is a pad for which the adjoining PCB track becomes narrower just prior to meeting with the pad) –The “neck” is good as it prevents heat from the iron “running away” along the adjoining track. –If an iron has no temperature feedback control, then there is no correction for the cooling of the tip that occurs when the tip is applied to the non-necked pad. –Under this circumstance, the solder may not be heated enough to allow it to flow properly –and insufficient solder flow was what I actually experienced at Electro-save.
Most PCB’s are populated using flow solder machines (as opposed to hand soldering), and “necked” pads are not necessary, as the work is sufficiently heated by the solder flow machine. I suspect the PCB’s with which I was provided at Electro-save had non-necked pads –as a consequence, I suspect that the work may not have been sufficiently heated by the iron that I was using –thus causing a deficiency in the flow of the solder which was heated with what may have been a non-temperature_regulated iron.
Another thing that worked to my disadvantage was that the solder braid with which I was provided was much too wide. Solder braid should be no wider than the widest dimension of the pad being cleaned of solder. –However, the braid with which I was provided was over 4 times wider than the widest dimension of the 0402 pads.
-Solder braid that is too wide can damage the pad that it is being used to clean, since it conducts more heat away and may cool and stick to the pad, resulting in damage to or removal of the pad.
The soldering iron with which I was provided also had a deliberately bent tip. These bent tips can sometimes be useful, though if the iron is not at the right temperature, these bent tips are less than useful. –This is because solder tends to “clag” up in the bend of the tip, -this “clag” of solder then acts to consume heat from the solder tip, meaning that the work is not heated to the temperature that it should be. Also, the lump or “clag” of solder tends to make the tip less fine –and the tip needs to be finely pointed for soldering 0402 capacitors and resistors.
Also, since the “clagged” solder becomes trapped within the bend of the tip, it is rather difficult to remove with the solder sponge.
At other electronics companies where I have selected soldering irons, tips, solder and flux myself, I have had no trouble soldering 0402 resistors and capacitors. –For some reason, the solder just would not flow for me at Electro-save. I did my best to try and keep the tip clean (even though the solder sponge was dirty) and applied a light tin to the solder_tip prior to appying the tip to the work.
Another problem was that the tweezers with which I was provided were magnetised –this made it awkward to grasp the 0402 capacitors without the capacitor swinging up to the tweezers and sticking to them in the wrong position. One then had to handle the 0402 capacitor to try and get it off the tweezers…-thus putting sweat onto the capacitor contacts, which does not assist in its subsequent soldering.
Soldering systems for hand soldering 0402 surface-mount capacitors and resistors should be srupulously specified. At Electro-save it was not possible to set the solder tip temperature –also there was no indication as to what the solder tip temperature actually was.
At times I actually noticed that the solder was “spiking” up from the work –this actually suggests that the iron was too hot. (I did not apply the tip to the work for too long a time) -However, there was no means by which I could adjust the temperature of the soldering iron. I also sometimes noticed that when the solder was simultaneously touched to the pad and the component and the solder_tip, -the solder actually just streamed up the solder_tip itself rather than going over the work –This again suggests that the solder_tip was too hot for soldering to that particular pad.
Please don’t let this seem like sour-grapes, -it’s just that I have not experienced such problems with soldering in other companies, and would hope that your office may not be deterred from seeking soldering contracts for myself at other places.
Regards,
Sorry that this is about soldering, it's just that i'm an electronic engineer inbetween jobs....today a recruitment agency kindly sent me for a soldering test at a local electronics company so that i could hopefully do some soldering work till the next electronics job comes up...I failed the soldering test -but believe that my poor solder joints were due to the company's poor equipment rather than my technique. I am worried that the agency will now not refer me for other soldering jobs....I would be very grateful if you could analyse my (following) letter to the agency and provide any thoughts on whether you believe i am correct to criticise the company's soldering set-up. The company was a high-tech comms company and there were no other solderers working there -just electronic engineers. The soldering test involved surface mount 0402 resistors and capacitors.......(ive subbed in the name "electro-save" for the comapny's actual name)....
Hi,
Thankyou for arranging todays soldering test at Electro-save. I fully respect their decision not to employ me and have no complaint whatsoever, -whatever their reasons for deciding against employing myself. I am extremely grateful for their time and consideration.
With reference to this Electro-save soldering contract where I was not selected for employment, I am hoping that I can provide some kind of assurance that my soldering skills are not as bad as my performance at Electro-save may suggest. I am hoping that your office may not be deterred from putting me forward for such soldering contracts at other companies.
During the soldering test, I noticed that the solder was not “wetting” or “running” as it should. “Wetting” is where the heated solder momentarily becomes “water-ish” and flows over the work, -intimately clinging itself to the shapes of the work. When “wetting” occurs, one sees the solder flow over the work, and there is sometimes a momentary glint of light as the solder “envelope” changes shape and momentarily reflects light toward the eye. –This did not occur at Electro-save, -the solder merely “sludged” without flowing. –I feel that this is in some way due to the set-up of the soldering system at Electro-save. It is indeed possible to learn to “sludge-solder” with reasonable results, though it is not recommended and is bad practice.
I have previously soldered such things as 0.5mm pitch ICs with excellent results. –Indeed, when soldering these components, I noticed the solder actually starting to flow up the pins of the IC’s , as it should. –At Electro-save, such flowing of the solder did not occur.
-At Electro-save, even when I simultaneously touched the solder onto the solder_iron_tip and the pad as an experiment, the solder did not flow over the pad as it should –instead the solder just “sludged-up”. –This suggests a problem with their soldering set-up.
Firstly, the “sludging” seen at Electro-save was partly due to the fact that the PCB pads on which I had to solder were slightly “yellowed” with oxide. Usually, flux-cored solder would act so as to remove this oxide coating, allowing the solder to “run” and flow over the work. It was evident that the solder with which I was provided did not contain much flux, -since there was an absence of flux residue on the work after it had been soldered (flux residue can easily be cleaned off with a suitable cleaning agent) –This lack of flux was one reason why the solder would not flow properly for me.
Solder that has a sufficient helping of flux in its core produces fumes with a distinctive smell. I did not notice this smell with the solder that I was provided with at Electro-save. –Flux was always going to be necessary with the slightly “yellowed” 0402 pads that I experienced at Electro-save. I feel that this may have been why the solder would not flow properly for me.
Electro-save staff did however provide me with a flux pen, -though this was dry of flux. –This is a problem with flux pens, and is the reason why flux-syringes provide for better application of flux. (I was not provided with a flux syringe at Electro-save). Alternatively, a pot of flux and a fine point to allow application of flux to the pad is OK.
Another reason that may have prevented the solder from flowing adequately at Electro-save, was the fact that the solder was slightly too thick in diameter and the solder_iron_tip was slightly too thick.
Also, for soldering 0402 components, one really needs a soldering iron with a settable temperature so that the tip temperature can be optimised for the work. Also, the tip temperature should preferrably be maintained constant by a temperature feedback system. (This prevents the solder tip from cooling when applied to the work) The irons at Electro-save had no settable temperature. I am unsure as to whether or not the irons at Electro-save had temperature feedback control.
PCB’s with pads meant for hand soldering sometimes have “necked” pads to facilitate hand soldering. (A “necked” pad is a pad for which the adjoining PCB track becomes narrower just prior to meeting with the pad) –The “neck” is good as it prevents heat from the iron “running away” along the adjoining track. –If an iron has no temperature feedback control, then there is no correction for the cooling of the tip that occurs when the tip is applied to the non-necked pad. –Under this circumstance, the solder may not be heated enough to allow it to flow properly –and insufficient solder flow was what I actually experienced at Electro-save.
Most PCB’s are populated using flow solder machines (as opposed to hand soldering), and “necked” pads are not necessary, as the work is sufficiently heated by the solder flow machine. I suspect the PCB’s with which I was provided at Electro-save had non-necked pads –as a consequence, I suspect that the work may not have been sufficiently heated by the iron that I was using –thus causing a deficiency in the flow of the solder which was heated with what may have been a non-temperature_regulated iron.
Another thing that worked to my disadvantage was that the solder braid with which I was provided was much too wide. Solder braid should be no wider than the widest dimension of the pad being cleaned of solder. –However, the braid with which I was provided was over 4 times wider than the widest dimension of the 0402 pads.
-Solder braid that is too wide can damage the pad that it is being used to clean, since it conducts more heat away and may cool and stick to the pad, resulting in damage to or removal of the pad.
The soldering iron with which I was provided also had a deliberately bent tip. These bent tips can sometimes be useful, though if the iron is not at the right temperature, these bent tips are less than useful. –This is because solder tends to “clag” up in the bend of the tip, -this “clag” of solder then acts to consume heat from the solder tip, meaning that the work is not heated to the temperature that it should be. Also, the lump or “clag” of solder tends to make the tip less fine –and the tip needs to be finely pointed for soldering 0402 capacitors and resistors.
Also, since the “clagged” solder becomes trapped within the bend of the tip, it is rather difficult to remove with the solder sponge.
At other electronics companies where I have selected soldering irons, tips, solder and flux myself, I have had no trouble soldering 0402 resistors and capacitors. –For some reason, the solder just would not flow for me at Electro-save. I did my best to try and keep the tip clean (even though the solder sponge was dirty) and applied a light tin to the solder_tip prior to appying the tip to the work.
Another problem was that the tweezers with which I was provided were magnetised –this made it awkward to grasp the 0402 capacitors without the capacitor swinging up to the tweezers and sticking to them in the wrong position. One then had to handle the 0402 capacitor to try and get it off the tweezers…-thus putting sweat onto the capacitor contacts, which does not assist in its subsequent soldering.
Soldering systems for hand soldering 0402 surface-mount capacitors and resistors should be srupulously specified. At Electro-save it was not possible to set the solder tip temperature –also there was no indication as to what the solder tip temperature actually was.
At times I actually noticed that the solder was “spiking” up from the work –this actually suggests that the iron was too hot. (I did not apply the tip to the work for too long a time) -However, there was no means by which I could adjust the temperature of the soldering iron. I also sometimes noticed that when the solder was simultaneously touched to the pad and the component and the solder_tip, -the solder actually just streamed up the solder_tip itself rather than going over the work –This again suggests that the solder_tip was too hot for soldering to that particular pad.
Please don’t let this seem like sour-grapes, -it’s just that I have not experienced such problems with soldering in other companies, and would hope that your office may not be deterred from seeking soldering contracts for myself at other places.
Regards,
