Recovered components from PCBs must have quality comparable with the new ones (without damages in packages and leads, and also in working conditions) to be re-assembled again and to operate successfully during the second life. Therefore, a desoldering procedure must guarantee quality in recovered components in terms of electrical functionality and reliability in connections and package (i.e. co-planarity, lead position, no popcorn effect).
In order to identify physical damages in recovered components using the de-soldering technologies studied in task 4T2 has been used a laboratory artificial vision system (Figure 21). This system allows to obtain enlarged images of connections pins in order to assess their state (co-planarity, deformations, solder residue). On the other hand, some de-soldered components by the technologies (Hot air, IR, reflow on vapour phase) studied in the preliminary tests have been sent to Philips (partner 2) for validation. These components have been assessed in some specifications following the criteria of a new component: (1) lead coplanarity, (2) lead position, (3) popcorn effect and (4) solder residues on leads.
According to the Philips assessment carried out the conclusions are as follows:
Figure 21. Laboratory artificial vision system
De-soldered components from lead free and lead containing PCBs have been analysed with this artificial visual system. Different examples of de-soldered components with different procedures are shown below in Figures 22, 23 and 24.
Figure 22. Reflow in vapour phase de-soldering. SMD component. Board A. 10 x 10 mm, 4 x 16 pins.
Figure 23. Components de-soldered by infrared procedure.
Figure 24. Components de-soldered by hot air procedure
Later, every LQFP128 component de-soldered with the new nozzle and the hot air technology has been checked with the artificial vision system in order to examine the solder residues and the coplanarity and lead position. Examples of the pictures taken are shown below in Figures 25, 26, 27 and 28.
Figure 25. Four sides of Phlips LQFP128 component nr.10. No coplanarity damages detected.
Figure 26. Detailed image of solder residues on the pins.
Coplanarity damages are not observed in many components, but solder residues remains in leads.
Figure 27. Four sides of Thomson LQFP128 component nr.10. coplanarity damage detected.
Figure 28. Detailed image of solder residues on the pins.
Coplanarity problems have been detected in a few components as shown above.
In the most of the de-soldered components solder residues in leads have been observed. In order to remove this residue some trials have been done with components from lead-containing and lead-free solders PCBs. A combination of hot air jet and pressured air jet has been explored. The leads are heated using the hot air jet and when the solder residue is melted, and while it remains in this state, the pressured air jet removes the solder residue from the leads. This is a promising procedure but some risks has been identified:
Figure 29. Package damage (popcorn effect)
After all LQFP128 components have been checked and taken detailed photographs in the artificial vision system, the following conclusions have been obtained:
In the most of recovered components is not possible to check their specifications as it was done after the manufacturing process. Test sockets and test programs belong to components manufacturers and are usually under intellectual property. Recovered components from postconsume PCBs on a large scale for reuse purpose in new equipment could be possible but it is difficult to be accepted by manufacturers for quality reasons. An alternative would be that component manufacturers recover their own valuable electronic components from end-of-life PCBs, check them and solder again in a new PCBs.
Within this task, to estimate if the studied de-soldering systems could “kill” the components, the performance of some simple through whole components (74LS family) has been checked using a universal trainer before and after being subjected to the experimental de-soldering conditions. The results have shown all tested components worked properly (“alive”).
Focussing on hot air de-soldering procedure, different TH components have been subjected during several cycles to high temperatures simulating the de-soldering conditions for, both, lead-containing and lead-free solders. The objective was to determinate if the components stayed “alive” or not after being at this hard conditions (high temperatures) several times. The performance of these components was validated after every cycle using the universal trainer mentioned above. The result was that all components checked worked properly after being subjected to the de-soldering conditions three times.
At present, quality control of new electronic components has an estimated cost about 25-50% of their value. But this cost could be higher for recovered components from PCBs due to this process could be more complicate in this case.
Consequences of removing Pb from the composition of PCBs [next chapter]
Detection of physical damages
In order to identify physical damages in recovered components using the de-soldering technologies studied in task 4T2 has been used a laboratory artificial vision system (Figure 21). This system allows to obtain enlarged images of connections pins in order to assess their state (co-planarity, deformations, solder residue). On the other hand, some de-soldered components by the technologies (Hot air, IR, reflow on vapour phase) studied in the preliminary tests have been sent to Philips (partner 2) for validation. These components have been assessed in some specifications following the criteria of a new component: (1) lead coplanarity, (2) lead position, (3) popcorn effect and (4) solder residues on leads.
According to the Philips assessment carried out the conclusions are as follows:
- No overheating and mechanical damage of the components has been observed (no popcorn effect).
- The main problems are the lost of coplanarity in some components and solder residues on leads, this fact makes more difficult reutilization of recovered components in a mass production factory (to solve those problems de-soldering parameters must be optimised). However, these components could be used in repair shops after removing solders residues, applying a new tin finish, repositioning leads looking to X-Y position and coplanarity and electrical testing. The best results have been obtained in components de-soldered by hot air.
Figure 21. Laboratory artificial vision system
De-soldered components from lead free and lead containing PCBs have been analysed with this artificial visual system. Different examples of de-soldered components with different procedures are shown below in Figures 22, 23 and 24.
Figure 22. Reflow in vapour phase de-soldering. SMD component. Board A. 10 x 10 mm, 4 x 16 pins.
Figure 23. Components de-soldered by infrared procedure.
Figure 24. Components de-soldered by hot air procedure
Later, every LQFP128 component de-soldered with the new nozzle and the hot air technology has been checked with the artificial vision system in order to examine the solder residues and the coplanarity and lead position. Examples of the pictures taken are shown below in Figures 25, 26, 27 and 28.
Figure 25. Four sides of Phlips LQFP128 component nr.10. No coplanarity damages detected.
Figure 26. Detailed image of solder residues on the pins.
Coplanarity damages are not observed in many components, but solder residues remains in leads.
Figure 27. Four sides of Thomson LQFP128 component nr.10. coplanarity damage detected.
Figure 28. Detailed image of solder residues on the pins.
Coplanarity problems have been detected in a few components as shown above.
In the most of the de-soldered components solder residues in leads have been observed. In order to remove this residue some trials have been done with components from lead-containing and lead-free solders PCBs. A combination of hot air jet and pressured air jet has been explored. The leads are heated using the hot air jet and when the solder residue is melted, and while it remains in this state, the pressured air jet removes the solder residue from the leads. This is a promising procedure but some risks has been identified:
- The component is subjected an extra overheating and thus, the package could be damaged (popcorn effect). In Figure 29 this situation is shown, and the image corresponds to a LQFP128 component from a lead-free Test Board. In this case very high temperatures have been needed to re-melt solder residue and the package has been overheating. For lead-containing solders this risk is less important.
- The pressure of the air jet must be controlled and adapted to the features of the component in order to preserve the alignment and coplanarity of leads.
Figure 29. Package damage (popcorn effect)
After all LQFP128 components have been checked and taken detailed photographs in the artificial vision system, the following conclusions have been obtained:
- Solder residues remain on all de-soldered components.
- 76% of components are free of alignment problems in leads. It is important to indicate that the system used in this task is not so accurate as the ones used in electronics industry, and therefore, more damages may be detected.
- 17% of the components have coplanarity and alignment defects.
- 7% of the components have solder bridges between leads.
Performance damage analysis
In the most of recovered components is not possible to check their specifications as it was done after the manufacturing process. Test sockets and test programs belong to components manufacturers and are usually under intellectual property. Recovered components from postconsume PCBs on a large scale for reuse purpose in new equipment could be possible but it is difficult to be accepted by manufacturers for quality reasons. An alternative would be that component manufacturers recover their own valuable electronic components from end-of-life PCBs, check them and solder again in a new PCBs.
Within this task, to estimate if the studied de-soldering systems could “kill” the components, the performance of some simple through whole components (74LS family) has been checked using a universal trainer before and after being subjected to the experimental de-soldering conditions. The results have shown all tested components worked properly (“alive”).
Focussing on hot air de-soldering procedure, different TH components have been subjected during several cycles to high temperatures simulating the de-soldering conditions for, both, lead-containing and lead-free solders. The objective was to determinate if the components stayed “alive” or not after being at this hard conditions (high temperatures) several times. The performance of these components was validated after every cycle using the universal trainer mentioned above. The result was that all components checked worked properly after being subjected to the de-soldering conditions three times.
At present, quality control of new electronic components has an estimated cost about 25-50% of their value. But this cost could be higher for recovered components from PCBs due to this process could be more complicate in this case.
Consequences of removing Pb from the composition of PCBs [next chapter]
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