Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Christoph Prem

#13972

DPM-Rate for SMT pprocess | 5 October, 1998

Does sombbody know what DPM rate a good and reliable SMT assembly line (incl. solder paste print, assembly and feflow soldering) has?

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Tony B

#13973

Re: DPM-Rate for SMT pprocess | 6 October, 1998

| Does sombbody know what DPM rate a good and reliable SMT assembly line (incl. solder paste print, assembly and feflow soldering) has? | Chris, It may be helpful if you could translate DPM into a meaningful phrase as many people (myself included) may not understand the abbreviation. Look forward to its expansion.

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Charles Stringer

#13974

Re: DPM-Rate for SMT pprocess | 6 October, 1998

| Does sombbody know what DPM rate a good and reliable SMT assembly line (incl. solder paste print, assembly and feflow soldering) has? | DPM is Defects per million, usually measured on components. We run a process consisting of small to medium batch manufacture typically 250,000 components placed per week up to 10 different circuit board types each day. We use DEK 265 screen printer 2 Siemens Siplace placement machines and a surf systems reflow oven. Our DPM rate (as measured at in circuit test) is typically 40dpm. If you would like to know more, email me directly.

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Mike C

#13975

Re: DPM-Rate for SMT pprocess | 6 October, 1998

| | Does sombbody know what DPM rate a good and reliable SMT assembly line (incl. solder paste print, assembly and feflow soldering) has? | | DPM is Defects per million, usually measured on components. We run a process consisting of small to medium batch manufacture typically 250,000 components placed per week up to 10 different circuit board types each day. We use DEK 265 screen printer 2 Siemens Siplace placement machines and a surf systems reflow oven. Our DPM rate (as measured at in circuit test) is typically 40dpm. If you would like to know more, email me directly. | Using DPM (Defects Per Million) as a process indicator at test may not be indicative of how well your processes are running. 40 DPM at test may sound good but if you have an army of inspectors and rework people working on the boards your yields may be ok but all of your profits have been spent. You should consider you�re in process DPM or a cumulation of defects found throughout your process(before rework). As an example if a given number of boards were found to have 100 defects at SMT and another 200 at Wave Solder, then the in process DPM would be calculated with the 300 defects.

Something else to consider... (And this is just my opinion) 1) How a defect is calculated. At the SMT process if you have one 144 pin QFP that is placed off pad then that would be considered one defect (placement). On the other hand if that part has 30 pins with insufficient solder then that would be 30 defects and so on.

2) How to Calculate DPMO (Defects per Million of Opportunity). I use the number of solder joints + The number of components = DPMO Now some people will argue that the component should be counted as several possible defects Placed off pad, Wrong polarity, coplanarity, wrong part and so on. I still consider 1 component as 1 DPMO, but I track what caused the defect for my process improvement.

In Answer to the original question we use under 100 DPM for SMT (for most assemblies). In some cases the DPM will Fluctuate from Assembly to assembly due to poor layout, design, inferior components (I'm finger pointing here, there's no way it could be engineering) and so on.

Well that�s my 2 cents

Mike

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Christoph Prem

#13976

Re: DPM-Rate for SMT pprocess | 7 October, 1998

| | Does sombbody know what DPM rate a good and reliable SMT assembly line (incl. solder paste print, assembly and feflow soldering) has? | | | Chris, | It may be helpful if you could translate DPM into a meaningful phrase as many people (myself included) may not understand the abbreviation. | Look forward to its expansion.

| DPM: Defaults Per Million That means when you have 1.000.000 solder joints, how many of them are bad ones

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Charles Stringer

#13977

Re: DPM-Rate for SMT pprocess | 7 October, 1998

| | | Does sombbody know what DPM rate a good and reliable SMT assembly line (incl. solder paste print, assembly and feflow soldering) has? | | | DPM is Defects per million, usually measured on components. We run a process consisting of small to medium batch manufacture typically 250,000 components placed per week up to 10 different circuit board types each day. We use DEK 265 screen printer 2 Siemens Siplace placement machines and a surf systems reflow oven. Our DPM rate (as measured at in circuit test) is typically 40dpm. If you would like to know more, email me directly. | | | Using DPM (Defects Per Million) as a process indicator at test may not be indicative of how well your processes are running. 40 DPM at test may sound good but if you have an army of inspectors and rework people working on the boards your yields may be ok but all of your profits have been spent. You should consider you�re in process DPM or a cumulation of defects found throughout your process(before rework). As an example if a given number of boards were found to have 100 defects at SMT and another 200 at Wave Solder, then the in process DPM would be calculated with the 300 defects. | | Something else to consider... | (And this is just my opinion) | 1) How a defect is calculated. At the SMT process if you have one 144 pin QFP that is placed off pad then that would be considered one defect (placement). On the other hand if that part has 30 pins with insufficient solder then that would be 30 defects and so on. | | 2) How to Calculate DPMO (Defects per Million of Opportunity). I use the number of solder joints + The number of components = DPMO | Now some people will argue that the component should be counted as several possible defects | Placed off pad, Wrong polarity, coplanarity, wrong part and so on. I still consider 1 component as 1 DPMO, but I track what caused the defect for my process improvement. | | In Answer to the original question | we use under 100 DPM for SMT (for most assemblies). | In some cases the DPM will Fluctuate from Assembly to assembly due to poor layout, design, inferior components (I'm finger pointing here, there's no way it could be engineering) and so on. | | | Well that�s my 2 cents | | Mike | Mike Thanks for a more detailed breakdown of measuring defect rate. Ours is based around incircuit test. before that point we have no formal inspection process, operators are responsible for their own output quality. At ICT we record the defect against the device with the problem e.g.sm capactor etc. The defect database has a link into our manufcturing database and can identify at which workcenter the component was fitted, hence the defect is attributed to that process. If you would like more details email me direct and I can send you sample outputs

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Eric R

#13978

Re: DPM-Rate for SMT pprocess | 8 October, 1998

| | | Does sombbody know what DPM rate a good and reliable SMT assembly line (incl. solder paste print, assembly and feflow soldering) has? | | | DPM is Defects per million, usually measured on components. We run a process consisting of small to medium batch manufacture typically 250,000 components placed per week up to 10 different circuit board types each day. We use DEK 265 screen printer 2 Siemens Siplace placement machines and a surf systems reflow oven. Our DPM rate (as measured at in circuit test) is typically 40dpm. If you would like to know more, email me directly. | | | Using DPM (Defects Per Million) as a process indicator at test may not be indicative of how well your processes are running. 40 DPM at test may sound good but if you have an army of inspectors and rework people working on the boards your yields may be ok but all of your profits have been spent. You should consider you�re in process DPM or a cumulation of defects found throughout your process(before rework). As an example if a given number of boards were found to have 100 defects at SMT and another 200 at Wave Solder, then the in process DPM would be calculated with the 300 defects. | | Something else to consider... | (And this is just my opinion) | 1) How a defect is calculated. At the SMT process if you have one 144 pin QFP that is placed off pad then that would be considered one defect (placement). On the other hand if that part has 30 pins with insufficient solder then that would be 30 defects and so on. | | 2) How to Calculate DPMO (Defects per Million of Opportunity). I use the number of solder joints + The number of components = DPMO | Now some people will argue that the component should be counted as several possible defects | Placed off pad, Wrong polarity, coplanarity, wrong part and so on. I still consider 1 component as 1 DPMO, but I track what caused the defect for my process improvement. | | In Answer to the original question | we use under 100 DPM for SMT (for most assemblies). | In some cases the DPM will Fluctuate from Assembly to assembly due to poor layout, design, inferior components (I'm finger pointing here, there's no way it could be engineering) and so on. | | | Well that�s my 2 cents | | Mike |

Mike, pretty sound observations and opinions. I agree, but then again I come from the 'manufacturing' side of things with a very careful eye out for our quality and process controls. Try convincing our QA and upper management on that and, hey !!

Oh well. Again, kudos!

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Scott Lolmaugh

#13979

Re: DPM-Rate for SMT pprocess | 18 November, 1998

| | | Does sombbody know what DPM rate a good and reliable SMT assembly line (incl. solder paste print, assembly and feflow soldering) has? | | | | | Chris, | | It may be helpful if you could translate DPM into a meaningful phrase as many people (myself included) may not understand the abbreviation. | | Look forward to its expansion. | | | DPM: Defaults Per Million | That means when you have 1.000.000 solder joints, how many of them are bad ones | | | Actually, it depends on what is defined as a defect opportunity. If you define 1 opportunity per component, then it means, when you have a million parts assembled, how many of them have a defect caused by SMT processes. In other words, there are many defect types that could be present at any single part on a single board, but if there is any defect at all, you determine the "main" one and only count it as one defect. For instance, if an SOIC-8 is mis-oriented 180 degrees, and it is also more than allowed off the pads, and 4 leads have no solder, and...etc. You could tally up 1-misoriented + 8-misaligned + 4-no-solder...etc. against that one part. In order to do that level of detail, you need to calculate your DPM rate using all the possible defect opportunities for each part on the board. I think it's a lot easier to just have 1 defect/ opportunity per part.

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Scott Lolmaugh

#13980

Re: DPM-Rate for SMT pprocess | 18 November, 1998

| | | | Does sombbody know what DPM rate a good and reliable SMT assembly line (incl. solder paste print, assembly and feflow soldering) has? | | | | DPM is Defects per million, usually measured on components. We run a process consisting of small to medium batch manufacture typically 250,000 components placed per week up to 10 different circuit board types each day. We use DEK 265 screen printer 2 Siemens Siplace placement machines and a surf systems reflow oven. Our DPM rate (as measured at in circuit test) is typically 40dpm. If you would like to know more, email me directly. | | | | | Using DPM (Defects Per Million) as a process indicator at test may not be indicative of how well your processes are running. 40 DPM at test may sound good but if you have an army of inspectors and rework people working on the boards your yields may be ok but all of your profits have been spent. You should consider you�re in process DPM or a cumulation of defects found throughout your process(before rework). As an example if a given number of boards were found to have 100 defects at SMT and another 200 at Wave Solder, then the in process DPM would be calculated with the 300 defects. | | | | Something else to consider... | | (And this is just my opinion) | | 1) How a defect is calculated. At the SMT process if you have one 144 pin QFP that is placed off pad then that would be considered one defect (placement). On the other hand if that part has 30 pins with insufficient solder then that would be 30 defects and so on. | | | | 2) How to Calculate DPMO (Defects per Million of Opportunity). I use the number of solder joints + The number of components = DPMO | | Now some people will argue that the component should be counted as several possible defects | | Placed off pad, Wrong polarity, coplanarity, wrong part and so on. I still consider 1 component as 1 DPMO, but I track what caused the defect for my process improvement. | | | | In Answer to the original question | | we use under 100 DPM for SMT (for most assemblies). | | In some cases the DPM will Fluctuate from Assembly to assembly due to poor layout, design, inferior components (I'm finger pointing here, there's no way it could be engineering) and so on. | | | | | | Well that�s my 2 cents | | | | Mike | | | | Mike, pretty sound observations and opinions. I agree, but then again I come from the 'manufacturing' side of things with a very careful eye out for our quality and process controls. Try convincing our QA and upper management on that and, hey !! | | Oh well. Again, kudos! | Another thing to consider is where the defect data is being collected. The defect rate at SMT inspection / touchup prior to delivery to the next customer will usually be higher than the rate reported by the next customer -- say In Circuit Test. A contract manufacturer may have a goal of less than 100 defects per million parts placed, as reported by their customer, however, their internal defects that are caught and repaired prior to any electrical test may be 10x higher, and it may be hard to get that information. I'd be happy to see multiple sources report in this thread, the defect rate (per million parts placed)at the first electrical test after SMT assembly, where any defects are related to the SMT process. Several years ago I heard that number was 400 dpm. Now, I'm gussing it's 100, or even less. ANYONE WANT TO SHARE THE GOAL DPM?

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