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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Cylindrical diodes Missing during SMT process.

#9975

Cylindrical diodes Missing during SMT process. | 24 August, 1999

Hello everyone, We found many cylindrical diodes missing during SMT process. Could someone tell us how to prevent this problem? Is it effective to change the shape of stencil apture or reduce fan speed in reflow oven? Thanks in advance.

Gyver

reply »

Scott Davies

#9976

Re: Cylindrical diodes Missing during SMT process. | 24 August, 1999

| Hello everyone, | We found many cylindrical diodes missing during SMT process. Could someone tell us how to prevent this problem? Is it effective to change the shape of stencil apture or reduce fan speed in reflow oven? Thanks in advance. | | Gyver | Are you talking MELF or Mini-MELF diodes here? A while back, we had a spate of Mini-MELF 4148 diodes failing to place. It turned out that the components were sticking in the pockets of the packaging tape, probably because the manufacturer had packaged them before the ink printed on them had properly dried. So, check that the parts are definitely in place before the boards go through reflow. If they are, make sure that pad sizes are big enough, and you are putting down enough paste (0.006" thick stencil will be fine). Another problem we have encountered in the past is contamination of the components end caps, leading to poor solderability. This may be something you would want to investigate too.

Best of Luck Scott

reply »

George Verboven

#9977

Re: Cylindrical diodes Missing during SMT process. | 24 August, 1999

| | Hello everyone, | | We found many cylindrical diodes missing during SMT process. Could someone tell us how to prevent this problem? Is it effective to change the shape of stencil apture or reduce fan speed in reflow oven? Thanks in advance. | | | | Gyver | | | Are you talking MELF or Mini-MELF diodes here? A while back, we had a spate of Mini-MELF 4148 diodes failing to place. It turned out that the components were sticking in the pockets of the packaging tape, probably because the manufacturer had packaged them before the ink printed on them had properly dried. So, check that the parts are definitely in place before the boards go through reflow. If they are, make sure that pad sizes are big enough, and you are putting down enough paste (0.006" thick stencil will be fine). Another problem we have encountered in the past is contamination of the components end caps, leading to poor solderability. This may be something you would want to investigate too. | | Best of Luck | Scott | Some time ago, logistic told me that there where to many rejected Minimelfs.... So I went to the production floor and immediately started to check equipment. First I was checking indeed of it was stocked in the pockets than if there was enough vacuum, the shape or dimension of the pickup nozzle and finaly the vision camera..... Everything seems to be normal. Then I found out that I was approaching the problem wrong. Stupid me.... I reacted to quickly on the request of logistiek. It was not minimelf, who caused the problem, but it was the glass minimelf (diode) And that was not what i checked� I only checked the resistor� So what was the problem� The clearness of the VISION light was to high, so the shape looked like an hourglass shape� which was of course rejected. Good luck and take time to approach the problem.

reply »

#9978

Re: Cylindrical diodes Missing during SMT process. | 24 August, 1999

| | | Hello everyone, | | | We found many cylindrical diodes missing during SMT process. Could someone tell us how to prevent this problem? Is it effective to change the shape of stencil apture or reduce fan speed in reflow oven? Thanks in advance. | | | | | | Gyver | | | | | Are you talking MELF or Mini-MELF diodes here? A while back, we had a spate of Mini-MELF 4148 diodes failing to place. It turned out that the components were sticking in the pockets of the packaging tape, probably because the manufacturer had packaged them before the ink printed on them had properly dried. So, check that the parts are definitely in place before the boards go through reflow. If they are, make sure that pad sizes are big enough, and you are putting down enough paste (0.006" thick stencil will be fine). Another problem we have encountered in the past is contamination of the components end caps, leading to poor solderability. This may be something you would want to investigate too. | | | | Best of Luck | | Scott | | | Some time ago, logistic told me that there where to many rejected Minimelfs.... | So I went to the production floor and immediately started to check equipment. | First I was checking indeed of it was stocked in the pockets than if there was enough vacuum, the shape or dimension of the pickup nozzle and finaly the vision camera..... | Everything seems to be normal. Then I found out that I was approaching the problem wrong. | Stupid me.... I reacted to quickly on the request of logistiek. | It was not minimelf, who caused the problem, but it was the glass minimelf (diode) | And that was not what i checked?I only checked the resistor? | So what was the problem?The clearness of the VISION light was to high, so the shape looked like an hourglass shape?which was of course rejected. | Good luck and take time to approach the problem. | | | Hello, Firstly, thanks for your responses. What I'm talking is glass MELF. Is it possible that diodes left solder pads during fast moving of pick and place process? Thanks again!

Gyver

reply »

Jimmy G

#9979

Re: Cylindrical diodes Missing during SMT process. | 24 August, 1999

| | | | Hello everyone, | | | | We found many cylindrical diodes missing during SMT process. Could someone tell us how to prevent this problem? Is it effective to change the shape of stencil apture or reduce fan speed in reflow oven? Thanks in advance. | | | | | | | | Gyver | | | | | | | Are you talking MELF or Mini-MELF diodes here? A while back, we had a spate of Mini-MELF 4148 diodes failing to place. It turned out that the components were sticking in the pockets of the packaging tape, probably because the manufacturer had packaged them before the ink printed on them had properly dried. So, check that the parts are definitely in place before the boards go through reflow. If they are, make sure that pad sizes are big enough, and you are putting down enough paste (0.006" thick stencil will be fine). Another problem we have encountered in the past is contamination of the components end caps, leading to poor solderability. This may be something you would want to investigate too. | | | | | | Best of Luck | | | Scott | | | | | Some time ago, logistic told me that there where to many rejected Minimelfs.... | | So I went to the production floor and immediately started to check equipment. | | First I was checking indeed of it was stocked in the pockets than if there was enough vacuum, the shape or dimension of the pickup nozzle and finaly the vision camera..... | | Everything seems to be normal. Then I found out that I was approaching the problem wrong. | | Stupid me.... I reacted to quickly on the request of logistiek. | | It was not minimelf, who caused the problem, but it was the glass minimelf (diode) | | And that was not what i checked?I only checked the resistor? | | So what was the problem?The clearness of the VISION light was to high, so the shape looked like an hourglass shape?which was of course rejected. | | Good luck and take time to approach the problem. | | | | | | | Hello, | Firstly, thanks for your responses. | What I'm talking is glass MELF. Is it possible that diodes left solder pads during fast moving of pick and place process? | Thanks again! | | Gyver | One of the things you could try (providing you have the capapbility) is to place a single dot of epoxy under the part.

If this is not an option, placing them last at the high spedd placement process may be an acceptable solution

reply »

Ian T

#9980

Re: Cylindrical diodes Missing during SMT process. | 24 August, 1999

| | | | | Hello everyone, | | | | | We found many cylindrical diodes missing during SMT process. Could someone tell us how to prevent this problem? Is it effective to change the shape of stencil apture or reduce fan speed in reflow oven? Thanks in advance. | | | | | | | | | | Gyver | | | | | | | | | Are you talking MELF or Mini-MELF diodes here? A while back, we had a spate of Mini-MELF 4148 diodes failing to place. It turned out that the components were sticking in the pockets of the packaging tape, probably because the manufacturer had packaged them before the ink printed on them had properly dried. So, check that the parts are definitely in place before the boards go through reflow. If they are, make sure that pad sizes are big enough, and you are putting down enough paste (0.006" thick stencil will be fine). Another problem we have encountered in the past is contamination of the components end caps, leading to poor solderability. This may be something you would want to investigate too. | | | | | | | | Best of Luck | | | | Scott | | | | | | | Some time ago, logistic told me that there where to many rejected Minimelfs.... | | | So I went to the production floor and immediately started to check equipment. | | | First I was checking indeed of it was stocked in the pockets than if there was enough vacuum, the shape or dimension of the pickup nozzle and finaly the vision camera..... | | | Everything seems to be normal. Then I found out that I was approaching the problem wrong. | | | Stupid me.... I reacted to quickly on the request of logistiek. | | | It was not minimelf, who caused the problem, but it was the glass minimelf (diode) | | | And that was not what i checked?I only checked the resistor? | | | So what was the problem?The clearness of the VISION light was to high, so the shape looked like an hourglass shape?which was of course rejected. | | | Good luck and take time to approach the problem. | | | | | | | | | | | Hello, | | Firstly, thanks for your responses. | | What I'm talking is glass MELF. Is it possible that diodes left solder pads during fast moving of pick and place process? | | Thanks again! | | | | Gyver | | | One of the things you could try (providing you have the capapbility) is to place a single dot of epoxy under the part. | | If this is not an option, placing them last at the high spedd placement process may be an acceptable solution | g'day first check the vision camera to make sure that the system sees the part, then check the tack of your paiste to make sure the part sticks. You might have to slow down the shape code. i place them with a fuji FIP3. I had to get a special nozzle for them. because the diodes are round they roll on the nozzle after pick up, specialy during high speed operation. If you are using a fuji FCP6 there are nozzles designed for melfs.

hope this helps

reply »

Scott Cook

#9981

Re: Cylindrical diodes Missing during SMT process. | 24 August, 1999

| Hello everyone, | We found many cylindrical diodes missing during SMT process. Could someone tell us how to prevent this problem? Is it effective to change the shape of stencil apture or reduce fan speed in reflow oven? Thanks in advance. | | Gyver |

Ah, the magic of MELF's and Mini-MELFS.....such fond, fond memories.

Gyver, if this is an issue where you are physically placing them, yet they are missing........chances are they are rolling.

The industry now offers the MELF package with square or rectangular terminations, rather than round. It solved all my problems about 3 years ago with MELFS. Nothing else did, and I tried apertures, paste, glue, and pad geometry.

Scott Cook

reply »

#9982

Re: Cylindrical diodes Missing during SMT process. | 25 August, 1999

| | | | | | Hello everyone, | | | | | | We found many cylindrical diodes missing during SMT process. Could someone tell us how to prevent this problem? Is it effective to change the shape of stencil apture or reduce fan speed in reflow oven? Thanks in advance. | | | | | | | | | | | | Gyver | | | | | | | | | | | Are you talking MELF or Mini-MELF diodes here? A while back, we had a spate of Mini-MELF 4148 diodes failing to place. It turned out that the components were sticking in the pockets of the packaging tape, probably because the manufacturer had packaged them before the ink printed on them had properly dried. So, check that the parts are definitely in place before the boards go through reflow. If they are, make sure that pad sizes are big enough, and you are putting down enough paste (0.006" thick stencil will be fine). Another problem we have encountered in the past is contamination of the components end caps, leading to poor solderability. This may be something you would want to investigate too. | | | | | | | | | | Best of Luck | | | | | Scott | | | | | | | | | Some time ago, logistic told me that there where to many rejected Minimelfs.... | | | | So I went to the production floor and immediately started to check equipment. | | | | First I was checking indeed of it was stocked in the pockets than if there was enough vacuum, the shape or dimension of the pickup nozzle and finaly the vision camera..... | | | | Everything seems to be normal. Then I found out that I was approaching the problem wrong. | | | | Stupid me.... I reacted to quickly on the request of logistiek. | | | | It was not minimelf, who caused the problem, but it was the glass minimelf (diode) | | | | And that was not what i checked?I only checked the resistor? | | | | So what was the problem?The clearness of the VISION light was to high, so the shape looked like an hourglass shape?which was of course rejected. | | | | Good luck and take time to approach the problem. | | | | | | | | | | | | | | | Hello, | | | Firstly, thanks for your responses. | | | What I'm talking is glass MELF. Is it possible that diodes left solder pads during fast moving of pick and place process? | | | Thanks again! | | | | | | Gyver | | | | | One of the things you could try (providing you have the capapbility) is to place a single dot of epoxy under the part. | | | | If this is not an option, placing them last at the high spedd placement process may be an acceptable solution | | | g'day | first check the vision camera to make sure that the system sees the part, then check the tack of your paiste to make sure the part sticks. You might have to slow down the shape code. | i place them with a fuji FIP3. I had to get a special nozzle for them. because the diodes are round they roll on the nozzle after pick up, specialy during high speed operation. If you are using a fuji FCP6 there are nozzles designed for melfs. | | hope this helps | Hello guys, Thanks for all your opinions and experiences. I think every solution will contribute to our company very much!

Gyver

reply »

JAX

#9983

Re: Cylindrical diodes Missing during SMT process. | 26 August, 1999

| | | | | | | Hello everyone, | | | | | | | We found many cylindrical diodes missing during SMT process. Could someone tell us how to prevent this problem? Is it effective to change the shape of stencil apture or reduce fan speed in reflow oven? Thanks in advance. | | | | | | | | | | | | | | Gyver | Something you might want to know: I assume that you do not have time to sit out on the floor and check every board before reflow. When checking the machine to see whether or not the vision system is finding the part one thing is normally overlooked. These are made of glass, and virtually always have stripes on each side before the contacts. These stripes confuse the vision system of most machines ( depending on the algorithm you are using ) and offset the end of the part. This causes the part's contacts to sit on an area of the board where there is no paste. This might be somthing you want to look into.

reply »

 Reflow System

Cogiscan Track Trace Control