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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Tombstone

Edmund S. Molina

#4191

Tombstone | 10 May, 2000

How to avoid tombstoning of film capacitors. The temperature profile is within standard/specifications, printing is good and placement is okay but tombstoning of film capacitor still occur. I need your help. Thank you.

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#4192

Re: Tombstone | 11 May, 2000

Hi, Your solder land it`s OK? Send me the dimensions of the solder land and the capacitor n.� of componentes in the PCB and the dimension of the PCB for trying help you. Sory my bad English. �ngelo

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Micah Newcomb

#4193

Re: Tombstone | 11 May, 2000

placement is only ok?, what size chip is this? Is the pad spacing correct? Are the apertures on your stencil reduced or 1:1. Stencil thickness? Do the problem areas heat up evenly? special plating on terminals of cap? Need more info.

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Dason C

#4194

Re: Tombstone | 31 May, 2000

I learn from Senju Metal, they have a formula with certain percent of Ag and Cu can elimate the tombstone. The hint is the eutectic only one reflow and the new material have two reflow.

Please let me know your result.

Rgds. Dason

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Arturo

#4195

Re: Tombstone | 31 May, 2000

I�m also having this problem with Panasonic film capacitor. Even when I have the correct pad size according to Panasonic data sheet the tombstoning occur. I am thinking that the problem could be the plating of the film capacitor. The only way I could reduce tombstoning was reducing aperture size on this component but still have a little tombstoning. Now we are tracking every reel we mount to check if there is any lot/tombstoning relation. What kind of film capacitor are you using? Panasonic? Component size? Terminal size?

Arturo.

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Jackie Hsieh

#4196

Re: Tombstone | 31 May, 2000

I think the reasons of the tombstone phenomenon could be concluded as follows: 1.The proper pad size,including the dimension of two pads,the gap of two pads. 2.The temperature distribution must be uniform (take care the shadow-effect) 3.The ramp-up slop of temperature profile should be smooth. 4.The apertures of stencil should be correctly. 5.The situtation of terminal coating is very important. 6.The good accuration of placement machine is necessary. 7.The increasing of melting point range sometimes have some benefits.

In my experince on that, the dimensions of layout pad is the root cause while the others are all right!

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