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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Christopher Lampron

#13336

Conductive Epoxy | 3 December, 1998

Does anyone have any information or experience with the use of conductive epoxy in leu of solder. I have a unique application that might lend itself to this technology. I am looking for manufacturers, printing, curing and reliability info. Any information would be greatly appreciated.

Thanks in Advance Christopher Lampron

reply »

David Pinsky

#13337

Re: Conductive Epoxy | 3 December, 1998

| Does anyone have any information or experience with the use of conductive epoxy in leu of solder. I have a unique application that might lend itself to this technology. I am looking for manufacturers, printing, curing and reliability info. | Any information would be greatly appreciated. | | Thanks in Advance | Christopher Lampron |

In general you will require different finishes for reliable soldering and reliable conductive epoxy bonding. For example, solder and tin plate are excellent to solder to, but are a disaster to epoxy bond to. Most component vendors offer devices with a choice of finish. You should ask for the finish that is recco for epoxy (ususlly gold).

The adhesion of silver filled epoxies is far less than their un-filled varieties. Therefore, you don't want to use solely Ag-epoxy to affix big components. For big components you can use un-filled epoxy to bond the body, and filled epoxy for the contacts.

reply »

Earl Moon

#13338

Re: Conductive Epoxy | 3 December, 1998

| | Does anyone have any information or experience with the use of conductive epoxy in leu of solder. I have a unique application that might lend itself to this technology. I am looking for manufacturers, printing, curing and reliability info. | | Any information would be greatly appreciated. | | | | Thanks in Advance | | Christopher Lampron | | | | In general you will require different finishes for reliable soldering and reliable conductive epoxy bonding. For example, solder and tin plate are excellent to solder to, but are a disaster to epoxy bond to. Most component vendors offer devices with a choice of finish. You should ask for the finish that is recco for epoxy (ususlly gold). | | The adhesion of silver filled epoxies is far less than their un-filled varieties. Therefore, you don't want to use solely Ag-epoxy to affix big components. For big components you can use un-filled epoxy to bond the body, and filled epoxy for the contacts. | | Can you tell us if there is a problem with silver migration with epoxies?

Earl Moon

reply »

Ryan Jennens

#13339

Re: Conductive Epoxy | 3 December, 1998

| | Does anyone have any information or experience with the use of conductive epoxy in leu of solder. I have a unique application that might lend itself to this technology. I am looking for manufacturers, printing, curing and reliability info. | | Any information would be greatly appreciated. | | | | Thanks in Advance | | Christopher Lampron | | | | In general you will require different finishes for reliable soldering and reliable conductive epoxy bonding. For example, solder and tin plate are excellent to solder to, but are a disaster to epoxy bond to. Most component vendors offer devices with a choice of finish. You should ask for the finish that is recco for epoxy (ususlly gold). | | The adhesion of silver filled epoxies is far less than their un-filled varieties. Therefore, you don't want to use solely Ag-epoxy to affix big components. For big components you can use un-filled epoxy to bond the body, and filled epoxy for the contacts. | | Hey David-

How is the rework handled? Is it as difficult as it seems?

Ryan

reply »

Russ M

#13340

Re: Conductive Epoxy | 3 December, 1998

| | | Does anyone have any information or experience with the use of conductive epoxy in leu of solder. I have a unique application that might lend itself to this technology. I am looking for manufacturers, printing, curing and reliability info. | | | Any information would be greatly appreciated. | | | | | | Thanks in Advance | | | Christopher Lampron | | | | |

Christopher:

The flexible circuit manufacturers have been using silver filled epoxy for some years as a solder replacement. The comments I have read so far are germaine to the issues you face. The main issue is strength of the bond. If you are looking to bond a surface mount component by the lead to pad interface only, it can be done even on very large flat components. If you are trying to attach coils, transformers, chokes, etc, which have a high profile, then the strength of the epoxy may not be enough to handle the vector impact of any jarring force applied laterally to the component and shear the component from the board. The surface finish is important too. Copper, gold, bizmuth, tin, are all good bonding surfaces for epoxy. Remember, the silver fill is not 100% of the epoxy and therefore the epoxy material will stick to virtually every surface except teflon and mylar as a general rule. But, just because you have a strong bond does not mean that you will have a good electrical connection. I suggest you contact the following three companies technical support groups to aid you in choosing the right surface finishes and epoxies based upon your particular application: Ablestik in Rancho Domingez CA, or Polyflex in Cranston, RI, or Epotek (sorry, don't remember exactly where they are located). These three companies specialize in solder "look-a-like" Ag filled materials. I recommend Ablestik or Polyflex. I believe Ablestik's product number is 8175. Polyflex's product ID is Polysolder.

Someone in one of the responses asked about rework. It's a real bitch. It can be done if you plan ahead. Reworkable materials exist - called thermoplastics which are silver filled, form a good bond, and are reworkable by reheating. Hope this little dissertation helps. I spent 5 years in Advanced Materials for SMT from 1991-1996. | | In general you will require different finishes for reliable soldering and reliable conductive epoxy bonding. For example, solder and tin plate are excellent to solder to, but are a disaster to epoxy bond to. Most component vendors offer devices with a choice of finish. You should ask for the finish that is recco for epoxy (ususlly gold). | | | | The adhesion of silver filled epoxies is far less than their un-filled varieties. Therefore, you don't want to use solely Ag-epoxy to affix big components. For big components you can use un-filled epoxy to bond the body, and filled epoxy for the contacts. | | | | | Can you tell us if there is a problem with silver migration with epoxies? | | Earl Moon |

reply »

Jeff Sanchez

#13341

Re: Conductive Epoxy | 4 December, 1998

| | | | Does anyone have any information or experience with the use of conductive epoxy in leu of solder. I have a unique application that might lend itself to this technology. I am looking for manufacturers, printing, curing and reliability info. | | | | Any information would be greatly appreciated. | | | | | | | | Thanks in Advance | | | | Christopher Lampron | | | | | | | | | Christopher: | | The flexible circuit manufacturers have been using silver filled epoxy for some years as a solder replacement. The comments I have read so far are germaine to the issues you face. The main issue is strength of the bond. If you are looking to bond a surface mount component by the lead to pad interface only, it can be done even on very large flat components. If you are trying to attach coils, transformers, chokes, etc, which have a high profile, then the strength of the epoxy may not be enough to handle the vector impact of any jarring force applied laterally to the component and shear the component from the board. The surface finish is important too. Copper, gold, bizmuth, tin, are all good bonding surfaces for epoxy. Remember, the silver fill is not 100% of the epoxy and therefore the epoxy material will stick to virtually every surface except teflon and mylar as a general rule. But, just because you have a strong bond does not mean that you will have a good electrical connection. I suggest you contact the following three companies technical support groups to aid you in choosing the right surface finishes and epoxies based upon your particular application: Ablestik in Rancho Domingez CA, or Polyflex in Cranston, RI, or Epotek (sorry, don't remember exactly where they are located). These three companies specialize in solder "look-a-like" Ag filled materials. I recommend Ablestik or Polyflex. I believe Ablestik's product number is 8175. Polyflex's product ID is Polysolder. | | Someone in one of the responses asked about rework. It's a real bitch. It can be done if you plan ahead. Reworkable materials exist - called thermoplastics which are silver filled, form a good bond, and are reworkable by reheating. Hope this little dissertation helps. I spent 5 years in Advanced Materials for SMT from 1991-1996. | | | In general you will require different finishes for reliable soldering and reliable conductive epoxy bonding. For example, solder and tin plate are excellent to solder to, but are a disaster to epoxy bond to. Most component vendors offer devices with a choice of finish. You should ask for the finish that is recco for epoxy (ususlly gold). | | | | | | The adhesion of silver filled epoxies is far less than their un-filled varieties. Therefore, you don't want to use solely Ag-epoxy to affix big components. For big components you can use un-filled epoxy to bond the body, and filled epoxy for the contacts. | | | | | | | | Can you tell us if there is a problem with silver migration with epoxies? | | | | Earl Moon | | | | Hey guys,

I love a good concept! What I have found through looking at these epoxies as an alternative to standard bonding of solder (all metallurgy aside) is cost! I beleive the gentelmans first comments included that he had a bright new idea? The cost from what I can see would rule out 99% of standard aplications. It would be awsome if the price was right cause then we could all ditch our ovens and stream line our production down to some slick form of silk screaning and pick and place run it through a UV system and be done! The rework can then be handled prior to the UV curing? So it would seem. Wow , no more profiling. I can't remember the companies name that I contacted for the epoxy but it was hundreds of dallors for a small quantity. So when the price plummits down to my world I will be there like most, throwing away my oven.......LOL

Just my 3 cents................Jeff Sanchez

reply »

Jason

#13342

Re: Conductive Epoxy | 4 December, 1998

Jeff,

I used conductive epoxy for diebonding and chipcaps on hybrid xtal controlled osc. We were applying via stencil printer, then curing in a KME vertical cure, a real foot print saver. Even under controlled environmental conditions, it was a real pain to control. Viscosity was based entirely on temperature. Shear testing is a must. Per Earl's question, I haven't seen any problems with solids migration to speak of, but this wasn't my area of expertise. I will call up my old colleges over at Motorola and see if they will let me give out their email addresses. If so I will send you and Earl their addresses so you can pick their brains.

reply »

rick

#13343

Re: Conductive Epoxy | 7 December, 1998

| Does anyone have any information or experience with the use of conductive epoxy in leu of solder. I have a unique application that might lend itself to this technology. I am looking for manufacturers, printing, curing and reliability info. | Any information would be greatly appreciated. | | Thanks in Advance | Christopher Lampron | Christopher,

IF your looking for a way to apply a conductive adhesive Nordson Corporation In Ohio has developed a unique way to dispense it.Using jetting technology the Conductive material is shot onto the substraight eliminating any contact with the part thus eliminating and worrys of cracking the part, board warpage and time spent with Z-movements and wetting the surface you see with contact dispensers. This technology is ideal in the surface mount crystal world. Let me know if your interested or have any questions.

Rick

reply »

PCB X-Ray Inspection

SMT Custom Nozzles