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

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SMT electronics assembly manufacturing forum.


park

#9200

reflow/cure/wave for double side assembly | 3 October, 1999

What are pro's and con's of reflowing top side first and curing bottom side chip components, and then wave soldering bottom side?

How about curing bottom side first and reflowing top side later?

What percentage of companies run reflow/cure/wave for double side board assembly (instead of cure/reflow/wave)?

What is your preference and why?

thanks Matthew

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JAX

#9201

Re: reflow/cure/wave for double side assembly | 3 October, 1999

| What are pro's and con's of reflowing top side first and curing bottom side chip components, and then wave soldering bottom side? | | How about curing bottom side first and reflowing top side later? | | What percentage of companies run reflow/cure/wave for double side board assembly (instead of cure/reflow/wave)? | | What is your preference and why? | | thanks | Matthew | | Matthew, One problem I would have with cure/reflow/wave, although I am sure others will have more, is the parts you cure would stay in process longer. This would make the possibility of missing components and handling issues increase drastically. You do not want parts that are only glued down waiting for flow/wave any longer than you have to. Thats just my opinion, I could be wrong. |

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Chris May

#9202

Re: reflow/cure/wave for double side assembly | 4 October, 1999

| What are pro's and con's of reflowing top side first and curing bottom side chip components, and then wave soldering bottom side? | | How about curing bottom side first and reflowing top side later? | | What percentage of companies run reflow/cure/wave for double side board assembly (instead of cure/reflow/wave)? | | What is your preference and why? | | thanks | Matthew | | Matthew, I agree with JAX. The longer your cured components are hanging around, the more chance there will be for getting knocked off during inevitable handling and storage. You may find that design have some chip caps or R's closer to the edge of a board than your storage racks will cope with. i.e. operators (bless 'em) slip the boards into horizontal racking only to be confronted by a shower of components. At least if there soldered they may notice some dificulty.

Regards,

Chris. |

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park kyung sam

#9203

Re: reflow/cure/wave for double side assembly | 4 October, 1999

| | What are pro's and con's of reflowing top side first and curing bottom side chip components, and then wave soldering bottom side? | | | | How about curing bottom side first and reflowing top side later? | | | | What percentage of companies run reflow/cure/wave for double side board assembly (instead of cure/reflow/wave)? | | | | What is your preference and why? | | | | thanks | | Matthew | | | | Matthew, | I agree with JAX. The longer your cured components are hanging around, the more chance there will be for getting knocked off during inevitable handling and storage. You may find that design have some chip caps or R's closer to the edge of a board than your storage racks will cope with. i.e. operators (bless 'em) slip the boards into horizontal racking only to be confronted by a shower of components. At least if there soldered they may notice some dificulty. | | Regards, | | Chris.

I don't like to do curing first if the b'd can be supported by back up pin during dispencing and there is no fine pitch parts(because of oxidation). To find the space for back up pin you can use transparent films. Curing first occurs more chip missing a lot than soldering first. As you know the objective of curing is to attach chips on b'd temporary for wave soldering. To control the bond m/c is the better way than to control homan error although there is a warpage on b'd after curing. i will do soldering first if it possible.(warpage,space for bonding) In my case I tried experiment many time. I even print bonds with screen printer to prove existing bond. (i thought first chip missing is lack of bond volume) . i am not trust the man(handling b'd).and the important thing is to check out the bond material itself. it occurs the bond holding chips was melted during wave soldering even though there is enough bond......

good luck

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