Instructions for Use of FR-4 Epoxy Board

(1) DRY (Dried Laminate) substrate dry-up occurs during the use of FR-4 epoxy board
Reason analysis : Dried Laminate, DRY is a very headache problem during the use of FR-4 epoxy board. There are different degrees. The severe plot is comprehensive dryness, and the milder occurs in the corners. It may be caused by poor compatibility of glass cloth’s coupling agent (Coupling Agent) with resin and poor Wet Out (adhesiveness). In addition, it may also be caused by overcure of the film so that the resin flows during lamination The performance is not good.If the Resin Flow R / F of the film is found to be low, it may be a precursor to the drying up of the substrate.DRY substrates are prone to delamination during the solderability test.
Countermeasure: In the process of using FR-4 epoxy board, if it is the problem of surface finish of glass cloth (Finish), you must ask the supplier to improve. If the glue flow is low, it can reduce the Varnish water. Gelation time (S / G), or increase the gelation time (P / G) and the gel content (R / C) of the film. If DRY is not serious, you can also modify the compression conditions, such as increasing Heating rate, increasing pressure in advance, increasing pressure, etc.However, this is a method of treating symptoms, and the effect is far less significant than the adjustment and improvement of materials.

(2) WAC / WAE (White at Corner, White at Edge) —It appears during the use of FR-4 epoxy board.
Cause analysis: During the use of FR-4 epoxy board, when the film’s rubber flow rate (R / F) is high or moisture is absorbed due to poor storage conditions, press flow is easy to occur during lamination When the film is heated, the resin diffuses from the center to the periphery in an anisotropic manner, so the edge flow glue is large, and the water content (R / C) of the glue is also lower. When it can’t be avoided completely, weave white corners and white edges will appear. Another possible reason is that the heating rate is too fast, which causes a large temperature difference in the outer layer inside each Book and uneven glue flow, which causes a slight slippage when pressed. In addition, there are many tiny bubbles and microvoids in the film. When the glue flow rate (R / F) is low, the bubbles are only driven to the edge of the board and cannot escape out of the board. Will also show white corners and edges.
Countermeasure: If the film flow rate (R / F) of the film is high during the use of FR-4 epoxy board, you can increase the gelation time (S / G) of Fan Lishui or reduce the gelation time of the film (P / G). And the larger glue can also be modified by the lamination conditions (such as reducing the heating rate, delaying the upward pressure, etc.). For example, the white corners and white edges can be changed due to low R / F. (Such as increasing R / C, P / G) or pressing parts (increasing pressure, increasing pressure, increasing heating rate, etc.).

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